How many US obstetrical trials reach publication? A cross-sectional analysis of and PubMed from 2007 to 2019


      Obstetrical clinical trials are the foundation of evidence-based medicine during pregnancy. As more obstetrical trials are conducted, understanding the publication characteristics of these trials is of utmost importance to advance obstetrical health.


      This study aimed to characterize the frequency of publication and trial characteristics associated with publication among obstetrical clinical trials in the United States. We additionally sought to examine time from trial completion to publication.


      This was a cross-sectional analysis of completed obstetrical trials with an intervention design and at least 1 site in the United States registered to from 2007 to 2019. Trial characteristics were cross-referenced with PubMed to determine publication status up to 2021 using the National Clinical Trial identification number. Bivariable analyses were conducted to determine trial characteristics associated with publication. Multivariable logistic regression models controlling for prespecified covariates were generated to estimate the relationship between funding, primary purpose, and therapeutic foci with publication. Additional exploratory analyses of other trial characteristics were conducted. Time to publication was analyzed using Kaplan–Meier curves and Cox regression models.


      Of the 1879 obstetrical trials with registered completion, a total of 575 (30.6%) had at least 1 site in the United States, were completed before October 1, 2019, and were included in this analysis. Between October 2007 and October 2019, fewer than two-thirds (N=348, 60.5%) of trials reached publication. Annual rates of publication ranged from 46.4% in 2018 to 70.0% in 2007. No difference was observed in publication by funding, primary purpose, or therapeutic foci (all P>.05). Trials with characteristics indicating high trial quality—including randomized allocation scheme, ≥50 participants enrolled, ≥2 sites, and presence of a data safety monitoring committee—had increased odds of publication compared with those without such characteristics (all P<.05). For example, studies with randomized allocation of intervention had 2-fold greater odds of publication than nonrandomized studies (adjusted odds ratio, 2.09; 95% confidence interval, 1.30–3.37). Studies with ≥150 participants had nearly 8-fold odds of publication (adjusted odds ratio, 7.90; 95% confidence interval, 3.78–17.49) relative to studies with <50 participants. Temporal analysis demonstrated variability in time to publication among obstetrical trials, with a median time of 20.1 months after trial completion, and with most trials that reached publication having been published by 40 months. No difference was observed in time to publication by funding, primary purpose, or therapeutic foci (all P>.05).


      Publication of obstetrical trials remains suboptimal, with significant differences observed between trials with indicators of high quality and those without. Most trials that reach publication are published within 2 years of registered completion on


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