Prenatal nutrition

Definition

Maternal nutrition during pregnancy affects both the health of the mother and the growing fetus. Requirements for calories and specific nutrients are increased for the baby's growth and proper development. These needs can be met by increasing healthful food consumption and specific nutrient supplementation.

Purpose

Proper prenatal nutrition helps ensure a healthy start for a new baby and promotes the mother's well-being during and after pregnancy. Nurses and other allied health professionals can play a role in educating pregnant women about sufficient weight gain, the importance of a healthy diet, and the following recommendations for supplementation.

Precautions

Maternal weight gain during pregnancy is an important predictor of a baby's birth weight. The height and weight of the mother before pregnancy should be taken into account when assessing maternal nutrient needs. Both underweight and excessively overweight women need special attention. Underweight women are more likely to give birth to premature or low birth-weight infants, while overweight women have an increased risk of developing pregnancy-related complications. Other high-risk groups for low birth-weight babies include women younger than 15 and those older than 35. Women whose pregnancies are fewer than 12 months apart are also at higher risk.

Description

Maternal weight gain is a measure often used to assess how well a pregnancy is progressing. Normal weight gain is considered to be 25 to 35 pounds, although individual needs should also be taken into account. Women who are underweight to start with may benefit from gaining more (28-40 pounds), while overweight women may try to gain less (15-25 pounds). Even for overweight women, however, weight gain is important to allow for proper growth of the fetus.

Nutrient needs during pregnancy depend on physical activity and metabolism of the mother. For most women, energy needs increase to about 300 extra calories per day during the second and third trimesters. Protein needs increase to allow for new tissue growth and maintenance; deficiency can result in lower a birth weight. An extra 10 to 12 grams of protein per day is recommended during the last half of pregnancy.

Vitamin and mineral requirements are also increased during pregnancy. To meet those needs, most women in the United States are advised to take a multivitamin supplement with minerals while they are pregnant. Eating a well-balanced diet with plenty of fruits, vegetables, and whole grains will also help provide the needed vitamins . Iron and calcium are two minerals of special concern. The fetus acquires most of these minerals during the last trimester of the pregnancy. Doctors recommend daily supplementation of 30 mg of iron in the form of ferrous sulfate to avoid iron deficiency anemia , which can cause excessive tiredness in the mother. Calcium intake should be 1,200 to 1,500 mg per day, which can be obtained through diet or supplementation. Adequate calcium is important so that the mother does not lose bone mass during pregnancy. There is also some evidence that calcium supplementation reduces the risk of pregnancyinduced hypertension , also known as preeclampsia, for women who are at high risk for this condition.

Folate (folic acid ) is an extremely important vitamin, not only during pregnancy, but before pregnancy as well. Folate is crucial to the development of new cells, and deficiency during pregnancy has been associated with the development of congenital malformations known as neural tube defects (NTDs). The most serious NTDs include spina bifida and anencephaly. Spina bifida is characterized by gaps in the spine, typically resulting in serious lifelong disability. An infant with anencephaly lacks brain formation and dies shortly after birth. Because NTDs arise early in pregnancy, before most women know they are pregnant, the U.S. Public Health Service recommends that all women of childbearing age consume 0.4 mg (400 micrograms) of folic acid daily. Adequate amounts of folate can be obtained from the diet, but in practice most women do not consume enough. To help address this problem, in 1996 the U.S. Food and Drug Administration (FDA) approved folate fortification of flour, breads, cereal, and rice.

Complications

Good nutrition is especially important for certain conditions during pregnancy. Diabetes, a disease of poor blood sugar regulation, is one common problem requiring special attention to diet. Some women develop it only during pregnancy, when it is termed gestational diabetes . It can lead to multiple complications, including abnormally enhanced growth of the fetus, a condition called macrosomia. Such babies need special care at birth until blood sugar levels can be brought under control. Control of gestational diabetes includes careful attention to diet so that maternal blood sugar levels are kept as normal as possible throughout pregnancy. Women should eat frequent small meals; select foods high in fiber and complex carbohydrates ; and avoid highly refined foods and simple sugars.

Another common problem is nausea and vomiting in early pregnancy. Because hunger seems to exacerbate the problem, suggestions to alleviate nausea include eating small, frequent meals of easily digestible foods, and having dry crackers near the bed to eat immediately upon awakening. Some women have severe enough symptoms that they are in danger of weight loss, dehydration , and electrolyte disturbances. This condition, termed hyperemesis gravidarum, may require hospitalization or medications to treat it if simple nutritional measures cannot control it.

