Association Between Elevated Maternal BMI, Cervical Length, and Spontaneous Preterm Birth in Persons at Increased Risk of Spontaneous Preterm Birth

Objectives

To evaluate the association between maternal BMI, short cervical length (CL) ≤2.50 cm, and spontaneous preterm birth (SPTB) in persons with risk factors for SPTB, including those with a history of excisional cervical procedures or uterine anomalies.

Methods

This retrospective cohort study included asymptomatic pregnant persons with singleton gestations and intact membranes, without a history of SPTB but at increased risk of SPTB (including those with a history of excisional cervical procedures or uterine anomalies), who underwent transvaginal ultrasound assessment of CL between 16⁰ and 23⁶ weeks gestation and had pre-pregnancy BMI (or height and weight) reported. The primary exposure was pre-pregnancy BMI, with the primary outcomes of interest being CL and SPTB. Univariate and multivariate logistic regression analyses were performed to assess the associations between BMI and CL and BMI and SPTB <37 weeks gestation, adjusting for possible confounders.

Results

Of the 407 persons included, 198 (48.6%) had a BMI ≥25.0. BMI ≥25.0 and CL ≤2.50 cm were associated with SPTB <37 weeks gestation (adjusted OR 2.65; 95% CI 1.09–6.43, P = 0.031 and adjusted OR 7.30; 95% CI 2.18–24.50, P = 0.001; respectively). BMI ≥25.0 was not associated with CL ≤2.50 cm in the univariate or multivariate regression analyses (P = 0.29 and P = 0.48, respectively).

Conclusions

In persons with a history of an excisional cervical procedure or uterine anomaly, BMI ≥25.0 is associated with SPTB <37 weeks gestation but is not associated with CL ≤2.50 cm in the second trimester.