indomethacin for preterm labor fetal toxicity in a dizygotic twin gestation indomethacin was given for the treatment of preterm labor in a twin pregnancy at a dosage of 200 mgday for 7 days beginning at 34 weeks and 5 days gestation during treatment one twin developed closure of the ductus arteriosus tricuspid regurgitation right ventricular dysfunction and pericardial effusion severe oligohydramnios in both amniotic sacs appeared as well all findings resolved within 7 days of discontinuation of the medication the infants delivered vaginally at 37 weeks gestation were alive and well at a 2month followup visit we believe that all fetuses of mothers treated with indomethacin should be closely monitored for early evidence of decreased amniotic fluid volume and constriction of the ductus arteriosus