Phenylketonuria (PKU) is a more unusual condition, but it is one in which the importance of maternal nutrition is paramount. PKU and the related condition, hyperphenylalanemia (HPA), are genetic disorders involving the impairment of the ability to digest phenylalanine, an essential amino acid found in protein. Before the disease was recognized, people with PKU developed severe mental retardation in childhood. Since routine screening and early dietary treatment has been instituted, people with PKU now can develop normally. However, women with these conditions may be advised not to become pregnant because of the high risk of mental retardation and congenital defects in the developing fetus. Women who desire pregnancy should discuss their plans with health personnel in a clinic that specializes in the treatment of these disorders well before becoming pregnant, so that strict dietary measures can be taken before conception and throughout pregnancy.

An abnormal food behavior that sometimes occurs in pregnant women is pica, which involves the consumption of such nonfood items as cornstarch, dirt, hair, cigarette ashes, or coffee grounds. Pica is sometimes associated with iron deficiency; and some think that the consumption of these substances may relieve the nausea and vomiting associated with pregnancy. Although many of these

KEY TERMS

Congenital malformations —Deformities that occur at birth.

Gestational diabetes —A disorder occurring in pregnancy involving insensitivity to insulin, causing poor blood sugar regulation.

Hyperemesis gravidarum —Excessive vomiting during pregnancy.

Macrosomia —An abnormally large body. Macrosomia of the newborn is a common complication of gestational diabetes.

Phenylketonuria (PKU) —A congenital deficiency of an enzyme that aids in the breakdown of an amino acid, leading to the development of severe mental retardation. PKU can be controlled with a strict diet, which is especially critical during pregnancy of a mother with PKU to avoid physical and mental defects in the fetus.

Pica —A desire that sometimes arises in pregnancy to eat such non-food substances as dirt or clay.

Preeclampsia —A syndrome of high blood pressure that develops during pregnancy. The chief danger of preeclampsia is that it will progress to eclampsia, which is a life-threatening condition characterized by seizures.

substances are not inherently harmful, there is a concern that such habits may displace the intake of nutritious foods during pregnancy.

Alcohol consumption during pregnancy can result in fetal alcohol syndrome (FAS), characterized by varying degrees of numerous physical and mental problems, including mental retardation, facial abnormalities, and heart and skeletal defects. Because of the unpredictable effects of even small amounts of alcohol, women are advised to drink no alcohol at any time during pregnancy.

Quitting smoking and avoiding secondhand smoke is especially important during pregnancy. Exposure to tobacco smoke increases the risk of a low birth-weight infant.

The effect of food additives is controversial, but doctors recommend that sugar substitutes, including saccharin and aspartame, be used in moderation if at all. Caffeine consumption during pregnancy is another debatable issue, although too much caffeine may have negative effects.

Especially for teenagers and young women, eating disorders may be of concern. Anorexia, bulimia nervosa (characterized by episodes of binge eating and vomiting), use of laxatives , or excessive exercising pose a serious risk to the mother and the fetus. Poor weight gain during pregnancy may indicate the presence of a eating disorder.

Results

Good nutrition and adequate weight gain in pregnancy increase the likelihood that the mother will feel herbest during pregnancy and that a healthy baby will beborn with a normal birth weight. Specific nutrient deficiencies can lead to birth defects, as is well documented for folic acid; or health consequences to the mother (e.g., calcium deficiency's possible role in preeclampsia). Inaddition, nutritional intervention is the treatment ofchoice for several conditions, including gestational diabetes, nausea and vomiting in pregnancy, and maternal PKU.

Health care team roles

Dietetic professionals, nurse practitioners, nursemidwives, and physicians play an important role in the prenatal care of pregnant women. Dietitians can provide the nutrition counseling and education necessary toensure the normal growth and development of the fetus. They can warn women about the dangers of improperfood intake and the outcome it may have on pregnancy. Physicians are primarily responsible for determining thatthe fetus is growing properly and for detecting and monitoring medical conditions. In uncomplicated pregnancies, nurse practitioners and nurse midwives may play amore prominent role in prenatal care.

Resources

BOOKS

Worthington-Roberts, Bonnie S., and Sue Rodwell Williams. Nutrition Throughout the Life Cycle, 4th Edition. Boston, MA: McGraw-Hill Companies, Inc., 2000.

PERIODICALS

Morrill, Elizabeth S. and Haron M. Nickols-Richardson."Bulimia Nervosa During Pregnancy: A Review."Journal of the American Dietetic Association (April 2001): 448-454.

Lisa M. Gourley