Prepregnancy Obesity and Primary Cesareans among Otherwise Low-Risk Mothers in 38 U.S. States in 2012.
BACKGROUND
The United States has recently experienced increases in both its rate of obesity and its cesarean rate. Our objective was to use a new item measuring prepregnancy body mass index (BMI) on the U.S. Standard Certificate of Live Birth to examine at a population level the relationship between maternal obesity and primary cesarean delivery for women at otherwise low risk for cesarean delivery.


METHODS
By 2012, 38 states with 86 percent of United States births had adopted the U.S. Standard Certificate. The sample was limited to the 2,233,144 women who had a singleton, vertex, term (37-41 weeks) birth in 2012 and no prior cesarean. We modeled the likelihood of a primary cesarean by BMI category, controlling for maternal socio-demographic and medical characteristics.


RESULTS
Overall, 46.4 percent of otherwise low-risk mothers had a prepregnancy BMI in the overweight (25.1%) or obese (21.3%) categories, with the obese category distributed as follows: obese I (BMI 30.0-34.9, 12.4%); obese II (BMI 35.0-39.9, 5.5%); and obese III (BMI 40+, 3.5%). Obesity rates were highest among American Indian and Alaska Native (32.5%) and non-Hispanic black mothers (30.5%). After adjustment for demographic and medical risks, the adjusted risk ratios (95% confidence intervals) of cesarean for low-risk primiparas were: 1.61 (1.60-1.63) for obese I, 1.86 (1.83-1.88) for obese II, and 2.21 (2.18-2.25) for obese III mothers compared with mothers in the normal weight category.


CONCLUSIONS
A relationship between prepregnancy obesity and primary cesarean delivery among relatively low-risk mothers remained even after controlling for social and medical risk factors.
Department of Community Health Sciences, Boston University School of Public Health, Boston, MA, USA.
Eugene
E
Declercq
Maryland Population Research Center, University of Maryland, College Park, MD, USA.
Marian
M
MacDorman
Division of Vital Statistics, Reproductive Statistics Branch, National Center for Health Statistics, CDC, Hyattsville, MD, USA.
Michelle
M
Osterman
Department of Community Health Sciences, Boston University School of Public Health, Boston, MA, USA.
Candice
C
Belanoff
Department of Obstetrics and Gynecology, Boston University School of Medicine, Boston, MA, USA.
Ronald
R
Iverson
D000328:Adult; D015992:Body Mass Index; D002585:Cesarean Section / Q000009:adverse effects / Q000379:methods / Q000706:statistics & numerical data; D015331:Cohort Studies; D003710:Demography; D005260:Female; D006801:Humans; D016013:Likelihood Functions; D009765:Obesity / Q000150:complications / Q000175:diagnosis / Q000453:epidemiology; D011247:Pregnancy; D011248:Pregnancy Complications / Q000175:diagnosis / Q000453:epidemiology; D012189:Retrospective Studies; D012307:Risk Factors; D012959:Socioeconomic Factors; D014481:United States / Q000453:epidemiology
cesarean delivery; obesity; prepregnancy obesity