Kharbanda EO, et al. - The risk of spontaneous abortion after quadrivalent human papillomavirus (4vHPV) vaccination before and during pregnancy was investigated across seven integrated health systems within the Vaccine Safety Datalink. Inadvertent 4vHPV exposure during or peripregnancy was not significantly associated with an increased risk of spontaneous abortion.

Methods

• Researchers performed a retrospective observational cohort study comparing risks for spontaneous abortion after 4vHPV in three exposure windows : distal (16–22 weeks before the last menstrual period [LMP]), peripregnancy (within 6 weeks before the LMP), and during pregnancy (LMP through 19 weeks of gestation).
• They included women 12–27 years of age with a pregnancy between 2008 and 2014, with continuous insurance enrollment 8 months before and through pregnancy end, and with a live birth, stillbirth, or spontaneous abortion.
• Using validated algorithms, they identified pregnancies.
• Verification of spontaneous abortions and stillbirths was performed by chart review with spontaneous abortions adjudicated by clinical experts.
• Multiple gestations, spontaneous abortions before 6 weeks of gestation, and women using medications increasing risk of spontaneous abortion were excluded.
• Using time-dependent covariate Cox models, they compared spontaneous abortion risk after 4vHPV during pregnancy with distal vaccination.
• Using standard Cox models, they evaluated spontaneous abortion risk for peripregnancy compared with distal vaccination.

Results

• In specified risk windows, 2,800 pregnancies with 4vHPV exposure were identified: 919 (33%) distal, 986 (35%) peripregnancy, and 895 (32%) during pregnancy.
• Distal and peripregnancy groups had mean age of 22.4 years compared with 21.4 years among women vaccinated during pregnancy.
• Among women with distal 4vHPV exposure, a spontaneous abortion was reported in 96 (10.4%) women.
• Spontaneous abortions occurred in 110 (11.2%) and 77 (8.6%) among women with peripregnancy and during pregnancy exposures, respectively.
• No increase in the risk of spontaneous abortion was evident among women who received 4vHPV during pregnancy (adjusted hazard ratio 1.10, 95% CI 0.81–1.51) or peripregnancy 1.07 (0.81–1.41).