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Pregnancy Nutrition Concerns

Weight Gain

Your midwife will be watching your weight to ensure that it is gained at an appropriate rate. Lack of weight gain or a sudden burst of weight gain may concern her. However, the steady weight gain does not mean you gain the same amount of weight every week. Most mothers only gain 2-4 pounds in the first trimester, begin gaining weight in the second trimester and may gain half a pound a week towards the end of pregnancy.

Here is the breakdown of where that extra weight goes:

7.5 lbs, baby
1 lb, placenta
2 lbs, uterus
2 lbs, amniotic fluid
1 lb, breast tissue
2.5 lbs, increased blood volume
5 lbs, fat
6 lbs, tissue fluids
27 lbs, Total

Appropriate Weight Gain

The 2009 Institute of Medicine Guidelines for appropriate weight gain are based on pre-pregnancy BMI. Pre-pregnancy BMI is only an estimate, but it is used in the gestational weight gain studies and is an easy number to calculate, so can be used to help determine the optimum weight gain.

BMI less than 18.5 : Gain 28-40 pounds

BMI 18.5-24.9: Gain 25-35 pounds

BMI 25-29.9: Gain 15-25 pounds

BMI 30 or more: Gain 11-20 pounds

Women who gain more weight than is considered appropriate are at increased risk for cesarean, large for gestational age babies (this is four times more likely), and macrosomia. High gestational weight gain is the strongest predictor of maternal overweight and obesity postbirth, with the risk of weight retention increasing as the gestational weight gain increases. In women who have already had a baby, the risk for emergency cesarean and large for gestational age increase with increasing gestational weight gain.

Excessive gestational weight gain is also associated with an increased risk of childhood obesity. In studies of pregnant rats, the children of rats who were over-fed during pregnancy have a greater taste for junk foods and increased fat tissue deposition, which could mean they will need to work harder to stay a healthy weight throughout their lives.

Women who gain less than what is considered appropriate are at increased risk for small for gestational age babies and low birth weight. Low gestational weight gain may also increase the risk of preterm birth in underweight women.

Women who are overweight or obese have another challenge during pregnancy. While normal weight women have an increase in insulin secretion and sensitivity during pregnancy that increases fat accumulation, overweight and obese women do not have the rise in peripheral insulin sensitivity. This causes a more pronounced insulin resistance in late pregnancy, leading to a higher risk for gestational diabetes.

For women who are overweight or obese before pregnancy, the gestational weight gain is a less strong predictor of fetal growth, and healthy babies are born with lower gestational weight gains. Recent evidence shows the lowest prevalence of adverse birth outcomes occur when obese women lose weight during pregnancy. For overweight and obese women, the lowest rate of preterm birth occurs among women who gain the least.

Characteristics of Weight Gain

Women who are overweight or obese before pregnancy are more likely to have gestational weight gain beyond the recommended ranges, despite gaining less weight overall. Women who have already had a child are up to four times more likely to exceed gestational weight gain recommendations than women having their first child, although women having their first baby gain more weight overall. This is likely due to the weight retention from the previous pregnancy moving the woman into a lower weight gain category.

Women who gain appropriate weight are more likely to report deliberate planning of meals and snacks to ensure only a modest increase in caloric intake, and to increase or maintain their pre-pregnancy physical activity. Women with an excessive weight gain were more likely to report feeling freedom to eat more food without concern and to exercise less during pregnancy.

Nutritional choices will have an impact on your weight gain regardless of your pre-pregnancy weight. Women who eat a junk food diet (defined by 2 or more cups of soft drinks per day;or consuming fast food meals, processed meat meals, or chips two or more times per week) were at risk for having a higher birth weight baby no matter what they weighed before becoming pregnant.

A review of the literature on pregnancy diets and gestational weight gain found a positive association between the amount of calories consumed and gestational weight gain. The caloric needs of pregnancy are about 300 additional calories per day during the second and third trimesters. Diets with less protein and a higher proportion of carbohydrates were associated with a lower gestational weight gain, however it is important to remember protein needs increase in pregnancy. The increase in protein is recommended to be about 10 g per day, for a total of 70 g.

For women with twin or higher order multiple pregnancies, there is little research on optimum diet or weight gain. Weight gain does begin earlier and occurs faster, with women gaining about 0.75 kg per week during the second and third trimesters. For twins, the optimum weight gain is considered about 20 kg. To achieve this weight gain a woman should aim for about 450 extra calories per day, not double the 300 extra calories per day recommended for singleton pregnancies.


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