Drug	Possible effect
Angiotensin converting enzyme inhibitors19	Fetal or neonatal renal failure
Antithyroid drugs20	Fetal hypothyroidism (if drug used in excessive dose)
Benzodiazepines21	Drug dependence in the fetus
β blockers16	Growth retardation may occur if used throughout pregnancy (this has been shown for atenolol and inferred for others)
Barbiturates22	Drug dependence in the fetus
Non-steroidal anti-inflammatory drugs23	Constriction of ductus arteriosus (from second trimester onwards)
Tetracyclines17	Tooth discoloration; may inhibit bone growth (brief exposure early in first trimester not shown to be harmful)
Warfarin24	Bleeding into fetal brain (even if the mother’s international normalised ratio is therapeutic)