The link between pregnancy and obesity

An important contributing factor to weight gain among young adult women is sustained weight retention after pregnancy. Although studies of the general population have reported average weight gains of only 0.4-3.8 kg more than aging, there is marked variability in weight changes that are associated with pregnancy. Approximately 25% of women experience weight retention of ≥4.5 kg in association with pregnancy. Moreover, weight changes at the time of pregnancy are related strongly to subsequent weight change. In 2 large prospective studies, weight gains during the pregnancy and weight changes during the year after delivery were both independently related to the development of overweight or weight gain at 15 and 10 years follow-up evaluations, respectively. Linne et al reported that 45.6% of normal weight individuals who gained excessive amounts of weight during pregnancy (average, 18.8 kg) shifted from normal weight to overweight at the 15-year follow-up evaluation ( Figure 1 ). Moreover, 43.8% of normal-weight women who had retained significant amounts of weight at 12 months after delivery (M = 4.8 kg) had become overweight by the 15-year follow-up evaluation. Rooney and Schauberger reported that women who were back to their prepregnancy weight by 6 months after delivery gained only 2.4 kg over the next 10 years, whereas those who retained weight after delivery gained 8.3 kg over the 10-year follow-up period. Thus, high gestational weight gain and postpartum weight retention appear to set the stage for future weight gain and the development of obesity in women.

Prevalence of overweight and obesity among women who had low, middle, and high weight gains during pregnancy

Women who experienced low-weight gain gained an average of 9.8 ± 1.9 kg; women who experienced middle-weight gain gained an average of 14.0 ± 0.9 kg; and women who experienced high-weight gain gained an average of 18.8 ± 2.3 kg during pregnancy. Adapted from Linne et al.

Phelan. Teachable moment: weight control and obesity prevention. Am J Obstet Gynecol 2010.

Variables associated with high postpartum weight retention provide targets for intervention

The strongest predictor of 1-year postpartum weight retention is the amount of weight gained during pregnancy. The Institute of Medicine (IOM) guidelines were developed in 1990 to provide recommended ranges of weight gain to optimize fetal growth and maternal/infant outcomes. Recently, the recommendations were revised to use the BMI cutpoints from the World Health Organization (eg, overweight = 25.0-29.9 km/m ² instead of 26.0-29.9 km/m ² ) and provide a specific range of weight gain for obese women (≥30.0 km/m ² ), previously lacking from the 1990 guidelines ( Table ). Despite the wide adoption of the 1990 IOM guidelines, however, many women continue to gain more than the recommended amount. Available data suggest that 37% of normal-weight women and 64% of overweight women gain more that IOM recommendations. Although there is a broad range of weight changes that are associated with healthy pregnancy outcomes, weight gains that exceed the IOM recommended levels have been connected to gestational complications (hypertension, diabetes mellitus, and preeclampsia), complications in delivery (cesarean section deliveries), babies that are large for gestational age (macrosomia), and obesity in offspring by age 3 years. Weight gains outside IOM recommendations are also associated with greater postpartum weight retention and an increased risk of future overweight. Thus, to prevent postpartum weight retention, it is critical to try to prevent excessive weight gain during pregnancy.

Behaviors during pregnancy have also been found to relate to the risk of excessive gestational weight gain ( Figure 2 ). Olson and Strawderman evaluated multivariable biopsychosocial models of gestational weight gain in 622 healthy women. In the final adjusted model, women who reported eating “much more” food during mid pregnancy were 2.35 times more likely than women who ate “a little more” food to gain too much weight in pregnancy. Moreover, women who were less physically active during pregnancy than before pregnancy were 1.7 times more likely to gain more than recommended than those who maintained or increased their physical activity. Other studies have reported similar findings and also have shown additional relationships with excessive gestational weight gain and high fat intake, low fiber intake, and high intake of sweets. These findings suggest that targeting healthy eating and modest physical activity during pregnancy may help to improve maternal weight gain outcomes ( Figure 2 ).

Variables related to excessive gestational weight gain

Phelan. Teachable moment: weight control and obesity prevention. Am J Obstet Gynecol 2010.

At-risk populations

Certain subgroups of women appear to be at greater risk of high gestational weight gain than others and may benefit from interventions to promote healthy weight gain during pregnancy. Many studies have found that prepregnancy weight is a significant predictor of weight changes during pregnancy. Although overweight women gain less weight than normal-weight women during pregnancy, women who are overweight before pregnancy appear more likely to exceed IOM weight gain guidelines (with the 1990 IOM overweight criterion of BMI ≥26 kg/m ² ) compared with normal-weight women. The multiple risks that are associated with excess gestational weight gain may be compounded by risks that are associated with high prepregnancy BMI. Compared with normal-weight women, obese pregnant women have an increased risk of early-trimester loss and recurrent miscarriage and congenital anomalies that include neural tube defects, heart defects, and omphalocele. Other complications include chronic hypertension, pregnancy-induced hypertension, pregestational diabetes mellitus, gestational diabetes mellitus, postdate delivery, urinary tract infection, asthma, obstructive sleep apnea, and gallbladder disease. Numerous delivery, operative, and postpartum complications are also associated with prepregnancy obesity. Moreover, maternal obesity has a significant impact on offspring risks, which include higher rates of fetal macrosomia, still birth and childhood obesity.

Weight loss before conception is likely to be an effective way to decrease complications that are associated with pregnancy in obese women; however, limited research has been conducted in this area. Bariatric procedures before conception have been found to reduce significantly the rates of pregnancy-induced hypertension and gestational diabetes mellitus, chronic hypertension, pregestational diabetes mellitus, and large-for-gestational-age infants. However, bariatric surgery is a potential option for only a small subset of women who have a BMI >35 kg/m ² , comorbid conditions, history of failed nonsurgical interventions, acceptable operative risks, and motivation to adhere to long-term postsurgical dietary regimen. Practitioners may consider advising effective nonsurgical weight loss strategies before conception, which would include daily self-monitoring food intake, daily self-weighing, and consuming meal replacement products, typically for 2 meals a day initially and then 1 meal a day long term. However, because physicians often cannot devote the time that is needed to help a patient with their weight loss efforts, it may be useful to refer patients to other programs that can provide more intensive assistance with weight loss before conception. Ideally, efforts to promote prepregnancy weight control should be carried over during pregnancy to prevent excessive gestational weight gain.

Race may also affect pregnancy weight changes. African American women consistently gain less weight than white women during pregnancy. However, they are generally no different from white women in terms of falling above, at, or below IOM guidelines. Age also affects weight gain during pregnancy; younger women gain more weight than older women, but this effect may be due to high weight gain during growth in adolescent women. Primiparity is also associated with larger weight gains during pregnancy. Abrams and Parker found that weight gains of women with parity of 0, 1, or ≥2 were 34.0, 33.2, and 31.5 lbs, respectively. In another study, 34% of primiparous women exceeded the 1990 IOM guidelines; only 16% of multiparous women exceeded the guidelines.

Smoking cessation is strongly recommended during pregnancy because, in part, of its association with low infant birthweight. Studies that have compared women who do not smoke with those who continue to smoke have found that nonsmokers tend to gain more weight than smokers. Smoking during pregnancy has also been associated with increased risk of obesity in the offspring. Low income has been related to greater risk of exceeding weight gain guidelines. Finally, genetic factors may contribute to the rate of gestational weight gain.