Nurse jackie observes the newborns lack of respiratory effort

Chapter 3 Prenatal Development, Birth, and the Newborn Baby

An expectant mother reacts with amazement on hearing the robust heartbeat of her nearly full-term fetus. High-quality prenatal care and preparation for the events of childbirth enable her to approach labor and delivery with confidence and excitement.

chapter outline

· Prenatal Development

· Conception

· Period of the Zygote

· Period of the Embryo

· Period of the Fetus

· Prenatal Environmental Influences

· Teratogens

· Other Maternal Factors

· The Importance of Prenatal Health Care

· ■ SOCIAL ISSUES: HEALTH The Nurse–Family Partnership: Reducing Maternal Stress and Enhancing Child Development Through Social Support

· Childbirth

· The Stages of Childbirth

· The Baby’s Adaptation to Labor and Delivery

· The Newborn Baby’s Appearance

· Assessing the Newborn’s Physical Condition: The Apgar Scale

· Approaches to Childbirth

· Natural, or Prepared, Childbirth

· Home Delivery

· Medical Interventions

· Fetal Monitoring

· Labor and Delivery Medication

· Cesarean Delivery

· Preterm and Low-Birth-Weight Infants

· Preterm versus Small-for-Date Infants

· Consequences for Caregiving

· Interventions for Preterm Infants

· ■ SOCIAL ISSUES: HEALTH A Cross-National Perspective on Health Care and Other Policies for Parents and Newborn Babies

· Birth Complications, Parenting, and Resilience

· The Newborn Baby’s Capacities

· Reflexes

· States

· Sensory Capacities

· Neonatal Behavioral Assessment

· ■ BIOLOGY AND ENVIRONMENT The Mysterious Tragedy of Sudden Infant Death Syndrome

· Adjusting to the New Family Unit

When I met Yolanda and Jay one fall in my child development class, Yolanda was just two months pregnant. Approaching age 30, married for several years, and their careers well under way, they had decided to have a baby. To prepare for parenthood, they enrolled in my evening section, arriving once a week after work full of questions: “How does the baby grow before birth?” “When is each organ formed?” “Has its heart begun to beat?” “Can it hear, feel, or sense our presence?”

Most of all, Yolanda and Jay wanted to do everything possible to make sure their baby would be born healthy. Yolanda started to wonder about her diet and whether she should keep up her daily aerobic workout. And she asked me whether an aspirin for a headache, a glass of wine at dinner, or a few cups of coffee during work and study hours might be harmful.

In this chapter, we answer Yolanda and Jay’s questions, along with a great many more that scientists have asked about the events before birth. First, we trace prenatal development, paying special attention to environmental supports for healthy growth, as well as damaging influences that threaten the child’s health and survival. Next, we turn to the events of childbirth. Today, women in industrialized nations have many choices about where and how they give birth, and hospitals go to great lengths to make the arrival of a new baby a rewarding, family-centered event.

Yolanda and Jay’s son Joshua reaped the benefits of his parents’ careful attention to his needs during pregnancy. He was strong, alert, and healthy at birth. Nevertheless, the birth process does not always go smoothly. We will consider the pros and cons of medical interventions, such as pain-relieving drugs and surgical deliveries, designed to ease a difficult birth and protect the health of mother and baby. Our discussion also addresses the development of infants born underweight or too early. We conclude with a close look at the remarkable capacities of newborns.

Prenatal Development

The sperm and ovum that unite to form the new individual are uniquely suited for the task of reproduction. The ovum is a tiny sphere, measuring 1175 inch in diameter—barely visible to the naked eye as a dot the size of the period at the end of this sentence. But in its microscopic world, it is a giant—the largest cell in the human body. The ovum’s size makes it a perfect target for the much smaller sperm, which measure only 1500 inch.

Conception

About once every 28 days, in the middle of a woman’s menstrual cycle, an ovum bursts from one of her ovaries, two walnut-sized organs located deep inside her abdomen, and is drawn into one of two fallopian tubes—long, thin structures that lead to the hollow, soft-lined uterus (see Figure 3.1 ). While the ovum is traveling, the spot on the ovary from which it was released, now called the corpus luteum, secretes hormones that prepare the lining of the uterus to receive a fertilized ovum. If pregnancy does not occur, the corpus luteum shrinks, and the lining of the uterus is discarded two weeks later with menstruation.

The male produces sperm in vast numbers—an average of 300 million a day—in the testes, two glands located in the scrotum, sacs that lie just behind the penis. In the final process of maturation, each sperm develops a tail that permits it to swim long distances, upstream in the female reproductive tract, through the cervix (opening of the uterus) and into the fallopian tube, where fertilization usually takes place. The journey is difficult, and many sperm die. Only 300 to 500 reach the ovum, if one happens to be present. Sperm live for up to 6 days and can lie in wait for the ovum, which survives for only 1 day after being released into the fallopian tube. However, most conceptions result from intercourse occurring during a three-day period—on the day of ovulation or during the 2 days preceding it (Wilcox, Weinberg, & Baird, 1995 ).

With conception, the story of prenatal development begins to unfold. The vast changes that take place during the 38 weeks of pregnancy are usually divided into three phases: (1) the period of the zygote, (2) the period of the embryo, and (3) the period of the fetus. As we look at what happens in each, you may find it useful to refer to Table 3.1 , which summarizes milestones of prenatal development.

Period of the Zygote

FIGURE 3.1 Female reproductive organs, showing fertilization, early cell duplication, and implantation.

(From Before We Are Born, 6th ed., by K. L. Moore & T. V. N. Persaud, p. 87. Copyright © 2003, reprinted with permission from Elsevier, Inc.)

The period of the zygote lasts about two weeks, from fertilization until the tiny mass of cells drifts down and out of the fallopian tube and attaches itself to the wall of the uterus. The zygote’s first cell duplication is long and drawn out; it is not complete until about 30 hours after conception. Gradually, new cells are added at a faster rate. By the fourth day, 60 to 70 cells exist that form a hollow, fluid-filled ball called a blastocyst (refer again to Figure 3.1 ). The cells on the inside, called the embryonic disk, will become the new organism; the outer ring of cells, termed the trophoblast, will become the structures that provide protective covering and nourishment.

