There is an additional protein requirements for a pregnant woman to support the synthesis of maternal and fetal tisues, but the magnitude of this increase is uncertain. Protein requirement increases throughout gestation and is maximum during the third trimester.
Additional amount of carbohydrates are recommended to provide enough calories in the diet to prevent ketosis and maintain appropriate blood glucose during pregnancy.
Certain vitamins have particular significance for optimal pregnancy outcome. In some instances the provision of these specific vitamins may be met through diet, and for others a vitamin-mineral supplement is necessary.
Folic acid requirements increase during pregnancy in response to the demands of maternal erythropoiesis and fetal and placental growth. Folic acid deficiency is marked by a reduced rate of DNA synthesis and mitotic activity in individual cells. Megaloblastic anemia is the latest stage of folate deficiency and it may not present until the third trimester. Oral contraceptives and some antibiotics may cause folate insufficiency. Women who smoke, consume moderate to heavy alcohol are at risk for marginal folate status.
Vitamin B6 has been used to manage severe nausea and vomiting in pregnancy.
Vitamin A plays a role in gene expression for acrosin and plasminogen activators, which are important for spermatogenesis in rams. In human cord blood vitamin A concentrations correlated with birth weight, head circumference, length, and gestation duration. Women, who have high vitamin A in their diets, need to be closely evaluated.
Vitamin D has long been appreciated for its positive effects on calcium balance during pregnancy. This vitamin and its metabolites cross the placenta and appear in fetal blood in the same concentration as in maternal circulation. Maternal vitamin D deficiency is associated with neonatal hypocalcemia and hypoplasia of tooth enamel. Fetal bone mineralization may be affected by maternal vitamin D deficiency. Vitamin D blood concentrations are often low in infants born to vitamin D-deficient mothers, and vitamin D deficiency is increasingly recognized in dark-skinned women.
A marked increase in the maternal blood supply during pregnancy greatly increases the demand for iron. Iron supplementation in the form of ferrous salts is often necessary to prevent iron deficiency anemia. Maternal anemia occurs in pregnant woman who do not use iron supplements or who are anemic when they enter pregnancy. An anemic woman poorly tolerates hemorrhage with delivery, which subsequently increases cardiac stress. An anemic woman is also more prone to develop puerperal infection. Excessive amounts of iron should be avoided because it has been implicated in the pathogenesis of preeclampsia and gestational diabetes.
Restriction of dietary sodium of the use of diuretics in pregnant women with edema is not recommended. Sodium restriction can cause stress in the renin-angiotensin-aldosterone system and result in water intoxication. Moderation in the use of salt and other sodium-rich foods is appropriate for pregnant women and aggressive restriction is usually unwarranted in pregnancy, and consumption of sodium should remain above 2 to 3 g/day. Everyone should select iodized salt.
Careful choices are needed to include all the nutrients for pregnancy in the daily diet.