Association of pre-pregnancy body-mass-index and gestational weight gain with preterm singleton birth in women with cervical cerclage: a retrospective cohort study.

OBEJECTIVE: To examine the correlations of pre-pregnancy Body-Mass-Index (BMI) and Gestational Weight Gain (GWG) with preterm singleton delivery among American women with cervical cerclage.

METHODS

This is a retrospective cohort study of 33822 pregnant women with cervical cerclage selected from the National Vital Statistics System (NVSS) 2009-2013 database. GWG was converted to gestational age-standardized z scores. Associations of pre-pregnancy BMI and GWG with preterm birth risk were evaluated using risk factor-adjusted log-binomial regression models.

RESULTS

Preterm birth accounted for 10378 (30.68%) of the pregnancies in our research. Women with pre-pregnancy overweight and obesity were both associated with a significantly higher risk of preterm birth than those with normal weight (RR(95% CI): 1.06(1.02,1.10), P = 0.007;RR(95% CI): 1.13(1.09,1.17), P < 0.001). Preterm birth risks were higher in pre-pregnancy underweight women with low GWG z scores (RR(95% CI): 1.52(1.26,1.84), P < 0.001). Among pre-pregnancy normal-weight women, those with low (RR(95% CI): 1.17(1.10,1.24), P < 0.001) or high (RR(95% CI): 1.23(1.14,1.33, P < 0.001) GWG z scores both had an increased risk of preterm birth. Preterm birth risks were higher in women with pre-pregnancy overweight when they had high GWG z scores (RR(95% CI): 1.20(1.10,1.32), P < 0.001). Among women with pre-pregnancy obesity, those with high GWG z scores had increased preterm birth risks (RR(95% CI): 1.20(1.14,1.27), P < 0.001). Notably, there was a significant reduction in preterm birth risk among women with low GWG z scores in the pre-pregnancy obesity group (RR(95% CI): 0.88(0.81,0.95), P = 0.002).

CONCLUSIONS

Pregnant women with cervical cerclage should maintain an appropriate weight before and during pregnancy, suggesting that more tailored weight control and prenatal care should be provided to pregnant women according to their pre-pregnancy BMI.