Managing Obesity During Pregnancy
In the postpartum period, we must help women meet the important goal of returning to their prepregnancy weight, and then encourage them to lower their weight before the next pregnancy, referring them to specialists if necessary to break the cycle of obesity.
Breastfeeding is an important tool to reducing postpartum weight retention—it increases caloric utilization by 500-800 calories per day and has short- and long-term benefits for both the mother and the baby. We must appreciate, however, that it is technically more difficult for an obese woman to breastfeed, compared to a nonobese woman. The obese patient may need special help from a lactation consultant.
▸ Think inflammation and insulin resistance. In the pregravid state, an obese woman has increased inflammation and more insulin resistance to begin with. Her inflammatory profile and level of insulin resistance then only increases in pregnancy. (There are significant 50%-60% decreases in maternal insulin sensitivity by the end of the third trimester.)
Increased insulin resistance in pregnancy, studies show, can drive an excess flow of nutrients to the fetus and lead to macrosomia. Insulin resistance also may increase the risk of preeclampsia and gestational diabetes.
Although insulin sensitizers such as metformin or thiazolidinediones theoretically may be useful for increasing insulin sensitivity, these agents cross the placenta and their fetal safety has not been documented. This brings us back to lifestyle interventions to improve insulin resistance—a calorie-appropriate diet that is low in saturated fat and high in complex carbohydrates, for instance, along with exercise that uses large skeletal muscles, such as walking and swimming.
The role of dietary supplements such as fish oil and vitamin D in decreasing inflammation and improving metabolic function are currently under investigation. While we do not believe either causes any harm, it is too early to make official recommendations. At this point, we must focus on lifestyle interventions as our primary management approach.
▸ Pursue early glucose testing, and tight glucose control in patients with gestational diabetes mellitus (GDM). Women who are obese should be considered for early glucose screening rather than waiting until the 24- to 28-week standard screening period. Such early screening enables the detection of undiagnosed type 2 diabetes, or overt diabetes, and is the new recommendation of the International Association of Diabetes and Pregnancy Study Groups (IADPSG) for the diagnosis of GDM (Diabetes Care 2010;33:676-82).
When results from early screening are normal, testing should be repeated later. If either pregestational diabetes or gestational diabetes is detected, tight glucose control should be the goal.
A recent paper from the Hyperglycemia and Adverse Pregnancy Outcome (HAPO) study suggests there are strong independent associations of fasting C-peptide (an index of insulin sensitivity) and BMI with preeclampsia. Maternal glucose levels in this study (levels below those found in diabetes mellitus) had weaker associations with preeclampsia (Am. J. Obstet. Gynecol. 2010;202:255.e1-7).
Other data show that tight glucose control in obese women with diabetes may decrease the risk of preeclampsia and other complications.
▸ Limit weight gain in pregnancy. Although pregravid weight, rather than weight gain during pregnancy, has the strongest correlation with the complications of maternal obesity in pregnancy and with birth weight, maternal weight gain during gestation still is positively correlated with excess birth weight and with various complications.
At minimum, we can work with women on limiting weight gain in pregnancy and following the new guidelines published last year by the Institute of Medicine and National Research Council. The report, which updates the previously published guidelines from 1990, specifies a new weight gain range for obese women, limiting their gain to 11-20 pounds during pregnancy.
Studies published after the previous guidelines were released in 1990 have consistently shown that women who gain weight within the recommended amounts have better outcomes. Women who do not gain excess weight also are less likely to retain extra pounds after birth.
Research also has shown, however, that a high proportion of women report that they were either given no advice on how much weight to gain or were advised to gain outside of their recommended range.
Indeed, an increasingly large proportion of women has gained in excess of the recommendations: From 1993 to 2003, the proportion of overweight women gaining in excess of the 1990 IOM recommendations increased to approximately 63%; approximately 46% of obese women gained excess weight.
Given the IOM's lower weight gain recommendation for obese women, such proportions will likely rise unless we increase the counseling we give patients on weight, diet, and exercise, and unless we routinely record and discuss patients' weight, height, and BMI.
