A Comparison of Vaginal and Intramuscular Progesterone for the Prevention of Recurrent Preterm Birth.

OBJECTIVE: This study aimed to examine whether vaginal progesterone is noninferior to 17-α hydroxyprogesterone caproate (17OHP-C) in the prevention of recurrent preterm birth (PTB). STUDY DESIGN: This retrospective cohort study included singleton pregnancies among women with a history of spontaneous PTB who received prenatal care at a single tertiary center from 2011 to 2016. Pregnancies were excluded if progesterone was not initiated prior to 24 weeks or the fetus had a major congenital anomaly. The primary outcome was PTB <37 weeks. A priori, noninferiority was to be established if the upper bound of the adjusted two-sided 90% confidence interval (CI) for the difference in PTB fell below 9%. Inverse probability of treatment weighting (IPTW) was used to carefully control for confounding associated with choice of treatment and PTB. Adjusted differences in PTB proportions were estimated via IPTW regression, with standard errors adjustment for multiple pregnancies per woman. Secondary outcomes included PTB <34 and <28 weeks, spontaneous PTB, neonatal intensive care unit admission, and gestational age at delivery. RESULTS: Among 858 pregnancies, 41% (n = 353) received vaginal progesterone and 59% (n = 505) were given 17OHP-C. Vaginal progesterone use was more common later in the study period, and among women who established prenatal care later, had prior PTBs at later gestational ages, and whose race/ethnicity was neither non-Hispanic white nor non-Hispanic Black. Vaginal progesterone did not meet noninferiority criteria compared with 17-OHPC in examining PTB <37 weeks, with an IPTW adjusted difference of 3.4% (90% CI: -3.5, 10.3). For secondary outcomes, IPTW adjusted differences between treatment groups were generally small and CIs were wide. CONCLUSION: We could not conclude noninferiority of vaginal progesterone to 17OHP-C; however, women and providers may be willing to accept a larger difference (>9%) when considering the cost and availability of vaginal progesterone versus 17OHP-C. A well-designed randomized trial is needed. KEY POINTS: · Vaginal progesterone is not noninferior to 17OHP-C.. · PTB risk may be 10% higher with vaginal progesterone.. · Associations did not differ based on obesity status..

Optimal antenatal corticosteroid exposure in women with history of preterm birth and asymptomatic short cervical length.

BACKGROUND: A proposed benefit of cervical length assessment after 24 weeks' gestation in women with a history of preterm birth is to aid in the timing of antenatal corticosteroids in otherwise asymptomatic women. OBJECTIVE: We sought to investigate whether the use of an ultrasonographic short cervical length as an indication for antenatal corticosteroids in asymptomatic women results in optimal exposure compared with women receiving antenatal corticosteroids for preterm labor symptoms. STUDY DESIGN: Retrospective cohort study of all women with a previous spontaneous preterm birth and a singleton gestation who underwent serial cervical length assessment at a large academic tertiary medical center from 2011 to 2016. Patients were included in the analysis if they received antenatal corticosteroids for either an asymptomatic short cervical length or symptoms of preterm labor. The primary outcome was optimal antenatal corticosteroids exposure (latency to delivery of ≤7 days). PROPOSED CHANGE IN RESULTS: Poisson regression with robust error variance was used to calculate incidence rate ratios (IRR) and confidence intervals (CI) for primary and secondary outcomes adjusting for primary and secondary outcomes adjusting for race, earliest previous preterm birth, and current cerclage. RESULTS: There were 287 women meeting inclusion criteria, among whom 166 (57.8%) received antenatal corticosteroids for a short cervical length and 121 (42.2%) for preterm labor symptoms. Women who received antenatal corticosteroids for a short cervical length were less likely to have optimal exposure (1.2% vs 19.0%; incidence rate ratios, 0.06; confidence interval, 0.02-0.27) compared with women with preterm labor symptoms. They were also more likely to have exposure with eventual term delivery (43.2% vs 33.4%; incidence rate ratios, 1.6; confidence interval, 1.2-2.0). Importantly, women who received antenatal corticosteroids for a short cervical length were significantly less likely to receive either an initial or rescue antenatal corticosteroids course within 7 days of a preterm delivery of less than 34 weeks' gestation (42.9% vs 76.9%; incidence rate ratios, 0.52; confidence interval, 0.35-0.75). CONCLUSION: Women with a previous preterm birth who receive antenatal corticosteroids for an asymptomatic short cervical length are less likely to have optimal exposure than women with symptoms of preterm labor. These data challenge the practice of cervical length surveillance for the sole indication of timing antenatal corticosteroids administration.