During which time frame are ACE inhibitors most critical in terms of teratogenic effects?

The critical period for teratogenic effects associated with ACE inhibitors is during the second and third trimesters of pregnancy. During this time, exposure to these medications can lead to significant fetal risks, especially related to renal function and development.

In the latter stages of pregnancy, ACE inhibitors can cause complications such as oligohydramnios (low amniotic fluid) due to fetal kidney dysfunction, which can further lead to pulmonary hypoplasia and other developmental issues. Additionally, there is a risk of neonatal hypotension and renal impairment after delivery.

While the first trimester is an important time for many teratogenic effects, certain medications, including ACE inhibitors, are particularly concerning in the later stages when their influence on vascular and renal systems can pose additional risks to the developing fetus. This specific timing highlights the need for careful management of medications during late pregnancy to mitigate the potential adverse effects on the fetus.