Angiotensin converting enzyme (ACE) inhibitors and angiotensin II (AT-II)-receptor-antagonists have been demonstrated to cause fetotoxicity when administered to women during the second and third trimester of pregnancy. Although use of ACE inhibitors during the first trimester of pregnancy seems to be safe, with no associated teratogenicity, there is not sufficient information regarding the safety of first-trimester exposure to AT-II-receptor-antagonists. We report a case of exencephaly and unilateral renal agenesia in a fetus of a diabetic woman who became pregnant while taking irbesartan.