Which group of medications is contraindicated in pregnancy?

ACE inhibitors are contraindicated in pregnancy due to their association with serious fetal complications, particularly in the second and third trimesters. They can cause significant harm, including fetal hypotension, renal failure, and even death. Exposure to ACE inhibitors during pregnancy is particularly concerning as they can affect the development of the fetal kidneys and lead to oligohydramnios (low amniotic fluid), which poses risks for pulmonary and skeletal development.

In contrast, while beta blockers and calcium channel blockers are used cautiously in pregnancy, they are not completely contraindicated; certain ones may be prescribed if absolutely necessary. Antihistamines can be used during pregnancy, particularly those with established safety records. Therefore, ACE inhibitors are uniquely recognized for their potential to cause serious adverse effects during pregnancy, making them the group of medications that should be avoided.