Flexeril Oral: Uses, Side Effects, Interactions, Pictures, Warnings & Dosing Most vital organs form between 3 and 8 weeks gestation, so exposures that occur during this time have the potential to cause significant structural malformations. Exposures later in pregnancy may have a greater impact on fetal growth. Medication use near term can also impact the neonate following delivery. For example, maternal use of opioid analgesics near term can cause respiratory depression in the neonate and …