Weekly Differences in the Prevalence of a Short Cervix at 18+0 to 23+6 Weeks of Gestation in Pregnant Women with and without a History of Preterm Delivery.

ABSTRACT

OBJECTIVE: The study aimed to estimate weekly differences in the prevalence of a short cervix during the period of 18+0 to 23+6 weeks of gestation in pregnant women with and without a history of previous preterm delivery (PTD). DESIGN: An observational study was conducted. METHODS: Setting and participants: 20,002 pregnant women, 18,591 without a history of previous PTD (low risk) and 1,411 with at least one previous PTD (high risk), were evaluated at 18+0 to 23+6 weeks + days of gestation. Weekly differences in the prevalence of a short cervix (≤25 mm, ≤20 mm, and ≤15 mm) between women with and without previous PTD were estimated. RESULTS: High-risk women had a significantly higher prevalence of a short cervix, defined as either ≤25 mm (4.4% vs. 2.2%; p < 0.0001) or ≤20 mm (2.4% vs. 1.2%; p < 0.0001) but not for ≤15 mm (1.2% vs. 0.9%; p < 0.2) as compared to low-risk pregnant women. The odds ratio for a short cervix ≤25 mm in high-risk as compared to low-risk women was 2.0 (95% CI 1.54-2.61; p < 0.0001). Among low-risk women, those evaluated at 22 or 23 weeks of gestation had a significantly higher prevalence of a short cervix ≤25 mm (3.8% vs. 1.9%; p < 0.0001), ≤20 mm (2.4% vs. 0.98%; p < 0.0001), and ≤15 mm (1.6% vs. 0.7%; p < 0.0001) than low-risk women scanned between 18 and 21 weeks of gestation. Similar results were observed for high-risk women. LIMITATIONS: No gestational age at delivery was evaluated. CONCLUSION: There is higher prevalence of short cervix when pregnant women are evaluated at 22+0 to 23+6 than at 18+0 to 21+6 weeks of gestation.