This study investigates the relationship between perinatal outcomes and gestational weight gain, as classified by category of compliance with the 2009 IOM guidelines for gestational weight gain, in women with T2DM who were either overweight or obese. This is the first study to investigate the interaction between high maternal prepregnancy BMI, gestational weight gain, and perinatal outcomes in women with T2DM.
Our findings suggest that the 2009 IOM guidelines are indeed applicable to women with T2DM who are either overweight or obese.
We observed that women with gestational weight gain beyond the recommended amount were significantly more likely to experience adverse maternal outcomes, namely cesarean delivery, as well as increased likelihood of neonatal macrosomia. Of note, on univariate analysis, we initially noted a decreased incidence of SGA and IUFD and increased rate of NICU admission in women with excessive gestational weight gain; these findings did not persist in multivariable analysis. For the outcome of IUFD, we analyzed data by gestational weight gain per week, and found no incidence of IUFD among those with weight gain (per week) within guidelines.
Our findings are consistent with prior studies indicating that excessive gestational weight gain in populations of nondiabetic women or women with GDM is associated with increased likelihood of cesarean delivery and neonatal macrosomia. We also found that overweight or obese women with T2DM who have weight gain per week greater than the IOM guidelines were at risk for preterm birth. In contrast, we did not observe an association between maternal or neonatal morbidity and less-than-recommended weight gain in overweight/obese women with T2DM. Based on these findings, we speculate that overweight/obese diabetic women with low gestational weight gain are somewhat protected against preterm birth, perhaps because adequate nutritional stores are already present and less than IOM-recommended weight gain may be adequate. One limitation of this specific finding, however, is that in this study, we were unable to calculate per-trimester weight gain in this population, because we only had available data on total weight gain, from prepregnancy to last clinic visit. As a result, we cannot precisely estimate the rate of gestational weight gain along a specific per-trimester sigmoid curve, which would more accurately describe the pattern of weight gain in most pregnancies. It is possible that this finding that women with excess weight gain per week are at increased risk of preterm birth is due to our calculation of gestational weight gain as a linear pattern; future work should assess this outcome with more accurate per-trimester rates of weekly weight gain to clarify risk of preterm birth.
Women with T2DM are at risk of maternal and neonatal complications in pregnancy, and being overweight or obese with excessive gestational weight gain appears to compound this risk. Of particular concern is the relationship between excessive weight gain and neonatal macrosomia, as literature would suggest an association between elevated birth weight and long-term childhood health outcomes.14
Furthermore, the rising cesarean delivery rate in the United States is worrisome, and it appears that excessive weight gain in obese and overweight diabetic women is a strong risk factor for cesarean delivery. However, gestational weight gain is a modifiable risk factor for adverse outcomes. These data suggest that at least the upper limits of the 2009 IOM recommendations should be applied to this population of overweight and obese T2DM women during prenatal visits, particularly integrating patient education, medical as well nutritional interventions, and exercise recommendations as an integral part of their health care. However, as we were not powered to examine further strata within the IOM guideline recommendations, larger studies should attempt to identify if even lower thresholds for weight gain may improve outcomes in women with T2DM. Going forward, the specific actions recommended by the IOM in the new guidelines should also include recommendations for the populations of overweight and obese diabetic women.4
There are few data to suggest how to manage weight in this population of overweight and obese diabetic women during pregnancy. Based on these data, we would recommend that intensive patient education regarding weight gain goals take place preconceptionally when possible, and then early and regularly during pregnancy, consistent with a recent randomized trial.15
However, further research is required to better understand how to perform successful interventions to improve adherence to the 2009 IOM guidelines in a diabetic population. Further, other studies have suggested that there may be room for even tighter weight gain guidelines in some categories of obese women, while still balancing the risks associated with inadequate nutrition.16–19
This question remains controversial even in a nondiabetic obese population, and we would suggest more work is needed to identify whether narrower guidelines might be safe and beneficial in a diabetic obese population.
This study is limited by the retrospective nature of this cohort study, which is prone to confounding bias. While we attempt to control for potential confounding factors by implementing multivariable logistic regression analyses for effect estimates, there may be uncontrolled confounding from unmeasured or unobserved factors for which we did not have information or could not account for by statistical models. Additionally, there are a number of outcomes associated with diabetes in pregnancy which we could not examine due to lack of information collection. For example, ideally, we would like to examine the association between gestational weight gain and preeclampsia, and other maternal outcomes such as postpartum hemorrhage or severe lacerations, indications for cesarean and operative vaginal deliveries, and degree of glycemic control to further ascertain the role of gestational weight gain in women with diabetes in pregnancy. We additionally do not know the reasons for preterm delivery in this population, although we suspect that the rate of preterm delivery reflects the underlying risk of having T2DM, as literature suggests women with T2DM have an increased risk of both spontaneous and iatrogenic preterm birth.20,21
Further, we could not examine neonatal outcomes often associated with pregnancies complicated by insulin resistance, such as neonatal hypoglycemia, jaundice, and other metabolic derangements. One additional limitation is that these data are from a specific population of overweight and obese women, largely Latina, receiving specialized care in a population program; as a result, these data may not be generalizable to a population of normal-weight diabetic women or to a population with a different racial and ethnic distribution. Finally, because of the observational nature of these data, we cannot claim a causal relationship between gestational weight gain and adverse outcomes. As there are no prior data that apply the 2009 IOM guidelines to this population of women and since it is not possible to perform randomized controlled studies that assign women to various amount of gestational weight gain, we believe that the large sample size and statistical models may provide valid information that may be useful in caring for this high-risk population.
Our study validates the revised IOM guidelines for narrower gestational weight gain in a population of overweight and obese women with T2DM. Our findings suggest that excessive weight gain beyond the IOM guidelines is associated with adverse maternal and neonatal outcomes in overweight and obese women with T2DM. Women with T2DM who experience less than the recommended weight gain do not appear to have significantly worsened perinatal outcomes. We would suggest that these new guidelines be aggressively utilized in the clinical setting for overweight and obese women with T2DM, and that further research investigate whether perhaps even narrower guidelines are warranted for this population.