Background Dextromethorphan (DM), the d-isomer of thecodeine analog levorphanol, is an active ingredient present in avariety of cough and cold remedies. Recently, data generated from astudy in chick embryos were extrapolated to suggest that pregnant womenshould not use this drug because of the risk of birth defects. Weconducted a controlled study of pregnant women who used DM, to examinethe possible teratogenic risk in humans. Materials andmethods We followed up women who used DM and had been counseledby the Motherisk Program during their pregnancy. A control group ofwomen was matched for age, smoking, alcohol use, and disease state(upper respiratory tract infection, not treated with DM). Results We were able to ascertain pregnancy outcomein 184 women. There were 172 live births, 10 spontaneous abortions, 1therapeutic abortion, and 1 stillbirth. One hundred twenty-eight of thewomen used the drug during the first trimester of pregnancy. There werethree major malformations (2.3%) among the babies of women who used DMin the first trimester, seven minor malformations, and the mean(± SD) birth weight was 3,381 ± 670 g. In the controlgroup, there were 174 live births, 8 spontaneous abortions, and 2therapeutic abortions. There were five major malformations, one ofwhich was a chromosomal abnormality (2.8%), eight minor malformations, and the mean birth weight was 3,446 ± 571 g. Conclusion This study fails to show that DM use duringpregnancy increases the rates of major malformations above the expectedbaseline rate of 1% to 3%.