Pregnancy Health Article

Pregnancy

Nutrition during the preconception period, as well as throughout a pregnancy, has a major impact on pregnancy outcome. Among prepregnancy considerations, the prepregnancy Body Mass Index (BMI), folic acid status, and socioeconomic status are the most important.

Prepregnancy BMI is an important factor in predicting pregnancy outcome, since both low prepregnancy and high prepregnancy BMI are associated with an increased risk for a negative pregnancy outcome.

Folic acid, a B vitamin, has been shown to prevent birth defects of the brain and spinal cord known as neural tube defects (NTDs). The most common NTDs are spina bifida and anencephaly. Folic acid is therefore needed

both in preconception and early pregnancy. Since studies indicate that most women get less than half the recommended amount of folic acid, the March of Dimes recommends women consider a supplement of 400 micrograms of folic acid preconceptually to prevent the incidence of neural tube defects. In addition, it is suggested women capable of becoming pregnant consume a diet high in folic acid. Good sources of folic acid include oranges, green leafy vegetables, and fortified bread and cereals.

There is also a direct correlation between ethnicity, age, marital status, and educational status with increased negative pregnancy outcomes, such as low birth weight.

Pregnancy Weight Gain

Pregnancy is divided into three trimesters, with each trimester lasting three months, or approximately thirteen weeks (a normal pregnancy lasts 40 weeks). Recommendations for weight gain during pregnancy are based on the Institute of Medicine (IOM) definitions of prepregnancy BMI range. The BMI is defined as weight in pounds, divided by height in inches, divided by height in inches, multiplied by 703 (or weight in kilograms, divided by height in centimeters, divided by height in centimeters, multiplied by ten-thousand). The majority of weight gain should occur in the second and third trimesters. Weight gain can vary greatly in normal pregnancies with normal birth outcomes. Few studies have included women in their first trimester, so the importance of first-trimester weight gain on pregnancy outcome is unclear. However, a slow and steady rate of weight gain is considered ideal. The current recommended weight gain for the BMI ranges are outlined in the accompanying figure.

Poor weight gain during pregnancy is associated with prematurity, low birth weight, and small for gestational age. Among normal-weight women, weight gain above the recommended level corresponds to maternal fat stores and is not of benefit to fetal growth. In other words, fat gain during pregnancy parallels gestational weight gain, and women with greater weight gain also gain more fat. In addition, an inverse relationship exists between pre-pregnancy BMI and weight gain during pregnancy: women with a low pre-pregnancy BMI tend to gain more weight than women with a high prepregnancy BMI. On average, overweight women gain less weight than their thinner counterparts, though it is not unusual for obese women to achieve normal birth outcomes with less than the recommended weight gain.

In adolescent pregnancies, there are no established BMI recommendations regarding prepregnancy weight and weight gain. Excess weight gain, however, has been associated with postpartum obesity in adolescents.