Use of antiviral medications during pregnancy and the likelihood of preeclampsia in a population-based register study.

Viral infections and reactivations have been linked to several pregnancy complications. Antiviral medications are often prescribed as a prophylactic measure to prevent infant infection. This study examines associations between antiviral medication use during pregnancy and preeclampsia, thereby exploring links between viruses and such pregnancy complication. We analyzed data from 618,814 first-time mothers in Sweden (2007-2019) using four national registers. Of these 27,135 (4.4%) developed preeclampsia and 18,004 (2.9%) filled an antiviral medication prescription. Adjusted logistic regression with inverse probability of treatment weighting was used to evaluate associations between use of antiviral medication and preeclampsia. Antiviral medication use was associated with a reduced likelihood of preeclampsia (aOR 0.88; 95% CI, 0.81-0.96). Particularly, antiviral medication use was associated with a reduced likelihood of developing preeclampsia with delivery before 34 weeks gestation (aOR 0.66; 95% CI, 0.48-0.92) and preeclampsia with a small for gestational age infant (aOR, 0.74; 95% CI, 0.57-0.96). Timing of antiviral prescription filling was also investigated. Antiviral medication use in the third trimester was associated with a reduced likelihood of preeclampsia (aOR 0.77; 95% CI, 0.67-0.90), but not when used during the first two trimesters. Our study suggests that viral infections or reactivation might play a role in the etiology of preeclampsia, highlighting the need to further explore viral infections' role in preeclampsia development.