The impact of preconception body mass index on cervical length: a prospective cohort study in China

Objective: To assess the relationship between preconception body mass index (BMI) and cervical length (CL). Methods: Data was collected from a prospective cohort study conducted in Beijing, China. A total of 4843 qualified women participated in this study, whose health-related information was recorded at the very beginning and their cervical length was measured with transvaginal ultrasound examination during 22-24 gestational weeks. Logistic regression was used to evaluate the relationship between preconception BMI and cervical length, after adjusting for potential confounders. Results: Of all the participants in the analysis, 580 (12.0%) women had a short cervical length (CL less than 30 mm). After adjusting for the age and parity status, the adjusted odds ratios of short CL for underweight: adjusted OR = 1.28 (95% CI: 1.02, 1.60); overweight: adjusted OR = 0.74 (95% CI: 0.55, 0.99); obesity: adjusted OR = 0.38 (95% CI: 0.17, 0.88) compared with normal weight. The mean CL in underweight, normal weight, overweight and obesity group demonstrated a significant linear increased trend (33.47, 34.16 and 34.96 mm, respectively) (p < .05), dependent of age and parity. Conclusions: This research revealed that low preconception BMI women were more likely to have a short CL.