TABLE 3.1 Milestones of Prenatal Development

TRIMESTER

PERIOD

WEEKS

LENGTH AND WEIGHT

MAJOR EVENTS

First

Zygote

image1

1

2

The one-celled zygote multiplies and forms a blastocyst.

The blastocyst burrows into the uterine lining. Structures that feed and protect the developing organism begin to form—amnion, chorion, yolk sac, placenta, and umbilical cord.

Embryo

image2

3–4

5–8

¼ inch (6 mm)

1 inch (2.5 cm); 17ounce (4 g)

A primitive brain and spinal cord appear. Heart, muscles, ribs, backbone, and digestive tract begin to develop.

Many external body structures (face, arms, legs, toes, fingers) and internal organs form. The sense of touch begins to develop, and the embryo can move.

Fetus

image3

9–12

3 inches (7.6 cm); less than 1 ounce (28 g)

Rapid increase in size begins. Nervous system, organs, and muscles become organized and connected, and new behavioral capacities (kicking, thumb sucking, mouth opening, and rehearsal of breathing) appear. External genitals are well-formed, and the fetus’s sex is evident.

Second

image4

13–24

12 inches (30 cm); 1.8 pounds (820 g)

The fetus continues to enlarge rapidly. In the middle of this period, fetal movements can be felt by the mother. Vernix and lanugo keep the fetus’s skin from chapping in the amniotic fluid. Most of the brain’s neurons are in place by 24 weeks. Eyes are sensitive to light, and the fetus reacts to sound.

Third

image5

25–38

20 inches (50 cm); 7.5 pounds (3,400 g)

The fetus has a good chance of survival if born during this time. Size increases. Lungs mature. Rapid brain development causes sensory and behavioral capacities to expand. In the middle of this period, a layer of fat is added under the skin. Antibodies are transmitted from mother to fetus to protect against disease. Most fetuses rotate into an upside-down position in preparation for birth.

Source: Moore, Persaud, & Torchia, 2013.

Photos (from top to bottom): © Claude Cortier/Photo Researchers, Inc.; © G. Moscoso/Photo

Researchers, Inc.; © John Watney/Photo Researchers, Inc.; © James Stevenson/Photo Researchers, Inc.; © Lennart Nilsson, A Child Is Born/Scanpix.

Implantation.

Between the seventh and ninth days, implantation occurs: The blastocyst burrows deep into the uterine lining. Surrounded by the woman’s nourishing blood, it starts to grow in earnest. At first, the trophoblast (protective outer layer) multiplies fastest. It forms a membrane, called the amnion , that encloses the developing organism in amniotic fluid, which helps keep the temperature of the prenatal world constant and provides a cushion against any jolts caused by the woman’s movement. A yolk sac emerges that produces blood cells until the liver, spleen, and bone marrow are mature enough to take over this function (Moore, Persaud, & Torchia, 2013 ).

The events of these first two weeks are delicate and uncertain. As many as 30 percent of zygotes do not survive this period. In some, the sperm and ovum do not join properly. In others, cell duplication never begins. By preventing implantation in these cases, nature eliminates most prenatal abnormalities (Sadler, 2010 ).

Period of the zygote: seventh to ninth day. The fertilized ovum duplicates rapidly, forming a hollow ball of cells, or blastocyst, by the fourth day after fertilization. Here the blastocyst, magnified thousands of times, burrows into the uterine lining between the seventh and ninth day.

The Placenta and Umbilical Cord.

By the end of the second week, cells of the trophoblast form another protective membrane—the chorion , which surrounds the amnion. From the chorion, tiny hairlike villi, or blood vessels, emerge. 1 As these villi burrow into the uterine wall, the placenta starts to develop. By bringing the embryo’s and mother’s blood close together, the placenta permits food and oxygen to reach the organism and waste products to be carried away. A membrane forms that allows these substances to be exchanged but prevents the mother’s and embryo’s blood from mixing directly.

The placenta is connected to the developing organism by the umbilical cord , which first appears as a tiny stalk and, during the course of pregnancy, grows to a length of 1 to 3 feet. The umbilical cord contains one large vein that delivers blood loaded with nutrients and two arteries that remove waste products. The force of blood flowing through the cord keeps it firm, so it seldom tangles while the embryo, like a space-walking astronaut, floats freely in its fluid-filled chamber (Moore, Persaud, & Torchia, 2013 ).

By the end of the period of the zygote, the developing organism has found food and shelter. These dramatic beginnings take place before most mothers know they are pregnant.

Period of the Embryo

The period of the embryo lasts from implantation through the eighth week of pregnancy. During these brief six weeks, the most rapid prenatal changes take place as the groundwork is laid for all body structures and internal organs.

Last Half of the First Month.

In the first week of this period, the embryonic disk forms three layers of cells: (1) the ectoderm, which will become the nervous system and skin; (2) the mesoderm, from which will develop the muscles, skeleton, circulatory system, and other internal organs; and (3) the endoderm, which will become the digestive system, lungs, urinary tract, and glands. These three layers give rise to all parts of the body.

At first, the nervous system develops fastest. The ectoderm folds over to form the neural tube , or primitive spinal cord. At 3½ weeks, the top swells to form the brain. While the nervous system is developing, the heart begins to pump blood, and the muscles, backbone, ribs, and digestive tract appear. At the end of the first month, the curled embryo—only ¼ inch long—consists of millions of organized groups of cells with specific functions.

The Second Month.

In the second month, growth continues rapidly. The eyes, ears, nose, jaw, and neck form. Tiny buds become arms, legs, fingers, and toes. Internal organs are more distinct: The intestines grow, the heart develops separate chambers, and the liver and spleen take over production of blood cells so that the yolk sac is no longer needed. Changing body proportions cause the embryo’s posture to become more upright.

