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Updated: Apr 15, 2026

Ex vivo Culture of Human Placental Explants for the Study of Viral Transmission Across the Maternal-Fetal Interface
Published on: December 30, 2025
Final report on exposure during pregnancy from a pregnancy registry for quadrivalent human papillomavirus vaccine
Mary Ann Goss1, Fabio Lievano1, Karyn M Buchanan1
1Merck Research Laboratories, West Point, PA, USA.
Objective:
To better describe the safety profile of pregnancy exposures to the qHPV vaccine by acquiring and analyzing post-marketing data on pregnancy outcomes.
Methods:
This is a voluntary, post-marketing prenatal vaccine exposure registry. Enrollment criteria included an identifiable patient and health care provider from the United States, France, or Canada and exposure within 1 month before the date of onset of the last menstrual period or at any time during pregnancy. Outcomes of interest were pregnancy outcomes and birth defects. Prospectively reported cases were used for rate calculations.
Results:
For the 1752 prospective reports with known outcome, 1518 (86.6%) were live births, including ten twin pregnancies. Of 1527 neonates, 1444 (94.6%) had no congenital anomalies. The overall rate of spontaneous abortion was 6.7 per 100 outcomes (95% confidence interval [CI] 5.5-8.2). The prevalence of major birth defects was 2.4 per 100 live-born neonates (95% CI 1.7-3.3). There were 12 fetal deaths (0.8 per 100 outcomes, 95% CI 0.4-1.4).
Conclusion:
Rates of spontaneous abortions and major birth defects were not greater than the general population rates. Although no adverse signals have been identified to date, the qHPV vaccine is not recommended for use in pregnant women.
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