Nutrition in Pregnancy

Prepregnancy and Nutrition

The nutritional status of the mother at the time of conception is an important determinant of fetal growth and development. Being a healthy weight before conception (body mass index [BMI], 18.5–24.9 kg/m 2) is of great importance, and being underweight (BMI, less than 18.5kg/m 2) or overweight (BMI, more than 25kg/m 2) can affect both fertility and birth outcome. There is now evidence to confirm that folic acid, found in many foods such as green leafy vegetables, fortified cereals, and bread, is of great importance during the period from before conception to early pregnancy and can reduce the risk of neural tube defects. Women planning a pregnancy are advised to take 400 grams a day of folic acid supplement before and up to the 12th week of pregnancy to ensure that they meet this recommendation.

Nutritional Requirements and Weight Management during Pregnancy

Nutritional requirements are increased during pregnancy. Additional maternal stores of energy and nutrients are required for fetal development, as well as for lactation postpregnancy. During pregnancy, women have large variations in fat deposition, energy expenditure, and physical activity; this reflects the wide variation in energy requirements in women. For women with a normal prepregnancy BMI, only a small amount of additional energy is required. This is because in pregnancy, the body adapts to the increased energy requirements and becomes more energy efficient through reduced physical activity and a lowered metabolic rate. It is only during the last trimester of pregnancy that there are increased energy requirements of an additional 200 kcal/day. However, underweight women or women who remain active and do not reduce their activity levels may require more energy.

Studies have shown that women with a healthy prepregnancy BMI have a weight gain on average of around 12 kg (10–14 kg), which is associated with the lowest risk of complications in pregnancy and labor, and a lowered risk of having a low-birth-weight (LBW) baby (birth weight, less than 2.5 kg). Other risk factors associated with a LBW baby are smoking and use of alcohol or drugs during pregnancy. LBW is associated with increased infant morbidity and mortality, as well as an increased risk of diseases in later life, such as cardiovascular disease and type 2 diabetes.

The “Barker” hypothesis states that impaired intrauterine growth and development may be the root cause of many degenerative diseases of later life through the mechanism of fetal programming, in which a stimulus or insult at a critical period in early life development has a permanent effect on the structure, physiology, or function of different organs and tissues. A review by the World Health Organization showed that a birth weight of 3.1–3.6 kg is considered in the normal range and is associated with positive fetal outcomes for a baby born full term. Excessive weight gain during pregnancy can increase the risk of complications such as high blood pressure, and in the long term it can lead to overweight and obesity in the mother postpartum.

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