Period of the embryo: fourth week. This 4-week-old embryo is only ¼-inch long, but many body structures have begun to form. The primitive tail will disappear by the end of the embryonic period.

1Recall from Table 2.4 on page 56 that chorionic villus sampling is the prenatal diagnostic method that can be performed earliest, at nine weeks after conception.

Period of the embryo: seventh week. The embryo’s posture is more upright. Body structures—eyes, nose, arms, legs, and internal organs—are more distinct. An embryo this age responds to touch. It can also move, although at less than one inch long and one ounce in weight, it is till too tiny to be felt by the mother.

At 7 weeks, production of neurons (nerve cells that store and transmit information) begins deep inside the neural tube at the astounding pace of more than 250,000 per minute (Nelson, 2011 ). Once formed, neurons begin traveling along tiny threads to their permanent locations, where they will form the major parts of the brain.

At the end of this period, the embryo—about 1 inch long and 17 ounce in weight—can already sense its world. It responds to touch, particularly in the mouth area and on the soles of the feet. And it can move, although its tiny flutters are still too light to be felt by the mother (Moore, Persaud, & Torchia, 2013 ).

Period of the Fetus

The period of the fetus , from the ninth week to the end of pregnancy, is the longest prenatal period. During this “growth and finishing” phase, the organism increases rapidly in size.

The Third Month.

In the third month, the organs, muscles, and nervous system start to become organized and connected. When the brain signals, the fetus kicks, bends its arms, forms a fist, curls its toes, turns its head, opens its mouth, and even sucks its thumb, stretches, and yawns. Body position changes occur as often as 25 times per hour (Einspieler, Marschik, & Prechtl, 2008 ). The tiny lungs begin to expand and contract in an early rehearsal of breathing movements. By the twelfth week, the external genitals are well-formed, and the sex of the fetus can be detected with ultrasound (Sadler, 2010 ). Other finishing touches appear, such as fingernails, toenails, tooth buds, and eyelids. The heartbeat can now be heard through a stethoscope.

Prenatal development is sometimes divided into trimesters , or three equal time periods. At the end of the third month, the first trimester is complete.

The Second Trimester.

By the middle of the second trimester, between 17 and 20 weeks, the new being has grown large enough that the mother can feel its movements. A white, cheeselike substance called vernix protects its skin from chapping during the long months spent bathing in the amniotic fluid. White, downy hair called lanugo also appears over the entire body, helping the vernix stick to the skin.

At the end of the second trimester, many organs are well-developed. And most of the brain’s billions of neurons are in place; few will be produced after this time. However, glial cells, which support and feed the neurons, continue to increase rapidly throughout the remaining months of pregnancy, as well as after birth. Consequently, brain weight increases tenfold from the twentieth week until birth (Roelfsema et al., 2004 ). At the same time, neurons begin forming synapses, or connections, at a rapid pace.

Period of the fetus: eleventh week. The fetus grows rapidly. At 11 weeks, the brain and muscles are better connected. The fetus can kick, bend its arms, and open and close its hands and mouth, and suck its thumb. Notice the yolk sac, which shrinks as the internal organs take over its function of producing blood cells.

Brain growth means new behavioral capacities. The 20-week-old fetus can be stimulated as well as irritated by sounds. And if a doctor looks inside the uterus using fetoscopy (see Table 2.4 on page 56 ), fetuses try to shield their eyes from the light with their hands, indicating that sight has begun to emerge (Moore, Persaud, & Torchia, 2013 ). Still, a fetus born at this time cannot survive. Its lungs are immature, and the brain cannot yet control breathing and body temperature.

The Third Trimester.

During the final trimester, a fetus born early has a chance for survival. The point at which the baby can first survive, called the age of viability , occurs sometime between 22 and 26 weeks (Moore, Persaud, & Torchia, 2013 ). A baby born between the seventh and eighth months, however, usually needs oxygen assistance to breathe. Although the brain’s respiratory center is now mature, tiny air sacs in the lungs are not yet ready to inflate and exchange carbon dioxide for oxygen.

The brain continues to make great strides. The cerebral cortex, the seat of human intelligence, enlarges. As neural connectivity and organization improve, the fetus spends more time awake. At 20 weeks, fetal heart rate reveals no periods of alertness. But by 28 weeks, fetuses are awake about 11 percent of the time, a figure that rises to 16 percent just before birth (DiPietro et al., 1996 ). Between 30 and 34 weeks, fetuses show rhythmic alternations between sleep and wakefulness that gradually increase in organization (Rivkees, 2003 ). Around this time, synchrony between fetal heart rate and motor activity peaks: A rise in heart rate is usually followed within 5 seconds by a burst of motor activity (DiPietro et al., 2006 ). These are clear signs that coordinated neural networks are beginning to form in the brain.

Period of the fetus: twenty-second week. This fetus is almost one foot long and weighs slightly more than one pound. Its movements can be felt easily by the mother and by other family members who place a hand on her abdomen. If born now, the fetus has a slim chance of surviving.

By the end of pregnancy, the fetus also takes on the beginnings of a personality. Fetal activity is linked to infant temperament. In one study, more active fetuses during the third trimester became 1-year-olds who could better handle frustration and 2-year-olds who were less fearful, in that they more readily interacted with toys and with an unfamiliar adult in a laboratory (DiPietro et al., 2002 ). Perhaps fetal activity is an indicator of healthy neurological development, which fosters adaptability in childhood. The relationships just described, however, are only modest. As we will see in Chapter 6 , sensitive caregiving can modify the temperaments of children who have difficulty adapting to new experiences.

Period of the fetus: thirty-sixth week. This fetus fills the uterus. To nourish it, the umbilical cord and placenta have grown large. Notice the vernix (a cheeselike substance) on the skin, which protects it from chapping. The fetus has accumulated fat to aid temperature regulation after birth. In two more weeks, it will be full-term.

