Prolonged acetaminophen use (1 week) by pregnant women may suppress fetal testosterone production, according to researchers from the University of Edinburgh. Findings from the study are published in Science Translational Medicine.

Previous studies have shown that prolonged use of acetaminophen increases the risk of cryptorchidism in unborn baby boys, but its effects on fetal testosterone production have not been studied. In this study, scientists used a xenograft model to expose human fetal testes to clinically relevant doses of acetaminophen. These grafts have been shown to mimic how the developing testes grow and function during pregnancy.

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Exposure to acetaminophen at a therapeutic dose for 7 days significantly reduced plasma testosterone by 45% (P=0.025) and seminal vesicle weight by 18% (P=0.005) in castrate host mice bearing human fetal testis xenografts. Acetaminophen exposure for just 24 hours, however, did not result in a change of either plasma testosterone or seminal vesicle weight.

Researchers recommend that pregnant women should follow guidelines in taking acetaminophen at the lowest effective dose for the shortest duration. More studies are needed to define the dose-response and treatment duration relationships to establish the maximum dose and period without the adverse effect.  

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