Uterine leiomyomata and cesarean birth risk: a prospective cohort with standardized imaging

To determine if women with leiomyomata detected using uniform ultrasound methods are at increased risk of cesarean birth, without regard to indication.

Women were enrolled in Right from the Start (2000-2010), a prospective pregnancy cohort. Leiomyomata were counted, categorized, and measured during first trimester ultrasounds. Women provided information about demographics and reproductive history during first trimester interviews. Route of delivery was extracted from medical records or vital records, if the former were unavailable. Generalized estimating equations were used to calculate risk ratios (RR) and 95% confidence intervals (CIs) for the risk of cesarean birth by leiomyoma presence and characteristics.

Among 2635 women, the prevalences of leiomyomata and cesarean birth were 11.2% and 29.8%, respectively. Women with leiomyomata, compared with those without, had a 27% increase in cesarean risk (RR, 1.27; CI, 1.17-1.37). The association was weaker following adjustment for maternal body mass index and age (adjusted risk ratio [ARR], 1.11; CI, 1.02-1.20). The adjusted risk was elevated for women with a single leiomyoma 3 cm or more in diameter (ARR, 1.22; CI, 1.14-1.32) and women with the largest total leiomyoma volumes (ARR, 1.59; CI, 1.44-1.76).

Women with leiomyomata were at increased risk for cesarean birth particularly, those with larger tumor volumes.