Pregnancy

• Introduction
• Physical factors
• Nutrient needs
• Dietary choices
• References

The most pertinent nutrition message for pregnant women can be summarized in one word: EAT! During pregnancy, more than at any other time in a woman’s life, it is vitally important to eat lots of healthy food.

Although women throughout history seem to have unwittingly recognized the importance of eating a healthy diet during pregnancy, the first scientific studies on the relationship between maternal diet and pregnancy outcomes did not begin until the 1930’s.

These studies were initiated after it was observed that severe food shortages in many parts of Europe during World War I resulted in a tremendous increase in the number of miscarriages, stillbirths, infant deaths and birth defects in Europe.

It is now a well-known scientific fact that the nutritional status of the pregnant woman affects the outcome of the pregnancy, especially related to birth weight. Low birth weight is associated with an increased risk for infant deaths and developmental disabilities, and is seen more often in children from undernourished and underweight mothers.

During a healthy pregnancy, the body undergoes many changes to allow for the growth of the fetus and to prepare the mother for labor, delivery and lactation. Many of these changes increase the nutritional requirements of the mother.

To ensure that nutritional needs are met, pregnant women are encouraged to consume a diet rich in vegetables, fruits, and whole grains, and to take a daily vitamin and mineral supplement to guarantee adequate intake of iron and folic acid.

During the course of a normal pregnancy, the mother-to-be experiences physiologic changes that affect nearly every function of the body. These changes are necessary to support the growth of the fetus and to prepare the mother for labor, delivery and lactation. As these changes occur, the nutrient needs of the mother increase.

Pregnancy is accompanied by a 50% increase in maternal blood volume. To produce the additional blood needed to support the growth of the fetus, the body needs extra fluid, iron and vitamin B12. Due to the increase in blood volume, the kidneys do not work as efficiently during pregnancy. As a result, many nutrients that the kidney would normally reabsorb, especially glucose, amino acids and water-soluble vitamins, are lost in the urine. Inefficient kidney function also makes it difficult for the body to remove excess water, which results in swelling in the ankles.

Maternal weight gain is a necessary physiologic change of pregnancy. Interestingly, the fetus, placenta, and amniotic fluid account for less than half of the total amount of weight gained. Most of the added weight is found in maternal reproductive tissues, fluid and blood, and maternal fat stores, which serve as an energy reserve during pregnancy and lactation.

For women who fall within a normal prepregnancy weight range, a 25 to 35 pound weight gain is healthy. Women who start pregnancy underweight usually need to gain 28 to 40 pounds, which may require caloric intake above that typically recommended during pregnancy. Overweight women are often encouraged to gain between 15 and 25 pounds.

To support the growth and development of the fetus, a pregnant woman requires extra amounts of nearly all essential nutrients. In fact, the recommended intake of some of the nutrients, including iron and folic acid, increases so much over nonpregnancy amounts that most physicians encourage pregnant women to take a vitamin and mineral supplement each day to ensure nutrient needs are met.

In addition to maximizing nutrient intake, the mother-to-be is also encouraged to completely avoid alcohol and limit intake of caffeine to no more than 200 mg/day, the equivalent of 2 cups of coffee.

The Dietary Reference Intakes for pregnant and nonpregnant women appear in the table below. The nutrients highlighted below are of special importance:

• Calories: Additional calories are required during pregnancy. It has been estimated that it takes 75,000 to 80,000 calories to make a baby, which represents approximately 2400 to 2600 calories per day throughout the pregnancy. Food and caloric intake must be high enough to ensure that all nutritional needs are met, and to allow for a 14-ounce weight gain per week during the last 30 weeks of pregnancy.

  Nevertheless, daily calorie needs are highly individual, and will vary depending on the woman’s prepregnancy weight (was she underweight or overweight at the beginning of her pregnancy?), the level and type of exercise the woman participates in, and her rate of weight gain throughout the pregnancy.

• Protein: Extra protein is needed during pregnancy to help with the synthesis of maternal and fetal tissue. The most current recommendations for protein requirements during pregnancy made by the Institute of Medicine, which establishes government guidelines for protein requirements, were established in 1989. The Institute of Medicine recommends 60 grams of protein per day during pregnancy.

• Fat: The recommendations for the amount of fat as a percentage of total calories do not change during pregnancy, so like all adults, pregnant women should consume no more than 30% of calories as fat. However, the type and quality of fat eaten during pregnancy is especially important. Mothers-to-be are encouraged to increase their consumption of the foods containing omega 3 fats, as the omega 3 fat docosahexaenoic acid (DHA) is necessary for the development of brain and nerve tissue in the fetus.