The third trimester brings greater responsiveness to stimulation. Between 23 and 30 weeks, connections form between the cerebral cortex and brain regions involved in pain sensitivity. By this time, painkillers should be used in any surgical procedures (Lee et al., 2005 ). Around 28 weeks, fetuses blink their eyes in reaction to nearby sounds (Kisilevsky & Low, 1998 ; Saffran, Werker, & Werner, 2006 ). And at 30 weeks, fetuses presented with a repeated auditory stimulus against the mother’s abdomen initially react with a rise in heart rate and body movements. But over the next 5 to 6 minutes, responsiveness gradually declines, indicating habituation (adaptation) to the sound. If the stimulus is reintroduced after a 10-minute delay, heart rate falls off far more quickly (Dirix et al., 2009 ). This suggests that fetuses can remember for at least a brief period.

Within the next six weeks, fetuses distinguish the tone and rhythm of different voices and sounds. They show systematic heart rate changes to a male versus a female speaker, to the mother’s voice versus a stranger’s, to a stranger speaking their native language (English) versus a foreign language (Mandarin Chinese), and to a simple familiar melody (descending tones) versus an unfamiliar melody (ascending tones) (Granier-Deferre et al., 2003 ; Huotilainen et al., 2005 ; Kisilevsky et al., 2003 , 2009 ; Lecanuet et al., 1993 ). And in one clever study, mothers read aloud Dr. Seuss’s lively book The Cat in the Hat for the last six weeks of pregnancy. After birth, their infants learned to turn on recordings of the mother’s voice by sucking on nipples. They sucked hardest to hear The Cat in the Hat—the sound they had come to know while still in the womb (DeCasper & Spence, 1988).

In the final three months, the fetus gains more than 5 pounds and grows 7 inches. In the eighth month, a layer of fat is added to assist with temperature regulation. The fetus also receives antibodies from the mother’s blood that protect against illnesses, since the newborn’s own immune system will not work well until several months after birth. In the last weeks, most fetuses assume an upside-down position, partly because of the shape of the uterus and also because the head is heavier than the feet. Growth slows, and birth is about to take place.

ASK YOURSELF

REVIEW Why is the period of the embryo regarded as the most dramatic prenatal period? Why is the period of the fetus called the “growth and finishing” phase?

CONNECT How is brain development related to fetal capacities and behavior?

APPLY Amy, two months pregnant, wonders how the embryo is being fed and what parts of the body have formed. “I don’t look pregnant yet, so does that mean not much development has taken place?” she asks. How would you respond to Amy?

image6 Prenatal Environmental Influences

Although the prenatal environment is far more constant than the world outside the womb, many factors can affect the embryo and fetus. Yolanda and Jay learned that parents—and society as a whole—can do a great deal to create a safe environment for development before birth.

Teratogens

The term teratogen refers to any environmental agent that causes damage during the prenatal period.Scientists chose this label (from the Greek word teras, meaning “malformation” or “monstrosity”) because they first learned about harmful prenatal influences from cases in which babies had been profoundly damaged. But the harm done by teratogens is not always simple and straightforward. It depends on the following factors:

· ● Dose. As we discuss particular teratogens, you will see that larger doses over longer time periods usually have more negative effects.

· ● Heredity. The genetic makeup of the mother and the developing organism plays an important role. Some individuals are better able than others to withstand harmful environments.

· ● Other negative influences. The presence of several negative factors at once, such as additional teratogens, poor nutrition, and lack of medical care, can worsen the impact of a harmful agent.

· ● Age. The effects of teratogens vary with the age of the organism at time of exposure. To understand this last idea, think of the sensitive period concept introduced in Chapter 1 . A sensitive period is a limited time span in which a part of the body or a behavior is biologically prepared to develop rapidly. During that time, it is especially sensitive to its surroundings. If the environment is harmful, then damage occurs, and recovery is difficult and sometimes impossible.

Figure 3.2 on page 86 summarizes prenatal sensitive periods. In the period of the zygote, before implantation, teratogens rarely have any impact. If they do, the tiny mass of cells is usually so damaged that it dies. The embryonic period is the time when serious defects are most likely to occur because the foundations for all body parts are being laid down. During the fetal period, teratogenic damage is usually minor. However, organs such as the brain, ears, eyes, teeth, and genitals can still be strongly affected.

The effects of teratogens go beyond immediate physical damage. Some health effects are delayed and may not show up for decades. Furthermore, psychological consequences may occur indirectly, as a result of physical damage. For example, a defect resulting from drugs the mother took during pregnancy can affect others’ reactions to the child as well as the child’s ability to explore the environment. Over time, parent–child interaction, peer relations, and cognitive, emotional, and social development may suffer. Furthermore, prenatally exposed children may be less resilient in the face of environmental risks, such as single parenthood, parental emotional disturbance, or maladaptive parenting (Yumoto, Jacobson, & Jacobson, 2008 ). As a result, their long-term adjustment may be compromised.

FIGURE 3.2 Sensitive periods in prenatal development.

Each organ or structure has a sensitive period, during which its development may be disturbed. Blue horizontal bars indicate highly sensitive periods. Green horizontal bars indicate periods that are somewhat less sensitive to teratogens, although damage can occur.

(Adapted from Before We Are Born, 7th ed., by K. L. Moore and T. V. N. Persaud, p. 313. Copyright © 2008, reprinted with permission from Elsevier, Inc.)

Notice how an important idea about development discussed in earlier chapters is at work here: bidirectional influences between child and environment. Now let’s look at what scientists have discovered about a variety of teratogens.

Prescription and Nonprescription Drugs.

In the early 1960s, the world learned a tragic lesson about drugs and prenatal development. At that time, a sedative called thalidomide was widely available in Canada, Europe, and South America. When taken by mothers 4 to 6 weeks after conception, thalidomide produced gross deformities of the embryo’s arms and legs and, less frequently, damage to the ears, heart, kidneys, and genitals. About 7,000 infants worldwide were affected (Moore, Persaud, & Torchia, 2013 ). As children exposed to thalidomide grew older, many scored below average in intelligence. Perhaps the drug damaged the central nervous system directly. Or the child-rearing conditions of these severely deformed youngsters may have impaired their intellectual development.

