Oral methyldopa has been assigned to pregnancy category B and the intravenous form methyldopate hydrochloride (the ethyl ester of methyldopa) has been assigned to category C by the FDA. Animal studies have failed to reveal evidence of teratogenicity or fetotoxicity. There are no controlled data in human pregnancy. Methyldopa is only recommended for use during pregnancy when benefit outweighs risk.

Methyldopa crosses the placenta, and may cause mild hypotension in neonates of treated mothers. Because it has been safely and successfully used to treat hypertension during pregnancy, some experts consider it to be the drug of choice for the treatment of nonemergent hypertension during pregnancy.

Of 3,248 children with any malformation related to a diuretic or a drug taken for a cardiovascular disorder from a population of 50,282 mother-child pairs in the Collaborative Perinatal Project, only one case associated with methyldopa was monitored, and no abnormalities were observed. An infant born with congenital heart disease, esophageal atresia, an absent kidney, and hypospadias whose mother received methyldopa throughout her pregnancy and clomiphene in the first trimester has been reported.

In one study a decrease in mean head circumference of 202 neonates of mothers who were begun on methyldopa during gestation weeks 16 and 20 has been reported. Long-term follow-up of 98% of these children has not revealed abnormalities, and the development delay commonly seen in children of hypertensive mothers was less in children whose mothers received methyldopa than in children of untreated mothers.

A review of 1,157 hypertensive pregnancies has revealed no evidence of teratogenicity or fetotoxicity associated with methyldopa.

The Michigan Medicaid surveillance study showed no association between the use of methyldopa and congenital defects (written communication, Franz Rosa, MD, Food and Drug Administration, 1994). This report is a summary of information from two studies, one in which 120 of 104,000 pregnant women from 1980 to 1983, and one in which 242 of 229,101 pregnant women from 1985 to 1992 received methyldopa during pregnancy. Eight and 11 total defects were observed in these studies, respectively (8 and 10 were expected, respectively). The one instance each of cardiovascular defect, cleft palate, and polydactyly in the second study did not achieve statistical significance. These data do not support an association between methyldopa and congenital defects.

The various features of the fetal heart rate pattern, as evaluated in a controlled trial by computerized cardiotocography in human pregnancy, were not influenced by methyldopa 250 mg three times a day in 19 women with preeclampsia.

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Limited data from four nursing women who were taking methyldopa 750 to 2,000 mg per day revealed milk concentrations ranging from 0.1 to 0.9 mcg per mL.

Methyldopa is excreted into human milk. Adverse effects in the nursing infant are unlikely. The manufacturer recommends that caution be used when administering methyldopa to nursing women.

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