Tylenol can cross the placenta, making its way to the developing fetus and its nervous system. The drug is known to be an endocrine disruptor, and has been linked to undescended testes in males. With the maternal hormone environment playing a critical role in fetal development, authors of the study in JAMA Pediatrics journal say that it’s possible that acetaminophen may interrupt brain development by interfering with maternal hormones or via neurotoxicity such as the induction of oxidative stress that can cause neuronal death.