(1020) Risk of spontaneous PTB < 34 weeks among women with mid-trimester cervical length >25 mm

Friday, January 31, 2025

4:00 PM – 6:00 PM

Submitting Author and Presenting Author(s)

Edgar A. Hernandez-Andrade, MD, PhD (he/him/his)

Professor
McGovern Medical School at UTHealth Houston
Houston, Texas, United States

Coauthor(s)

DG

Donatella Gerulewicz Vannini

University of Texas Health Science Center in Houston, McGovern Medical School
Houston, Texas, United States
ES

Eleazar E. Soto, MD

Assistant Professor
McGovern Medical School at UTHealth Houston
Houston, Texas, United States
Sean C. Blackwell, MD

Professor and Chair
McGovern Medical School at UTHealth Houston
Houston, Texas, United States

Objective: There is a general assumption that the longer the cervix the lower the rate of spontaneous preterm birth (SPTB). This study aimed to test this hypothesis in low-risk and high-risk pregnant women with normal cervical length.

Study Design: Transvaginal cervical length (TVCL) was measured in 3,376 singleton pregnancies with no fetal anomalies at 17-24 weeks of gestation. Patients were grouped as low (LR) and high risk (HR) based on history of SPTB. TVCL measurements were analyzed as < 15 mm and < 25 mm, and then in groups of 5 mm from 25- 55 mm. SPTB was considered as ≤ 34 weeks of gestation not due to maternal or fetal indication such as placenta accreta, preeclampsia, or fetal growth restriction. Differences in the prevalence of SPTB among the CL groups and between LR and HR patients were evaluated.

Results: 2,863 (84.9%) patients were considered LR, and 513 (15.1%) HR. Short cervix ( ≤ 25 mm) was found in 3.0% of women (n=103; LR n=82 (2.8%); HR n=21 (4.1%)). Prevalence of SPTB was 6.6% (n=189; LR 4.0% n=115, HR 14.4% n=74; p< 0.001). Figure 1 shows the prevalence of SPTB ≤ 34 weeks according to the TVCL groups in LR and HR patients. The prevalence of SPTB was significantly higher in HR patients at any TVCL group than for LR patients. Among LR women, the risk of SPTB did not significantly change when TVCL was ≥ 30 mm, yet LR patients with TVCL between 25.1 and 30.0 mm had a higher risk of SPTB ≤ 34 weeks as compared to those with TVCL > 30.1 mm (p=0.02). In HR patients the prevalence of SPTB did not significantly change when TVLC was >25 mm.

Conclusion: In our population, the risk of SPTB ≤ 34 weeks does not substantively increase once TVCL ≥ 30 mm for LR women and once > 25 mm in HR women. HR women had almost 3 times higher rate of SPTB than LR patients at any TVCL cut-off.