Primiparity association with an increased risk for preterm birth among women with short cervical length

Evaluating the influence of parity on the relationship between short cervical length and preterm birth The study took place within a health maintenance organization (HMO) with more than 2.5 million insured population. HMO databases were retrospectively searched between the years 2012-2020. Data was extracted for women with short cervical length (measured below 25mm) between 19+0 and 23+6 weeks of pregnancy. The women were categorized by their parity to primiparous and multiparous. The primary outcome measured was preterm birth before 37 weeks of pregnancy. Data was analyzed by adjusted multivariable logistic regression. 738 women were included in the analysis, 259 nulliparous and 479 multiparous. 62.2% of the women had routine cervical measurement (for example, as a part fetal US scan) and 37.8% of the women had cervical length measurement because they were symptomatic. 66.3% of the study population had progesterone treatment during the pregnancy, 20.6% received betamethasone treatment and 9.9% received tocolytic treatment. 22.4% of the women eventually had preterm birth. After adjustment and performing multivariable logistic regression, nulliparous women with short cervical length had an odds ratio (OR) of 1.55 for preterm birth compared to multipara women (p < 0.05, CI 1.07-2.24). Among women with short cervical length, nulliparity increases the risk for preterm birth. This evidence can guide medical professionals in planning pregnancy follow-up and treatment for nullipara women.