Lifespan Development. Tara L. Kuther

reflex). By the end of the 12th week, the upper limbs have almost reached their final relative lengths, but the lower limbs are slightly shorter than their final relative lengths (Sadler, 2015).

      Second Trimester (14 to 26 Weeks)

      By the 14th week, at the start of the second trimester, limb movements are coordinated, but they will be too slight to be felt by the mother until about 17 to 20 weeks. The heartbeat gets stronger. Eyelids, eyebrows, fingernails, toenails, and tooth buds form. The first hair to appear is lanugo, a fine down-like hair that covers the fetus’s body; it is gradually replaced by human hair. The skin is covered with a greasy material called the vernix caseosa, which protects the fetal skin from abrasions, chapping, and hardening that can occur with exposure to amniotic fluid (K. L. Moore & Persaud, 2016). At 21 weeks, rapid eye movements begin, signifying an important time of growth and development for the fetal brain. The brain begins to become more responsive. For example, startle responses have been reported at 22 to 23 weeks in response to sudden vibrations and noises (Hepper, 2015). During weeks 21 to 25, the fetus gains substantial weight, and its body proportions become more like those of a newborn infant. Growth of the fetal body begins to catch up to the head, yet the head remains disproportionately larger than the body at birth.

      Third Trimester (27 to 40 Weeks; Seventh, Eighth, Ninth Months)

      During the last 3 months of pregnancy, the fetal body grows substantially in weight and length; specifically, it typically gains over 5 pounds and grows 7 inches. At about 28 weeks after conception, brain development grows in leaps and bounds. The cerebral cortex develops convolutions and furrows, taking on the brain’s characteristic wrinkly appearance (Andescavage et al., 2016). The fetal brain wave pattern shifts to include occasional bursts of activity, similar to the sleep-wake cycles of newborns. By 30 weeks, the pupils of the eyes dilate in response to light. At 35 weeks, the fetus has a firm hand grasp and spontaneously orients itself toward light.

      During the third trimester, pregnant women and their caregivers are mindful that the baby may be born prematurely. Although the expected date of delivery is 266 days or 38 weeks from conception (40 weeks from the mother’s last menstrual period), about 1 in every 10 American births is premature (Centers for Disease Control and Prevention, 2017b). The age of viability—the age at which advanced medical care permits a preterm newborn to survive outside the womb—begins at about 22 weeks after conception (Sadler, 2015). Infants born before 22 weeks rarely survive more than a few days, because their brain and lungs have not begun to function. Although a 23-week fetus born prematurely may survive in intensive care, its immature respiratory system places it at risk; only about one third of infants born at 23 weeks’ gestation survive (Stoll et al., 2015). At about 26 weeks, the lungs become capable of breathing air and the premature infant stands a better chance of surviving if given intensive care. About 80% of infants born at 25 weeks survive, and 94% of those born at 27 weeks also survive. Premature birth has a variety of causes, including many environmental factors.

      Contextual and Cultural Influences on Prenatal Care

      Prenatal care, a set of services provided to improve pregnancy outcomes and engage the expectant mother, family members, and friends in health care decisions, is critical for the health of both mother and infant. About 26% of pregnant women in the United States do not seek prenatal care until after the first trimester; 6% seek prenatal care at the end of pregnancy or not at all (U.S. Department of Health and Human Services, 2014). Inadequate prenatal care is a risk factor for low-birthweight and preterm births as well as infant mortality during the first year (Partridge, Balayla, Holcroft, & Abenhaim, 2012). In addition, use of prenatal care predicts pediatric care throughout childhood, which serves as a foundation for health and development throughout the lifespan.

      A rural health care worker in India gives prenatal care to a pregnant woman. Birth practices vary by culture.

      S. Nagendra/Science Source

      Why do women delay or avoid seeking prenatal care? A common reason is the lack of health insurance (Maupin et al., 2004). Although government-sponsored health care is available for the poorest mothers, many low-income mothers do not qualify for care or lack information on how to take advantage of care that may be available. Figure 3.3 lists other barriers to seeking prenatal care, including difficulty in finding a doctor, lack of transportation, demands of caring for young children, ambivalence about the pregnancy, depression, lack of education about the importance of prenatal care, lack of social support, poor prior experiences in the health care system, and family crises (Daniels, Noe, & Mayberry, 2006; Heaman et al., 2015; Mazul, Salm-Ward, & Ngui, 2016).

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      Figure 3.3 Reasons for Delayed Prenatal Care Among Women, 2009–2010

      Source: U.S. Department of Health and Human Services et al., 2013.

      Moreover, there are significant ethnic and socioeconomic disparities in prenatal care. As shown in Figure 3.4, prenatal care is linked with maternal education. About 86% of women with a college degree obtain first-trimester care, compared with less than two thirds of women with less than a high school diploma (U.S. Department of Health and Human Services, 2014). In addition, women of color are disproportionately less likely to receive prenatal care during the first trimester and are more likely to receive care beginning in the third trimester or no care (see Figure 3.5). Native Hawaiian and Native American women are least likely to obtain prenatal care during the first trimester, followed by Hispanic, African American, Asian American, and White American women (Hamilton, Martin, Osterman, Driscoll, & Rossen, 2017). In the most extreme case, only about half of Native Hawaiian or other Pacific Islander women obtain first-trimester care, and one in five obtains late or no prenatal care. Ethnic differences are thought to be largely influenced by socioeconomic factors, as the ethnic groups least likely to seek early prenatal care are also the most economically disadvantaged members of society.

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      Figure 3.4 Timing of Prenatal Care Initiation, by Maternal Education, 2012

      Source: U.S. Department of Health and Human Services et al., 2015.

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      Figure 3.5 Prenatal Care Beginning in the First Trimester and Late or No Care, by Race and Ethnicity, in the United States, 2016

      Source: Hamilton et al., 2017.

      Although prenatal care predicts better birth outcomes, cultural factors also appear to protect some women and infants from the negative consequences of inadequate prenatal care. In a phenomenon termed the Latino paradox, Latina mothers, despite low rates of prenatal care, tend to experience low birthweight and mortality rates below national averages. These favorable birth outcomes are striking because of the strong and consistent association between socioeconomic status and birth outcomes and because Latinos as a group are among the most socioeconomically disadvantaged ethnic populations in the United States (McGlade, Saha, & Dahlstrom, 2004; Ruiz, Hamann, Mehl, & OConnor, 2016).

      Several factors are thought to account for the Latino paradox, including strong cultural support for maternity, healthy traditional dietary practices, and the norm of selfless devotion to the maternal role (known as marianismo) (Fracasso & Busch-Rossnagel,