Another medication, a synthetic hormone called diethylstilbestrol (DES), was widely prescribed between 1945 and 1970 to prevent miscarriages. As daughters of these mothers reached adolescence and young adulthood, they showed unusually high rates of cancer of the vagina, malformations of the uterus, and infertility. When they tried to have children, their pregnancies more often resulted in prematurity, low birth weight, and miscarriage than those of non-DES-exposed women. Young men showed an increased risk of genital abnormalities and cancer of the testes (Goodman, Schorge, & Greene, 2011 ; Hammes & Laitman, 2003 ).

Currently, the most widely used potent teratogen is a vitamin A derivative called Accutane (known by the generic name isotretinoin), prescribed to treat severe acne and taken by hundreds of thousands of women of childbearing age in industrialized nations. Exposure during the first trimester results in eye, ear, skull, brain, heart, and immune system abnormalities (Honein, Paulozzi, & Erickson, 2001 ). Accutane’s packaging warns users to avoid pregnancy by using two methods of birth control, but many women do not heed this advice (Garcia-Bournissen et al., 2008 ).

Indeed, any drug with a molecule small enough to penetrate the placental barrier can enter the embryonic or fetal bloodstream. Yet many pregnant women continue to take over-the-counter medications without consulting their doctors. Aspirin is one of the most common. Several studies suggest that regular aspirin use is linked to low birth weight, infant death around the time of birth, poorer motor development, and lower intelligence scores in early childhood, although other research fails to confirm these findings (Barr et al., 1990 ; Kozer et al., 2003 ; Streissguth et al., 1987 ). Coffee, tea, cola, and cocoa contain another frequently consumed drug, caffeine. High doses increase the risk of low birth weight (Brent, Christian, & Diener, 2011 ). And persistent intake of antidepressant medication is linked to an elevated incidence of premature delivery and birth complications, including respiratory distress, and to high blood pressure in infancy (Lund, Pedersen, & Henriksen, 2009 ; Roca et al., 2011 ; Udechuku et al., 2010 ).

Because children’s lives are involved, we must take findings like these seriously. At the same time, we cannot be sure that these frequently used drugs actually cause the problems just mentioned. Often mothers take more than one drug. If the embryo or fetus is injured, it is hard to tell which drug might be responsible or whether other factors correlated with drug taking are at fault. Until we have more information, the safest course of action is the one Yolanda took: Avoid these drugs entirely. Unfortunately, many women do not know that they are pregnant during the early weeks of the embryonic period, when exposure to medications (and other teratogens) can be of greatest threat.

Illegal Drugs.

The use of highly addictive mood-altering drugs, such as cocaine and heroin, has become more widespread, especially in poverty-stricken inner-city areas, where these drugs provide a temporary escape from a daily life of hopelessness. Nearly 4 percent of U.S. pregnant women take these substances (Substance Abuse and Mental Health Services Administration, 2011 ).

Babies born to users of cocaine, heroin, or methadone (a less addictive drug used to wean people away from heroin) are at risk for a wide variety of problems, including prematurity, low birth weight, physical defects, breathing difficulties, and death around the time of birth (Bandstra et al., 2010 ; Howell, Coles, & Kable, 2008 ; Schuetze & Eiden, 2006 ). In addition, these infants are born drug-addicted. They are often feverish and irritable and have trouble sleeping, and their cries are abnormally shrill and piercing—a common symptom among stressed newborns (Bauer et al., 2005 ). When mothers with many problems of their own must care for these babies, who are difficult to calm down, cuddle, and feed, behavior problems are likely to persist.

Throughout the first year, heroin- and methadone-exposed infants are less attentive to the environment than nonexposed babies, and their motor development is slow. After infancy, some children get better, while others remain jittery and inattentive. The kind of parenting they receive may explain why problems persist for some but not for others (Hans & Jeremy, 2001 ).

Evidence on cocaine suggests that some prenatally exposed babies develop lasting difficulties. Cocaine constricts the blood vessels, causing oxygen delivered to the developing organism to fall for 15 minutes following a high dose. It also can alter the production and functioning of neurons and the chemical balance in the fetus’s brain. These effects may contribute to an array of cocaine-associated physical defects, including eye, bone, genital, urinary tract, kidney, and heart deformities; brain hemorrhages and seizures; and severe growth retardation (Covington et al., 2002 ; Feng, 2005 ; Salisbury et al., 2009 ). Several studies report perceptual, motor, attention, memory, language, and impulse-control problems that persist into the preschool and school years (Bandstra et al., 2011 ; Dennis et al., 2006 ; Lester & Lagasse, 2010 ; Linares et al., 2006 ).

This infant, born many weeks before his due date, breathes with the aid of a respirator. Prematurity and low birth weight can result from a variety of environmental influences during pregnancy, including maternal drug and tobacco use.

Other investigations, however, reveal no major negative effects of prenatal cocaine exposure (Behnke et al., 2006 ; Frank et al., 2005 ; Hurt et al., 2009 ). These contradictory findings indicate how difficult it is to isolate the precise damage caused by illegal drugs. Cocaine users vary greatly in the amount, potency, and purity of the cocaine they ingest. Also, they often take several drugs, display other high-risk behaviors, suffer from poverty and other stresses, and engage in insensitive caregiving—factors that worsen outcomes for children (Jones, 2006 ). But researchers have yet to determine exactly what accounts for findings of cocaine-related damage in some studies but not in others.

Another illegal drug, marijuana, is used more widely than heroin and cocaine. Researchers have linked prenatal marijuana exposure to smaller head size (a measure of brain growth); attention, memory, and academic achievement difficulties; impulsivity and overactivity; and depression as well as anger and aggression in childhood and adolescence (Goldschmidt et al., 2004 ; Gray et al., 2005 ; Huizink & Mulder, 2006 ; Jutras-Aswad et al., 2009 ). As with cocaine, however, lasting consequences are not well-established. Overall, the effects of illegal drugs are far less consistent than the impact of two legal substances to which we now turn: tobacco and alcohol.

Tobacco.

