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CME Credit Offered
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Abstract Award
Recording available 2/16-5/2
Recording available 2/16-5/2
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AIUM Credit
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Foundation Awardee
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Abstract Award
Abstract Award
Foundation Awardee
Foundation Awardee

Poster Session 2

Category: Epidemiology

Poster Session 2

(462) Incidence of Recurrent Preterm Birth Before and After the PROLONG Trial

Wednesday, February 11, 2026
3:30 PM - 5:00 PM  
Objective:
After its initial FDA approval in 2011, 17-hydroxyprogesterone (17-OH-P) was prescribed to patients with a history of spontaneous preterm birth (PTB) to reduce the risk of recurrence. In the confirmatory PROLONG trial, 17-OH-P did not decrease recurrent PTB. In a contemporary, US-based cohort, our objective was to assess if the PROLONG trial changed 17-OH-P prescribing practices and to compare the rates of PTB before and after the trial.

Study Design:
We performed a pre-post analysis of singleton patients with a history of PTB receiving care within a single, large health care system between July 1, 2016, and February 28, 2023. Pregnancies at 20 weeks between October 2019 and September 2020 were excluded to allow for any potential practice changes to take effect; this also excluded pregnancies delivered during the height of the COVID-19 pandemic. The primary outcomes were 17-OH-P use and PTB < 35 weeks. Secondary outcomes were PTB < 32 weeks and PTB < 37 weeks. Chi-square tests and logistic regression were used, adjusting for maternal age, race, ethnicity, insurance, and number of prior PTBs.

Results:
1719 patients in the pre-group and 1780 in the post-group were included. 17-OH-P use decreased from 23.6% to 5.7% between the two periods (p< 0.001). There was no significant difference in rates of PTB between the time periods (< 35 weeks: 10.2 vs 10.7%, p=0.64; < 32 weeks: 4.1 vs. 3.8%, p=0.70; < 37 weeks: 23.2 vs. 24.5%, p=0.37). In the logistic regression model, there was no significantly increased risk of preterm birth for delivering after the PROLONG trial compared to before (adjusted odds ratio for PTB< 32 weeks for delivering in the post vs. pre-PROLONG period: 1.00 (0.80-1.26)), despite the notable change in 17-OH-P use.

Conclusion:
Within a single health system, 17-OH-P use dropped by >75% after the PROLONG trial with no measurable changes in PTB rates. These findings support the conclusions of the PROLONG trial, though additional confirmatory research with larger sample sizes to investigate for potential differential effects among population subgroups.