Articles

Nutrition in Pregnancy

November 9, 2019


My name is Dr. Jan Eperjesi. I’m a resident in obstetrics and gynecology at Duke University. This presentation is about nutrition in pregnancy. For this presentation on nutrition and pregnancy, there are four learning objectives. Number one is to learn the recommendations for weight gain in pregnancy. Number two is to appreciate maternal and fetal risks associated with excessive or inadequate weight gain in pregnancy. Number three is to appreciate typical weight loss after pregnancy. Number four is to provide information about caloric intake, protein sources, mercury toxicity from certain fish, iron requirements, folic acid, vitamin A, calcium, caffeine, and pica. This chart shows the recommended weight gain in pregnancy for different body mass indexes. In 1990, the Institute of Medicine recommended a weight gain of 25 to 35 pounds or 11.5 to 16 kilograms for women with a normal pre-pregnancy body mass index. The range for twin pregnancy is 35 to 45 pounds or 16 to 20 kilograms. Young adolescents that have had less than two periods after their first menses should strive for gains at the upper end of this range. Shorter women, meaning women less than 62 inches or 157 centimeters in height, should strive for gains at the lower end of this range. For a body mass index less than 19.8, a greater overall weight gain is recommended. For higher BMIs, the recommended weight gain is between 15 to 25 pounds or seven to 11.5 kilograms. The current recommendations for adequate weight gain are from the Institute of Medicine in 1990. The rationale for these recommendations aims to prevent pre-term birth and fetal growth restriction, which are associated with inadequate weight gain. Interestingly, however, the current focus is on the obesity epidemic. Obesity is associated with significantly increased risk for gestational hypertension, preeclampsia, gestational diabetes, macrosommia, and cesarean delivery. Studies have shown that in obese pregnant women, those who gained less than 15 pounds had the lowest rates of pre-eclampsia, large for gestational age infants, and cesarean delivery. Other studies have shown that women with normal pre-pregnancy body mass indexes who gain less than 25 pounds during pregnancy, also had a lower risk for pre-eclampsia, failed induction, cephalopelvic disproportion, cesarean delivery, and large for gestational age infants. Most, but not all, of the weight gain during pregnancy is lost during and immediately after delivery. In women whose average weight gain is 29 pounds during pregnancy, approximately 12 pounds is lost at delivery. In the next two weeks after delivery, there is an additional nine pounds of weight loss. A further six pounds is then lost between two weeks and six months postpartum. Overall, the more weight gain during pregnancy, the more that is lost post-partum. Interestingly, however, there is no relationship between pre-pregnancy body mass index or prenatal weight gain and weight retention. To the basic protein needs of the non-pregnant woman are the added demands for growth and remodeling of the fetus, placenta, uterus, and breasts, as well as increased blood volume. During the second half of pregnancy, approximately 1,000 grams of protein are deposited amounting to five to sic grams per day. The concentrations of most amino acids in maternal plasma fall markedly. Preferably, most protein should be supplied from animal sources such as meat, milk, eggs, cheese, poultry, and fish because they provide amino acids in optimal combinations. Milk and dairy products have long been considered nearly ideal sources of nutrients, especially protein and calcium, for pregnant or lactating women. Fish are an excellent source of protein, are low in saturated fats, and contain omega 3 fatty acids. Because nearly all fish and shellfish contain trace amounts of mercury, pregnant and lactating women are advised to avoid specific types of fish with potentially high methyl mercury levels. These include shark, swordfish, King mackerel, and tile fish. It is further recommended that pregnant women ingest no more than 12 ounces or two servings of canned tuna per week. And no more than six ounces of albacore or white tuna. If the mercury content of locally caught fish is unknown, then overall fish consumption should be limited to six ounces per week. With respect to folic acid, greater than 50% of all neural-tube defects can be prevented with daily intake of 400 micrograms of folic acid throughout the pre-conceptual period. The Center for Disease Control in 2004 estimated that the number of pregnancies effected by neural tube defects has decreased from 4,000 pregnancies per year to approximately 3,000 per year since mandatory fortification of cereal products with folic acid in 1998. By adding 140 micrograms to folic acid to each 100 grams of grain products, the intake of folic acid by women of childbearing age may be increased by 100 micrograms per day. However, because nutritional sources alone are insufficient, folic acid supplementation is still recommended. For those women with a prior child with a neural-tube effect, the recurrence risk, which is approximately 2% to 5%, can be reduced by more than 70% with daily folic acid supplements of four milligrams per day in the month before conception and during the first trimester. Note the difference between 400 micrograms for women with no prior history of a neural-tube defect versus four milligrams if there is a history of a neural-tube defects. With the exception of iron, practically all diets that supply sufficient calories for appropriate weight gain will contain enough materials to prevent deficiency if iodized foods are ingested. 300 milligrams of iron is transferred to the fetus and placenta. 500 milligrams is incorporated into the expanding maternal hemoglobin mass. Nearly all is used after mid-pregnancy. The pregnant woman may benefit from 60 to 100 milligrams of iron per day if she is large, has twin fetuses, begins supplementation late in pregnancy, takes iron irregularly, or has depressed hemoglobin levels. With respect to calcium, most maternal calcium is in bone and can be readily mobilized for fetal growth. There is also increased calcium absorption by the intestine and progressive retention throughout pregnancy. Vitamin A is associated with birth defects at very high doses in the range of 10,000 to 50,000 international units daily. There is no vitamin A toxicity, however, with a beta carotene precursor of vitamin A that is found in fruits and vegetables. The American College of Obstetricians and Gynecologists does not recommend supplementation of vitamin A because intake in the United States is adequate. However, in developing countries, vitamin A deficiency is an endemic nutrition problem. It causes night blindness in pregnant women and is associated with increased risk of anemia and pre-term birth. It is estimated six 6 million pregnant women suffer from night blindness, secondary to vitamin A deficiency. The American Dietetic Association recommends that caffeine intake in pregnancy be limited to less than 300 milligrams per day or about three five ounce cups of coffee. However, only extremely high levels of caffeine equivalent to greater than five cups of coffee per day, may have possible association with spontaneous abortion. Adverse outcomes related to caffeine are controversial. These include possible low birth weight, fetal growth restriction, and pre-term delivery. One study showed that if greater than 200 milligrams of caffeine throughout pregnancy was consumed, there was an increased odds ratio of 1.4 for fetal growth restriction. Pica is defined as craving of pregnant women for strange foods, such as starch and sourdough or non-food items, for example, ice, starch, or clay. There is a 4% prevalence of pica in the second trimester. Pica may be triggered by severe iron deficiency, but the corollary statement is not necessarily true. All women with pica are not necessarily iron deficient. Interestingly, pre-term delivery at less than 35 weeks is twice as high in women with pica.

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