Although smoking has declined in Western nations, an estimated 14 percent of U.S. women smoke during their pregnancies (Tong et al., 2009 ). The best-known effect of smoking during the prenatal period is low birth weight. But the likelihood of other serious consequences, such as miscarriage, prematurity, cleft lip and palate, blood vessel abnormalities, impaired heart rate and breathing during sleep, infant death, and asthma and cancer later in childhood, also increases (Geerts et al., 2012 ; Howell, Coles, & Kable, 2008 ; Jaakkola & Gissler, 2004 ; Mossey et al., 2009 ). The more cigarettes a mother smokes, the greater the chances that her baby will be affected. And if a pregnant woman stops smoking at any time, even during the third trimester, she reduces the likelihood that her infant will be born underweight and suffer from future problems (Klesges et al., 2001 ).

Even when a baby of a smoking mother appears to be born in good physical condition, slight behavioral abnormalities may threaten the child’s development. Newborns of smoking mothers are less attentive to sounds, display more muscle tension, are more excitable when touched and visually stimulated, and more often have colic (persistent crying). These findings suggest subtle negative effects on brain development (Law et al., 2003 ; Sondergaard et al., 2002 ). Consistent with this view, prenatally exposed children and adolescents tend to have shorter attention spans, difficulties with impulsivity and overactivity, poorer memories, lower mental test scores, and higher levels of disruptive, aggressive behavior (Espy et al., 2011 ; Fryer, Crocker, & Mattson, 2008 ; Lindblad & Hjern, 2010 ).

Exactly how can smoking harm the fetus? Nicotine, the addictive substance in tobacco, constricts blood vessels, lessens blood flow to the uterus, and causes the placenta to grow abnormally. This reduces the transfer of nutrients, so the fetus gains weight poorly. Also, nicotine raises the concentration of carbon monoxide in the bloodstreams of both mother and fetus. Carbon monoxide displaces oxygen from red blood cells, damaging the central nervous system and slowing body growth in the fetuses of laboratory animals (Friedman, 1996 ). Similar effects may occur in humans.

From one-third to one-half of nonsmoking pregnant women are “passive smokers” because their husbands, relatives, or co-workers use cigarettes. Passive smoking is also related to low birth weight, infant death, childhood respiratory illnesses, and possible long-term attention, learning, and behavior problems (Best, 2009 ; Pattenden et al., 2006 ). Clearly, expectant mothers should avoid smoke-filled environments.

Alcohol.

In his moving book The Broken Cord, Michael Dorris ( 1989 ), a Dartmouth College anthropology professor, described what it was like to rear his adopted son Abel (called Adam in the book), whose biological mother drank heavily throughout pregnancy and died of alcohol poisoning shortly after his birth. A Sioux Indian, Abel was born with fetal alcohol spectrum disorder (FASD) , a term that encompasses a range of physical, mental, and behavioral outcomes caused by prenatal alcohol exposure. Children with FASD are given one of three diagnoses, which vary in severity:

Left photo: This 5-year-old’s mother drank heavily during pregnancy. Her widely spaced eyes, thin upper lip, and flattened philtrum are typical of fetal alcohol syndrome (FAS). Right photo: This 12-year-old has the small head and facial abnormalities of FAS. She also shows the mental impairments and slow growth that accompany the disorder.

· 1. Fetal alcohol syndrome (FAS), distinguished by (a) slow physical growth, (b) a pattern of three facial abnormalities (short eyelid openings; a thin upper lip; a smooth or flattened philtrum, or indentation running from the bottom of the nose to the center of the upper lip), and (c) brain injury, evident in a small head and impairment in at least three areas of functioning—for example, memory, language and communication, attention span and activity level (overactivity), planning and reasoning, motor coordination, or social skills. Other defects—of the eyes, ears, nose, throat, heart, genitals, urinary tract, or immune system—may also be present. Abel was diagnosed as having FAS. As is typical for this disorder, his mother drank heavily throughout pregnancy.

· 2. Partial fetal alcohol syndrome (p-FAS), characterized by (a) two of the three facial abnormalities just mentioned and (b) brain injury, again evident in at least three areas of impaired functioning. Mothers of children with p-FAS generally drank alcohol in smaller quantities, and children’s defects vary with the timing and length of alcohol exposure. Furthermore, recent evidence suggests that paternal alcohol use around the time of conception can alter gene expression (see page 73 in Chapter 2 ), thereby contributing to symptoms (Ouko et al., 2009 ).

· 3. Alcohol-related neurodevelopmental disorder (ARND), in which at least three areas of mental functioning are impaired, despite typical physical growth and absence of facial abnormalities. Again, prenatal alcohol exposure, though confirmed, is less pervasive than in FAS (Chudley et al., 2005 ; Loock et al., 2005 ).

Even when provided with enriched diets, FAS babies fail to catch up in physical size during infancy and childhood. Mental impairment associated with all three FASD diagnoses is also permanent: In his teens and twenties, Abel Dorris had trouble concentrating and keeping a routine job, and he suffered from poor judgment. For example, he would buy something and not wait for change or would wander off in the middle of a task. He died at age 23, after being hit by a car.

The more alcohol a woman consumes during pregnancy, the poorer the child’s motor coordination, speed of information processing, reasoning, and intelligence and achievement test scores during the preschool and school years (Burden, Jacobson, & Jacobson, 2005 ; Korkman, Kettunen, & Autti-Raemoe, 2003 ; Mattson, Calarco, & Lang, 2006 ). In adolescence and early adulthood, FASD is associated with persisting attention and motor-coordination deficits, poor school performance, trouble with the law, inappropriate social and sexual behaviors, alcohol and drug abuse, and lasting mental health problems, including depression and high emotional reactivity to stress (Barr et al., 2006 ; Fryer, Crocker, & Mattson, 2008 ; Hellemans et al., 2010 ; Howell et al., 2006 ; Streissguth et al., 2004 ).

