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

<b><i>Objective:</i></b> 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). <b><i>Design:</i></b> An observational study was conducted. <b><i>Methods:</i></b> <i>Setting and participants</i>: 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. <b><i>Results:</i></b> High-risk women had a significantly higher prevalence of a short cervix, defined as either ≤25 mm (4.4% vs. 2.2%; <i>p</i> &#x3c; 0.0001) or ≤20 mm (2.4% vs. 1.2%; <i>p</i> &#x3c; 0.0001) but not for ≤15 mm (1.2% vs. 0.9%; <i>p</i> &#x3c; 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; <i>p</i> &#x3c; 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%; <i>p</i> &#x3c; 0.0001), ≤20 mm (2.4% vs. 0.98%; <i>p</i> &#x3c; 0.0001), and ≤15 mm (1.6% vs. 0.7%; <i>p</i> &#x3c; 0.0001) than low-risk women scanned between 18 and 21 weeks of gestation. Similar results were observed for high-risk women. <b><i>Limitations:</i></b> No gestational age at delivery was evaluated. <b><i>Conclusion:</i></b> 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.