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NUTRITION FOR PREGNANCY, BREASTFEEDING, AND INFANCY

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Few sights are more distressing to a midwife than that of an unresponsive newborn. But this was the situation Judith Mercer, a certified nurse-midwife, was facing when she assisted in a home birth in 1979. As she stared at the pale and lifeless little boy, she was terrified that she wouldn’t be able to resuscitate him. She tried to stimulate him with her fingers and he did not respond. She looked down at the umbilical cord, which connected the baby directly to his mother’s placenta, and saw that it was pulsating—still delivering blood to the boy’s body. His color was ever-so-slowly returning. A minute-and-a-half later, the little boy opened his eyes and took a quiet breath. He did not even cry. The still-attached umbilical cord, Mercer realized, had seemingly saved this boy’s life by pumping blood and oxygen—life, basically—from his mother’s body to his own.

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Mercer was awed by what she had seen. She vowed, right then and there, to study what she had witnessed and understand why and how the umbilical cord might have saved that baby boy. “That baby affected the whole second half of my lifetime,” she says. Mercer went back to school, got a PhD, and as a clinical professor of nursing at the University of Rhode Island, she has dedicated her life to studying the benefits of what is known as delayed cord clamping. Usually, within seconds of a birth, obstetrical care providers clamp the umbilical cord connecting mother to baby, severing the blood flow between them. As Mercer’s research has shown, however, delaying the clamping of the umbilical cord by several minutes can provide benefits. Not only does the cord continue to provide blood and oxygen to the newborn in the event of a trauma, but it also increases the baby’s stores of iron—crucial for the development of certain types of brain cells—yet a nutrient in that some babies may become deficient of, as breast milk is not naturally rich in iron.

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In March 2013, the Cochrane Collaboration, a nonprofit international consortium funded in part by the U.S. Department of Health and Human Services, analyzed the results of 15 clinical trials—many conducted by Mercer—and concluded that delayed clamping increases birth weight (by increasing the newborn’s blood volume) and halves the risk that babies will be iron-deficient when they are three or six months old. (Iron deficiency is a risk factor for future cognitive problems.) Yet few healthcare providers who deliver babies today delay the clamping of umbilical cords, in part because it takes extra time and in part because delaying clamping slightly increases the risk for newborn jaundice, a condition that arises when a baby’s liver has trouble processing a byproduct of red blood cell breakdown called bilirubin so that it can be excreted. Jaundice, however, can usually be treated with ultraviolet light therapy in the hospital and rarely causes complications. Ultimately, Mercer hopes that with additional research—she is now starting a clinical trial to see whether delayed cord clamping improves scores on developmental tests at age two years—she can prove that the practice is both safe and beneficial.

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Although Mercer’s research points to the importance of the umbilical cord after birth, its primary purpose is to supply nutrients and oxygen to a developing baby during pregnancy, the period from fertilization to birth. Pregnancy begins when a woman’s egg is fertilized by a sperm, forming a zygote that develops into an embryo and then a fetus.

Starting about five weeks after fertilization, the umbilical cord develops and then supplies the fetus with nutrients and oxygen and removes waste until it is clamped after birth. The fetus is carried in a fluid-filled amniotic sac in the muscular organ known as the uterus. The umbilical cord connects the fetus to the placenta, which is attached to the uterus. (INFOGRAPHIC 17.1)

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Between two and eight weeks after fertilization, as the organs and vital systems begin to develop, a developing human is referred to as an embryo. At the tenth week of pregnancy (eight weeks after fertilization), the developing human is called a fetus, and its organs mature as it puts on significant amounts of weight (from less than one ounce to between about seven and eight pounds at birth).

The entire period of development from fertilization to birth is called gestation. Full-term pregnancies last between 38 and 42 weeks, and are, on average, about 40 weeks long, calculated from the first day of the woman’s last menstrual period. Pregnancy is split into three periods called trimesters: weeks 1 to 13 are considered the first trimester; weeks 14 to 27 compose the second trimester; and weeks 28 to 40 make up the third trimester. (INFOGRAPHIC 17.2)