Effects of Gestational Weight Gain on Delivery Outcomes in an Obese, Low-Income Population

Allison Archer Sellner, MD; Abigail Hook Garbarino, MD, DiMiao, PhD; Lisa Marie Hollier, MD, MPH; Bani Maheshwari Ratan, MD


South Med J. 2021;114(11):686-691. 

In This Article


This study was approved by the institutional review board of our institution. We conducted a retrospective cohort study of 1428 women with prepregnancy BMI ≥30 who received prenatal care at a large Medicaid clinic. Prenatal care visits and deliveries were performed by faculty members from September 2013 to August 2017. Eligible women were nonsmokers with a singleton delivery who initiated care before 20 weeks and had a BMI ≥30. GA was calculated using the last menstrual period and/or ultrasound according to the guidelines specified by the American College of Obstetricians and Gynecologists.[18] For women with multiple pregnancies during this study, each pregnancy was counted as a separate encounter. Demographic data obtained from the electronic medical record included age, race, marital status, gravidity, parity, medical comorbidities, participation in group prenatal care, attendance at nutrition consult, and planned versus unplanned nature of pregnancy.

Prepregnancy BMI was calculated by the electronic medical record based on patients' self-reported prepregnancy weight and measured height at the initial visit. Women's prepregnancy BMI was categorized as obesity class 1 (BMI 30.0–34.9), class 2 (BMI 35.0–39.9), and class 3 (BMI ≥40). Total gestational weight gain was calculated as the difference between measured weight recorded at the last prenatal visit before delivery and self-reported prepregnancy weight. To calculate whether gestational weight change was below or in excess of recommendations, we used previously validated formulas that were derived from the National Academy of Medicine.[5,19,20] The guidelines state that regardless of prepregnancy BMI, a minimum of 1.1 lb and a maximum of 4.4 lb should be gained during the first trimester. From the second trimester onward, for women with a BMI ≥30, the recommendations for weight gain are 0.4–0.6 lb/week. As such, the lower limit of weight gain was 1.1 + 0.4 (GA –13) and the upper limit of weight gain was 4.4 + 0.6 (GA – 13). We classified gestational weight change into four categories: weight gain within the National Academy of Medicine guidelines, weight gain above the National Academy of Medicine guidelines, weight gain below the National Academy of Medicine guidelines, and weight loss.

The primary outcomes studied were SGA (less than the 10th percentile for birth weight), LGA (greater than the 90th percentile for birth weight), and mode of delivery (scheduled cesarean section, cesarean section during labor, or vaginal delivery). The 2010 Olsen growth charts were used to determine birth weight percentile in relation to GA and sex.[21] Forceps and vacuum deliveries were included as vaginal deliveries. Cesarean sections were classified into those that were performed after a trial of labor (cesarean section during labor) and those that were performed without a trial of labor (scheduled). Cesarean section indications of arrest of dilation, arrest of descent, nonreassuring fetal status, failed induction, abruption, and cord prolapse were classified as patient undergoing trial of labor. Cesarean section indications of malpresentation, planned repeat, genital herpes outbreak, history of shoulder dystocia, history of myomectomy, placenta previa, unstable maternal or fetal status remote from delivery, and history of 4th degree laceration were classified as scheduled cesarean sections. Secondary outcomes that were studied included preterm delivery (delivery before 37 weeks), preterm labor (delivery before 37 weeks because of labor), gestational diabetes mellitus, and gestational hypertension.

Univariate logistic regression analysis was used to compare gestational weight gain and SGA, LGA, and delivery type and secondary outcomes stratified by obesity class. Multinomial logistical regression analysis was then performed while adjusting for age, race/ethnicity, nutritional education, participation in group prenatal care, and medical conditions. The referent group within each BMI category was gestational weight gain within the normal range. Statistical significance was set as P < 0.05. All of the statistical analyses were performed using StataSE 14 (StataCorp, College Station, TX).