• Folic acid: In recent years, the need for extra folic acid before and during pregnancy has been widely publicized, as researchers continue to establish a connection between the neural tube defects and folic acid deficiency. Neural tube defects, such as spina bifida, are among the most common birth defects in the United States, with approximately 2500 new cases occurring the each year.

• Vitamin B12: Additional vitamin B12 is needed for synthesis of red blood cells.

• Thiamin, riboflavin, and niacin: These B vitamins participate in the production of energy throughout the body, which is especially important during pregnancy.

• Vitamin B6: This vitamin is required for protein synthesis. In addition, vitamin B6 may help reduce severe nausea and vomiting, and may also help prevent depression during pregnancy.

• Iron: Iron is needed to produce hemoglobin, the oxygen-carrying molecule found in red blood cells. Because the maternal blood supply increases during pregnancy, the body’s need for iron also increases. In many circumstances, the need for iron is not met from food sources alone, and supplementation is required to prevent iron-deficiency anemia.

• Zinc: Zinc participates in many physiological functions as a constituent of several enzymes, and zinc deficiency is known to cause birth defects in animals.

• Magnesium: Extra magnesium is needed to support fetal and maternal tissue growth.

• Iodine: Iodine deficiency during pregnancy is associated with cretinism, a congenital condition characterized by lack of thyroid hormone. Cretinism can cause physical and developmental delays.

• Vitamin A: It is important to note that the requirement of vitamin A does not increase during pregnancy. Vitamin A can be toxic to the fetus when consumed by the mother in amounts greater than 7500 RE per day. Pregnant women should not take supplements of vitamin A that exceed the Dietary Reference Intake, and should avoid all prescription and OTC drugs used in the treatment of acne that made from vitamin A analogs, such as isotretinoin.

• Calcium: Although the requirement for calcium does not increase during pregnancy, it is important that pregnant women ensure adequate intake of this mineral. High dietary intake of calcium is needed for skeletal development of the fetus and to preserve maternal calcium stores. Additionally, calcium may also help prevent hypertension, a dangerous pregnancy complication.

• Water: While not exactly a nutrient, water is definitely essential for a healthy pregnancy. Due to the increase in blood volume during pregnancy, fluid needs increase dramatically. In addition, extra fluid intake can help prevent constipation, a common problem during pregnancy.

It is common for pregnant women to experience fluctuations in appetite and food intake due to hormonal changes and changes in the gastrointestinal tract as the fetus develops. Several of the factors that affect dietary choices during pregnancy are listed below:

• During the first trimester and sometimes extending into later months of pregnancy, women suffer from morning sickness. Nausea and vomiting may decrease appetite and limit food intake. In addition, excessive vomiting may cause loss of minerals and vitamins, and lead to dehydration. Some women find that eating small, frequent meals helps them get some food down despite the nausea.

• Many pregnant women experience intense food cravings and food aversions. In addition, the sense of taste and smell is frequently altered during pregnancy. These changes can lead to excessive consumption of certain foods or food groups, and insufficient consumption of other foods.

  However, this is typically a concern only if the foods that are frequently consumed contain lots of calories and fat and few vitamins and minerals, or if the woman is unable or unwilling to eat any fruits or vegetables due to food aversions or altered taste.

• Constipation is a common occurrence during pregnancy, resulting from a variety of factors including pressure exerted on the intestines by the enlarged uterus, mineral supplements, and/or decreased physical activity. Constipation is not only uncomfortable, but it also leads to reduced appetite and food intake, which can have nutritional consequences.

  To prevent constipation, pregnant women are encouraged to increase their fluid intake and their consumption of fiber-rich foods such as fruits, vegetables and whole grains.

• As the womb grows, the size of the stomach shrinks, causing the mother-to-be to fill up faster. In addition, the valve between the esophagus and the stomach relaxes, which can cause heart burn and/or acid reflux. In the later months of pregnancy, many women find it more comfortable and enjoyable to eat small, frequent meals throughout the day. Remaining upright after meals helps prevent heartburn.

• Many women choose to follow a vegetarian diet during pregnancy. Although it is possible to obtain sufficient amounts of all nutrients from a vegetarian diet, pregnant women following a vegetarian or vegan diet should take extra care to ensure adequate intake of iron, calcium, vitamin D, zinc, and vitamin B12.

• Certain diseases and/or medical conditions impact the dietary choices of pregnant women. For example, a pregnant woman with adult onset diabetes or gestational diabetes must pay special attention to the type of food she eats and the timing of meals to maintain blood sugar levels within a normal range.

• . Longitudinal studies of diet in pregnancy. Nutr Rev 1972 Feb;30(2):38-40. 1972.

