Medication Use in Pregnancy: Contraindications and Risks

Category X Medications (Absolutely Contraindicated)

Sodium valproate is a known teratogen that must not be used during pregnancy, causing neural tube defects and other major congenital malformations, and is contraindicated in females of childbearing potential, according to the American Academy of Neurology 1

ACE inhibitors are contraindicated in the second and third trimesters due to the risk of oligohydramnios, permanent fetal renal damage, and should only be considered for active scleroderma renal crisis where maternal benefit outweighs fetal risk, as recommended by the American College of Rheumatology 2
Azathioprine is teratogenic in animals but appears relatively safe in humans with careful monitoring, and is classified as category D, with benefits and risks requiring detailed discussion with the patient, according to the European Association for the Study of the Liver 3

Topiramate is contraindicated during pregnancy due to its association with adverse fetal effects, and is also contraindicated in nephrolithiasis, lactation, and glaucoma, as recommended by the American Academy of Neurology 1
Candesartan, an angiotensin II-receptor blocker, is contraindicated in pregnancy due to adverse fetal effects, with a similar mechanism of harm as ACE inhibitors, according to the American Heart Association 1
High-dose corticosteroids in the first trimester increase the risk of cleft palate, adrenal insufficiency in newborns, and premature rupture of membranes, and require specialist supervision, as recommended by the European Association for the Study of the Liver 3

ACE inhibitors become contraindicated specifically during the second and third trimesters, with a different risk profile and concerns shifting to functional abnormalities rather than structural defects, as recommended by the American College of Rheumatology 2

Abrupt discontinuation of medications for chronic conditions should be avoided without medical supervision, as uncontrolled maternal disease can harm the fetus more than appropriate medication use, according to the European Respiratory Society 4

Lithium poses significant teratogenic risk and must be stopped immediately, particularly in the first trimester when organogenesis occurs, due to risk of cardiac malformations and other congenital defects, according to the American College of Obstetricians and Gynecologists 5, 6
Atenolol should never be used in pregnancy due to pronounced growth restriction effects, as recommended by the European Society of Cardiology 7, 5

Metoprolol is considered safe during pregnancy and is recommended for ongoing management of arrhythmias and hypertension, with close monitoring of fetal growth and surveillance for fetal bradycardia, by the American Heart Association 8, 9, 7
Acetaminophen remains the safest pain and fever medication during pregnancy and can be continued when medically needed, at the lowest effective dose, for the shortest possible duration, according to the American Academy of Pediatrics 10, 6

The first trimester, particularly during organogenesis (weeks 3-8), is the critical period when medications pose the highest risk for structural birth defects, as stated by the National Institute of Child Health and Human Development 6, 7

Serial echocardiography monitoring, particularly during second and third trimesters, and fetal growth monitoring due to metoprolol use, are recommended by the American College of Cardiology 9
Blood pressure monitoring with a target of 110-135/85 mmHg, and monitoring for fetal bradycardia if continuing metoprolol, are advised by the American Heart Association 5, 9

The American Diabetes Association recommends that medications such as warfarin, isotretinoin, sodium valproate, ACE inhibitors, angiotensin receptor blockers (ARBs), statins, and all weight-loss medications are absolutely contraindicated in pregnancy and must be avoided in women who are or may become pregnant 11

ACE inhibitors are absolutely contraindicated in pregnancy, particularly in the second and third trimesters, causing fetal renal dysplasia, oligohydramnios, pulmonary hypoplasia, and intrauterine growth restriction, as recommended by the American Academy of Pediatrics 11, 12
Angiotensin receptor blockers (ARBs) are absolutely contraindicated in pregnancy with similar mechanisms of harm as ACE inhibitors, as recommended by the American Academy of Pediatrics 11, 12
Statins should be avoided in pregnancy and must be stopped at conception in sexually active women of childbearing age not using reliable contraception, as recommended by the American Diabetes Association 11

All weight-loss medications, including phentermine, orlistat, lorcaserin, phentermine/topiramate, naltrexone/bupropion, and liraglutide 3.0 mg, are absolutely contraindicated in women who are or may become pregnant, as recommended by the American Diabetes Association 13

Women of childbearing age taking any of these medications must use reliable contraception, as recommended by the American Diabetes Association 11, 13
ACE inhibitors, ARBs, and statins should be stopped at conception in sexually active women not using reliable contraception, as recommended by the American Diabetes Association 11