How does alcohol produce its devastating effects? First, it interferes with production and migration of neurons in the primitive neural tube. Brain-imaging research reveals reduced brain size, damage to many brain structures, and abnormalities in brain functioning, including the electrical and chemical activity involved in transferring messages from one part of the brain to another (Coles et al., 2011 ; Haycock, 2009 ). Second, the body uses large quantities of oxygen to metabolize alcohol. A pregnant woman’s heavy drinking draws away oxygen that the developing organism needs for cell growth.

About 25 percent of U.S. mothers report drinking at some time during their pregnancies. As with heroin and cocaine, alcohol abuse is higher in poverty-stricken women. On some Native-American reservations, the incidence of FAS is as high as 10 to 20 percent (Szlemko, Wood, & Thurman, 2006 ; Tong et al., 2009 ). Unfortunately, when affected girls later become pregnant, the poor judgment caused by the syndrome often prevents them from understanding why they themselves should avoid alcohol. Thus, the tragic cycle is likely to be repeated in the next generation.

How much alcohol is safe during pregnancy? Even mild drinking, less than one drink per day, is associated with reduced head size and body growth among children followed into adolescence (Jacobson et al., 2004 ; Martinez-Frias et al., 2004 ). Recall that other factors—both genetic and environmental—can make some fetuses more vulnerable to teratogens. Therefore, no amount of alcohol is safe. Couples planning a pregnancy and expectant mothers should avoid alcohol entirely.

This child’s deformities are linked to radiation exposure early in pregnancy, caused by the Chernobyl nuclear power plant disaster in 1986. She is also at risk for low intelligence and language and emotional disorders.

Radiation.

Defects due to ionizing radiation were tragically apparent in children born to pregnant women who survived the bombing of Hiroshima and Nagasaki during World War II. Similar abnormalities surfaced in the nine months following the 1986 Chernobyl, Ukraine, nuclear power plant accident. After each disaster, the incidence of miscarriage and babies born with underdeveloped brains, physical deformities, and slow physical growth rose dramatically (Double et al., 2011 ; Schull, 2003 ). Evacuation of residents in areas near the Japanese nuclear facility damaged by the March 2011 earthquake and tsunami was intended to prevent these devastating outcomes.

Even when a radiation-exposed baby seems normal, problems may appear later. For example, even low-level radiation, resulting from industrial leakage or medical X-rays, can increase the risk of childhood cancer (Fattibene et al., 1999 ). In middle childhood, prenatally exposed Chernobyl children had abnormal brain-wave activity, lower intelligence test scores, and rates of language and emotional disorders two to three times greater than those of nonexposed Russian children. Furthermore, the more tension parents reported, due to forced evacuation from their homes and worries about living in irradiated areas, the poorer their children’s emotional functioning (Loganovskaja & Loganovsky, 1999 ; Loganovsky et al., 2008 ). Stressful rearing conditions seemed to combine with the damaging effects of prenatal radiation to impair children’s development.

Environmental Pollution.

In industrialized nations, an astounding number of potentially dangerous chemicals are released into the environment. More than 75,000 are in common use in the United States, and many new pollutants are introduced each year. When 10 newborns were randomly selected from U.S. hospitals for analysis of umbilical cord blood, researchers uncovered a startling array of industrial contaminants—287 in all (Houlihan et al., 2005 ). They concluded that many babies are “born polluted” by chemicals that not only impair prenatal development but increase the chances of health problems and life-threatening diseases later on.

Certain pollutants cause severe prenatal damage. In the 1950s, an industrial plant released waste containing high levels of mercury into a bay providing seafood and water for the town of Minamata, Japan. Many children born at the time displayed physical deformities, mental retardation, abnormal speech, difficulty in chewing and swallowing, and uncoordinated movements. High levels of prenatal mercury exposure disrupt production and migration of neurons, causing widespread brain damage (Clarkson, Magos, & Myers, 2003 ; Hubbs-Tait et al., 2005 ). Prenatal mercury exposure from maternal seafood diets predicts deficits in speed of cognitive processing and motor, attention, and verbal test performance during the school years (Boucher et al., 2010 ; Debes et al., 2006 ). Pregnant women are wise to avoid eating long-lived predatory fish, such as swordfish, albacore tuna, and shark, which are heavily contaminated with mercury.

For many years, polychlorinated biphenyls (PCBs) were used to insulate electrical equipment until research showed that, like mercury, they entered waterways and the food supply. In Taiwan, prenatal exposure to high levels of PCBs in rice oil resulted in low birth weight, discolored skin, deformities of the gums and nails, brain-wave abnormalities, and delayed cognitive development (Chen & Hsu, 1994 ; Chen et al., 1994 ). Steady, low-level PCB exposure is also harmful. Women who frequently ate PCB-contaminated fish, compared with those who ate little or no fish, had infants with lower birth weights, smaller heads, persisting attention and memory difficulties, and lower intelligence test scores in childhood (Boucher, Muckle, & Bastien, 2009 ; Jacobson & Jacobson, 2003 ; Stewart et al., 2008 ).

Another teratogen, lead, is present in paint flaking off the walls of old buildings and in certain materials used in industrial occupations. High levels of prenatal lead exposure are related to prematurity, low birth weight, brain damage, and a wide variety of physical defects. Even at low levels, affected infants and children show slightly poorer mental and motor development (Bellinger, 2005 ; Jedrychowski et al., 2009 ).

Finally, prenatal exposure to dioxins—toxic compounds resulting from incineration—is linked to brain, immune system, and thyroid damage in babies and to an increased incidence of breast and uterine cancers in women, perhaps through altering hormone levels (ten Tusscher & Koppe, 2004 ). Even tiny amounts of dioxin in the paternal bloodstream cause a dramatic change in sex ratio of offspring: Affected men father nearly twice as many girls as boys (Ishihara et al., 2007 ). Dioxin seems to impair the fertility of Y-bearing sperm prior to conception.

Infectious Disease.

About 5 percent of women in industrialized nations catch an infectious disease while pregnant. Although most of these illnesses, such as the common cold, seem to have no impact, a few—as Table 3.2 illustrates—can cause extensive damage.

Viruses.

