Maternal and Neonatal Outcomes among Obese Women with Gestational Weight Gain above the New Institute of Medicine (IOM) Recommendations

The prevalence of obesity is increasing worldwide, and the rates have more than doubled since 1980 (1). World Health Organization (WHO) defines overweight and obesity as “abnormal or excessive fat accumulation that may impair health” (1). Body Mass Index (BMI) is commonly used to classify overweight (BMI 25.0–29.9 kg/m2), obesity (BMI ≥ 30.0 kg/m2), and super obesity (BMI ≥ 40.0 kg/m2) (2). WHO further categorizes obesity into three classifications: Obesity Class I (BMI range from 30 to 34.99), Obesity Class II (BMI range from 35 to 39.99), and Obesity Class III (BMI ≥ 40) (3) but does not differentiate between Obesity Class I, Obesity Class II, and Obesity Class III in relation to weight-gain recommendations for pregnant women (4). Obesity in reproductive-aged women has become a serious health issue (5). Further, a growing body of evidence demonstrates that pre-pregnancy obesity is associated with both adverse maternal and neonatal outcomes (6,7). Adverse maternal outcomes include gestational diabetes, preeclampsia, eclampsia, and Cesarean delivery (C-section) (8). Adverse neonatal outcomes can include macrosomia, respiratory distress, infection, and increased rates of Neonatal Intensive Care Unit (NICU) admission (9). To address concerns about the increasing prevalence of pre-pregnancy obesity and the associated maternal and neonatal risks, the Institute of Medicine (IOM) released new guidelines for gestational weight gain and provided a weekly weight-gain recommendation for the second and third trimesters (10). The new IOM guidelines, however, do not specify gestational weight-gain variations among different obesity classifications. Rather, the weight-gain recommendation for obese women is the same for all three WHO obesity classifications. The recommended range of total weight gain is 11-20 lbs., with a weekly weight gain of 0.5 lbs. in the second and third trimesters. Nevertheless, evidence suggests the impact of pre-pregnancy obesity on maternal and neonatal outcomes increases as the severity Abstract Objectives: Gestational weight gain is important for optimal maternal and neonatal outcomes. New Institute of Medicine (IOM) recommendations for gestational weight gain define obesity as body mass index (BMI) ≥30 and do not differentiate between maternal obesity classes. The recommended weight gain is 11-20 lbs. for obese women. The purpose of this study is to document prevalence of maternal obesity, excess gestational weight gain, and negative maternal and neonatal outcomes prior to 2009 IOM recommendations for gestational weight gain. Materials and Methods: This was a retrospective cohort study using Texas birth/infant death certificate data for 2005 through 2009, inclusive. The study population included 419,028 women. Those with excess (>20 lbs.) gestational weight gain were compared with those who gained the recommended 11-20 lbs. Results: Compared to the recommended weight-gain group, women in the excessive weight-gain group had lower percentage of gestational diabetes, across three obesity classes. Women with excessive weight gain had higher percentage of pre-eclampsia and Cesarean delivery (C-section) than women in the recommended weight-gain group. Babies of women with excessive weight gain in Obesity Class III had higher percentages of Neonatal Intensive Care Unit (NICU) admission, assisted ventilation >6 hours, surfactant therapy, and antibiotics for suspected sepsis than babies of women in Obesity Class III, gaining within the IOM recommendation. Conclusion: Findings suggest that the relationships between maternal obesity classification, gestational weight gain, and maternal and neonatal outcomes are complex. Further evidence is needed to make recommendations on gestational weight gain for obese women, stratified by the severity of obesity.