• Anderson A. Diet and pregnancy: what to advise. Practitioner 1994 Sep;238(1542):607-11. 1994.

• Antal M. [Current questions concerning nutrition during pregnancy]. Orv Hetil 1999 Nov 7;140(45):2507-11. 1999. PMID:18830.

• Chopra A. Ayurvedic medicine and arthritis. Rheum Dis Clin North Am 2000 Feb;26(1):133-44, x. 2000.

• Doyle W. Nutrition and pregnancy. Nurs Times 1998 Apr 22-1998 Apr 28;94(16):Suppl 1-6. 1998. PMID:18840.

• Ladipo OA. Nutrition in pregnancy: mineral and vitamin supplements. Am J Clin Nutr 2000 Jul;72(1 Suppl):280S-90S. 2000. PMID:18820.

• Mahan LK, Stump S. Krause’s Food Nutrition and Diet Therapy 10th Ed. WB Saunders Co 2000. 2000.

• Oldak E. [Maternal elimination diet during pregnancy and lactation, and the development of allergies in infants]. Pol Merkuriusz Lek 1998 Dec;5(30):387-9. 1998. PMID:18760.

• Pearson S. Nutrition in pregnancy. Nurs Times 1998 Apr 8-1998 Apr 14;94(14):52-3. 1998. PMID:18850.

• Romon M. [Does diet sufficiently cover the needs of pregnancy?]. J Gynecol Obstet Biol Reprod (Paris) 1997;26 Suppl 3:55-8. 1997.

• Scholl TO, Johnson WG. Folic acid: influence on the outcome of pregnancy. Am J Clin Nutr 2000 May;71(5 Suppl):1295S-303S. 2000. PMID:10430.

• Udipi SA, Ghugre P, Antony U. Nutrition in pregnancy and lactation. J Indian Med Assoc 2000 Sep;98(9):548-57. 2000. PMID:18810.

• Weigel MM, Narvaez WM, Lopez A, et al. Prenatal diet, nutrient intake and pregnancy outcome in urban Ecuadorian primiparas. Arch Latinoam Nutr 1991 Mar;41(1):21-37. 1991.

• Worthington-Roberts B, Williams S. Nutrition in Pregnancy and Lactation, Fifth Edition. Mosby: St. Louis, 1993. 1993.

References

1. . Longitudinal studies of diet in pregnancy. Nutr Rev 1972 Feb;30(2):38-40. 1972.
2. Anderson A. Diet and pregnancy: what to advise. Practitioner 1994 Sep;238(1542):607-11. 1994.
3. Antal M. [Current questions concerning nutrition during pregnancy]. Orv Hetil 1999 Nov 7;140(45):2507-11. 1999. PMID:18830.
4. Chopra A. Ayurvedic medicine and arthritis. Rheum Dis Clin North Am 2000 Feb;26(1):133-44, x. 2000.
5. Doyle W. Nutrition and pregnancy. Nurs Times 1998 Apr 22-1998 Apr 28;94(16):Suppl 1-6. 1998. PMID:18840.
6. Ladipo OA. Nutrition in pregnancy: mineral and vitamin supplements. Am J Clin Nutr 2000 Jul;72(1 Suppl):280S-90S. 2000. PMID:18820.
7. Mahan LK, Stump S. Krause's Food Nutrition and Diet Therapy 10th Ed. WB Saunders Co 2000. 2000.
8. Oldak E. [Maternal elimination diet during pregnancy and lactation, and the development of allergies in infants]. Pol Merkuriusz Lek 1998 Dec;5(30):387-9. 1998. PMID:18760.
9. Pearson S. Nutrition in pregnancy. Nurs Times 1998 Apr 8-1998 Apr 14;94(14):52-3. 1998. PMID:18850.
10. Romon M. [Does diet sufficiently cover the needs of pregnancy?]. J Gynecol Obstet Biol Reprod (Paris) 1997;26 Suppl 3:55-8. 1997.
11. Scholl TO, Johnson WG. Folic acid: influence on the outcome of pregnancy. Am J Clin Nutr 2000 May;71(5 Suppl):1295S-303S. 2000. PMID:10430.
12. Udipi SA, Ghugre P, Antony U. Nutrition in pregnancy and lactation. J Indian Med Assoc 2000 Sep;98(9):548-57. 2000. PMID:18810.
13. Weigel MM, Narvaez WM, Lopez A, et al. Prenatal diet, nutrient intake and pregnancy outcome in urban Ecuadorian primiparas. Arch Latinoam Nutr 1991 Mar;41(1):21-37. 1991.
14. Worthington-Roberts B, Williams S. Nutrition in Pregnancy and Lactation, Fifth Edition. Mosby: St. Louis, 1993. 1993.