In the mid-1960s, a worldwide epidemic of rubella (three-day, or German, measles) led to the birth of more than 20,000 American babies with serious defects and to 13,000 fetal and newborn deaths. Consistent with the sensitive-period concept, the greatest damage occurs when rubella strikes during the embryonic period. More than 50 percent of infants whose mothers become ill during that time show deafness; eye deformities, including cataracts; heart, genital, urinary, intestinal, bone, and dental defects; and mental retardation. Infection during the fetal period is less harmful, but low birth weight, hearing loss, and bone defects may still occur. The organ damage inflicted by prenatal rubella often leads to lifelong health problems, including severe mental illness, diabetes, cardiovascular disease, and thyroid and immune-system dysfunction in adulthood (Brown, 2006 ; Duszak, 2009 ).

Routine vaccination in infancy and childhood has made new rubella outbreaks unlikely in industrialized nations. But an estimated 100,000 cases of prenatal infection continue to occur worldwide, primarily in developing countries in Africa and Asia with weak or absent immunization programs (Bale, 2009 ).

The human immunodeficiency virus (HIV), which can lead to acquired immune deficiency syndrome (AIDS), a disease that destroys the immune system, has infected increasing numbers of women over the past three decades. In developing countries, where 95 percent of new infections occur, more than half affect women. In South Africa, for example, nearly 30 percent of all pregnant women are HIV-positive (South African Department of Health, 2009 ). Untreated HIV-infected expectant mothers pass the deadly virus to the developing organism 20 to 30 percent of the time.

TABLE 3.2 Effects of Some Infectious Diseases During Pregnancy

DISEASE

MISCARRIAGE

PHYSICAL MALFORMATIONS

MENTAL RETARDATION

LOW BIRTH WEIGHT AND PREMATURITY

VIRAL

Acquired immune deficiency syndrome (AIDS)

✗

?

✓

?

Chickenpox

✗

✓

✓

✓

Cytomegalovirus

✓

✓

✓

✓

Herpes simplex 2 (genital herpes)

✓

✓

✓

✓

Mumps

✓

?

✗

✗

Rubella (German measles)

✓

✓

✓

✓

BACTERIAL

Chlamydia

✓

?

✗

✓

Syphilis

✓

✓

✓

?

Tuberculosis

✓

?

✓

✓

PARASITIC

Malaria

✓

✗

✗

✓

Toxoplasmosis

✓

✓

✓

✓

✓ = established finding, ✗ = no present evidence, ? = possible effect that is not clearly established.

Sources: Jones, Lopez, & Wilson, 2003; Kliegman et al., 2008; Mardh, 2002; O’Rahilly & Müller, 2001.

AIDS progresses rapidly in infants. By 6 months, weight loss, diarrhea, and repeated respiratory illnesses are common. The virus also causes brain damage, as indicated by seizures, gradual loss in brain weight, and delayed mental and motor development. Nearly half of prenatal AIDS babies die by 1 year of age and 90 percent by age 3 (Devi et al., 2009 ). Antiretroviral drug therapy reduces prenatal AIDS transmission by as much as 95 percent, with no harmful consequences of drug treatment for children. These medications have led to a dramatic decline in prenatally acquired AIDS in Western nations. Although distribution is increasing, antiretroviral drugs are still not widely available in impoverished regions of the world (UNICEF, 2010a ).

As Table 3.2 reveals, the developing organism is especially sensitive to the family of herpes viruses, for which no vaccine or treatment exists. Among these, cytomegalovirus (the most frequent prenatal infection, transmitted through respiratory or sexual contact) and herpes simplex 2 (which is sexually transmitted) are especially dangerous. In both, the virus invades the mother’s genital tract, infecting babies either during pregnancy or at birth.

Babies are tested for the HIV virus in a clinic in Mozambique, Africa. Prenatal treatment with antiretroviral drugs reduces transmission of AIDS from mother to child by as much as 95 percent.

Bacterial and Parasitic Diseases.

Table 3.2 also includes several bacterial and parasitic diseases. Among the most common is toxoplasmosis, caused by a parasite found in many animals. Pregnant women may become infected from eating raw or undercooked meat or from contact with the feces of infected cats. About 40 percent of women who have the disease transmit it to the developing organism. If it strikes during the first trimester, it is likely to cause eye and brain damage. Later infection is linked to mild visual and cognitive impairments (Jones, Lopez, & Wilson, 2003 ). Expectant mothers can avoid toxoplasmosis by making sure that the meat they eat is well-cooked, having pet cats checked for the disease, and turning over the care of litter boxes to other family members.

Other Maternal Factors

Besides avoiding teratogens, expectant parents can support the development of the embryo and fetus in other ways. In healthy, physically fit women, regular moderate exercise, such as walking, swimming, biking, or an aerobic workout, is related to increased birth weight (Olson et al., 2009 ). However, frequent, vigorous exercise, especially late in pregnancy, results in lower birth weight than in healthy, nonexercising controls (Clapp et al., 2002 ; Leet & Flick, 2003 ). Most women, however, do not engage in sufficient moderate exercise during pregnancy to promote their own and their baby’s health (Poudevigne & O’Connor, 2006 ). An expectant mother who remains fit experiences fewer physical discomforts in the final weeks.

In the following sections, we examine other maternal factors—nutrition, emotional stress, blood type, age, and previous births.

Nutrition.

During the prenatal period, when children are growing more rapidly than at any other time, they depend totally on the mother for nutrients. A healthy diet that results in a weight gain of 25 to 30 pounds (10 to 13.5 kilograms) helps ensure the health of mother and baby.

Prenatal malnutrition can cause serious damage to the central nervous system. The poorer the mother’s diet, the greater the loss in brain weight, especially if malnutrition occurred during the last trimester. During that time, the brain is increasing rapidly in size, and a maternal diet high in all the basic nutrients is necessary for it to reach its full potential. An inadequate diet during pregnancy can also distort the structure of the liver, kidney, pancreas, and other organs, resulting in lifelong health problems, including cardiovascular disease and diabetes in adulthood (Barker, 2008 ; Whincup et al., 2008 ).