(429) Does Vaginal Progesterone prevent preterm birth in women with shortened cervix after 24 weeks?

To determine the association of vaginal progesterone treatment and the risk of spontaneous preterm birth (sPTB) in women with a short cervix diagnosed at 24-34 weeks of gestation.

Study Design:

A retrospective cohort study in a single university affiliated medical center with approximately 12,500 annual deliveries (2011-2022). Women with a singleton pregnancy and a newly diagnosed short cervix (≤25mm) at 24+0-33+6 weeks who were given vaginal progesterone were compared to those that were not treated. The initiation of progesterone treatment was based on physician's preference and continued until 36 weeks. Severe short cervix was defined as cervical length (CL) ≤15 mm. Exclusion criteria were: prior progesterone or tocolysis usage, cerclage and previous PTB. The primary outcome was sPTB < 37 weeks of GA.

Results:

1.   Overall, 862 women were eligible for analysis, among them 471 (54.6%) women were treated with vaginal progesterone and 391 (45.4%) did not. 183 women (21.2%) were diagnosed with CL≤15mm.

2.   There was no significant difference between the groups in the rate of sPTB at < 37 weeks (29.4% vs.33.5%, p=0.19), 34 weeks (8.7% vs 12.1%, p=0.11) and 32 weeks (4.9% vs 7%, p=0.19).  

3.   No significant differences were found in background characteristics. Women in the progesterone group were diagnosed earlier (29.5 ± 2.7 vs. 31.5 ± 2.3, weeks P< 0.001), had a shorter CL at diagnosis (17.5 ± 5.3 Vs 19.6 ± 5 mm, P< 0.001), and higher rate of CL≤15 mm (25.9% vs 15.6%, P=0.01).  

4.   Progesterone treatment was associated with a longer interval from diagnosis to delivery, in women with CL≤ 25mm and CL≤15mm as comparted to no treatment [Mean time of 54 ± 27 vs. 41.8 ± 23.5 days, and 52.6 ± 29.5 vs 33.2 ± 27 days, respectively. (P< 0.001)]. Hazard Ratio of 1.9, 95% CI [1.7-2.3], and 2.2, 95% CI [1.4-3.3], respectively. (Figure).

Conclusion:

Vaginal progesterone given to women with a short cervix at 24-34 weeks of GA is associated with mean prolongation of pregnancy of 12-19 days, with not significant impact on the rate of sPTB.