Taking ACE inhibitors during early pregnancy: is it safe?

QUESTION: I knew that angiotensin-converting enzyme (ACE) inhibitors were risky to use during late pregnancy because they can cause renal shutdown in the fetus. Recently I heard of a study that claimed first-trimester exposure (when many patients still are unaware of their pregnancies) can also cause major malformations. Is this proven? ANSWER: A recent study did suggest an increased risk of malformations after first-trimester exposure to ACE inhibitors among women treated for hypertension. We believe this study had serious limitations that preclude drawing any conclusions at present.