Interpregnancy body mass index change and success of term vaginal birth after cesarean delivery.
OBJECTIVE
We investigated the effect of interpregnancy body mass index (BMI) change on success of term vaginal birth after cesarean (VBAC) among normal, overweight and obese women.


METHODS
Using 1992-2009 Washington State birth certificate data linked with hospitalization records, we conducted a population-based retrospective cohort study of nulliparous women (BMI ≥18.5 kg/m(2)) with a primary cesarean in their first birth and a term trial of labor in their second. Interpregnancy weight change (difference between first and second prepregnancy BMIs) was categorized as maintenance (<1 BMI unit change), loss (≥1 unit), moderate gain (≥1 and <2 units), high gain (≥2 units). We estimated relative risks of VBAC success using generalized linear models with a log-link function, adjusting for maternal age, race/ethnicity, nativity, marital status, education, smoking, primary cesarean indication, interpregnancy interval, birth year for second birth, and prenatal care adequacy.


RESULTS
Among 8302 women who attempted a term trial of labor, 65% had a successful VBAC. Women with normal BMI before their first pregnancy experienced an 8% decrease in VBAC success with moderate gain (relative risk [RR], 0.92; 95% confidence interval [CI], 0.87-0.98) and a 12% decrease in success with high gain (RR, 0.88; 95% CI, 0.83-0.93), compared with normal weight women who maintained weight. Weight loss increased VBAC success in women who were overweight (RR, 1.12; 95% CI, 1.01-1.25) or obese before their first delivery (RR, 1.24; 95% CI, 1.04-1.49), compared with overweight and obese women, respectively, who maintained weight.


CONCLUSIONS
Women can improve their chance of successful VBAC through interpregnancy weight management.
Department of Epidemiology, University of Washington School of Public Health, Seattle, WA; Department of Obstetrics and Gynecology, University of Washington School of Medicine, Seattle, WA; Health Services Research and Development, Puget Sound Health Care System, Department of Veterans Affairs, Seattle, WA. Electronic address: lcallega@uw.edu.
Lisa S
LS
Callegari
Department of Epidemiology, University of Washington School of Public Health, Seattle, WA.
Lauren A
LA
Sterling
Department of Epidemiology, University of Washington School of Public Health, Seattle, WA.
Sarah T
ST
Zelek
Department of Epidemiology, University of Washington School of Public Health, Seattle, WA.
Stephen E
SE
Hawes
Department of Epidemiology, University of Washington School of Public Health, Seattle, WA; Department of Obstetrics and Gynecology, University of Washington School of Medicine, Seattle, WA.
Susan D
SD
Reed
D000328:Adult; D015992:Body Mass Index; D015331:Cohort Studies; D005260:Female; D006801:Humans; D016014:Linear Models; D050177:Overweight / Q000150:complications*; D011247:Pregnancy; D012189:Retrospective Studies; D047929:Term Birth; D014219:Trial of Labor; D016064:Vaginal Birth after Cesarean / Q000706:statistics & numerical data*; D015430:Weight Gain; D055815:Young Adult
VBAC; body mass index; interpregnancy weight change; obesity; vaginal birth after cesarean