Differences in Outcomes in Obese (≥30), Morbidly Obese (≥40), and Super Morbidly Obese (≥50) Pregnancies
Authors: Santillan Mark K. , Mulanax Catalina , Thenuwara Kokila , Brandt Debra , Hunter Stephen K. , Knosp Boyd M. , Santillan Donna A. 
Published: May 2022

Background

Obesity in pregnancy is an increasing problem in the United States. Obesity in pregnancy can result in dangerous complications such as premature birth, cesarean delivery, gestational diabetes, and preeclampsia. Little is currently known about outcomes in the morbidly (body mass index (BMI) ≥40 kg/m2) and super morbidly obese (BMI ≥50 kg/m2) in pregnant patients. Consequently, it is difficult to adequately counsel patients and plan for delivery care. Most current data groups outcomes for obese patients in general, however, some aspects such as reductions in hormone concentrations in pregnancy vary markedly with increasing weight. Obesity can alter hormone concentrations in pregnancy. For example, significantly lower beta human chorionic gonadotropin concentrations and progesterone are observed with increasing weight. Thus, we hypothesized that there are differences outcomes between obese, morbidly obese, and super morbidly obese pregnancies. The purpose of this study (IRB #202004178) is to analyze pregnancy outcomes of women with body mass index (BMI) ≥40 kg/m2 in comparison to obese women with a BMI of 30‐35 kg/m2 with a more rigorous BMI classification system than has been previously used. Our hypothesis is that morbidly obese and super morbidly obese pregnant women will have significant differences in adverse outcomes compared to obese women.

Methods

A retrospective cohort study was performed comparing pregnancy outcomes of women with a BMI ≥ 30kg/m2 who delivered at the University of Iowa Hospitals and Clinics (UIHC) between 2009 and 2020. Data were extracted from the electronic health record (Epic) using the Intergenerational Health Knowledgebase, an enterprise data warehouse for research containing validated data from all pregnancies receiving care at UIHC. Additional data was extracted directly from the medical record. Women were included if they were ≥18 years old, had a singleton pregnancy and BMI ≥ 30 kg/m2, and delivered at UIHC (N=6445). Women were stratified into cohorts based on BMI (35‐39.9, 40‐49.9, 50‐59.9, 60‐69.9, 70‐79.9, ≥80 kg/m2) and compared to women with a BMI of 30‐35 kg/m2. Categorical variables were analyzed by chi square and continuous variables by t‐test. Regression models were created to control for confounding.

Results

Statistically significant increased incidences for gestational diabetes, preeclampsia, newborn hypoglycemia, number of days in the hospital post‐delivery, birthweight, and a composite poor neonatal outcome (P<0.001 for each outcome) were associated with increasing BMI. Both the 1‐ and 5‐minute APGAR scores worsened with increasing BMI (P< 0.001). However, there were decreased rates of caesarean section (P<0.001) and pre‐term birth (P=0.02) associated with increasing BMI. There were no statistically significant differences in neonatal ICU admission, death, respiratory distress, and pulmonary hypoplasia.

Conclusion

By identifying pregnancy outcomes using classifications with a smaller BMI range, it will be possible to develop more specific counseling and effective care plans for obese, morbidly obese, and super morbidly obese patients in the future.