Retinoic acid, an analogue of vitamin A, is known to be teratogenic in laboratory animals and has recently been implicated in a few clinical case reports. To study the human teratogenicity of this agent, we investigated 154 human pregnancies with fetal exposure to isotretinoin, a retinoid prescribed for severe recalcitrant cystic acne. The outcomes were 95 elective abortions, 26 infants without major malformations, 12 spontaneous abortions, and 21 malformed infants. A subset of 36 of the 154 pregnancies was observed prospectively. The outcomes in this cohort were 8 spontaneous abortions, 23 normal infants, and 5 malformed infants. Exposure to isotretinoin was associated with an unusually high relative risk for a group of selected major malformations (relative risk = 25.6; 95 per cent confidence interval, 11.4 to 57.5). Among the 21 malformed infants we found a characteristic pattern of malformation involving craniofacial, cardiac, thymic, and central nervous system structures. The malformations included microtia/anotia (15 infants), micrognathia (6), cleft palate (3), conotruncal heart defects and aortic-arch abnormalities (8), thymic defects (7), retinal or optic-nerve abnormalities (4), and central nervous system malformations (18). The pattern of malformation closely resembled that produced in animal studies of retinoid teratogenesis. It is possible that a major mechanism of isotretinoin teratogenesis is a deleterious effect on cephalic neural-crest cell activity that results in the observed craniofacial, cardiac, and thymic malformations.

Estimates of the Apert syndrome birth prevalence and the mutation rate are reported for Washington State, Nebraska, Denmark, Italy, Spain, Atlanta, and Northern California. Data were pooled to increase the number of Apert births (n = 57) and produce a more stable birth prevalence estimate. Birth prevalence of the Apert syndrome was calculated to be approximately 15.5/1,000,000 births, which is twice the rate determined in earlier studies. The major reason appears to be incomplete ascertainment in the earlier studies. The similarity of the point estimates and the narrow bounds of the confidence limits in the present study suggest that the birth prevalence of the Apert syndrome over different populations is fairly uniform. The mutation rate was calculated to be 7.8 x 10(-6) per gene per generation. Apert syndrome accounts for about 4.5% of all cases of craniosynostosis. The mortality rate appears to be increased compared to that experienced in the general population; however, further study of the problem is necessary.

Valproic acid use during pregnancy results in an absolute risk for spina bifida of 1-2%. This increased risk is comparable to the recurrence risk for neural tube defects and warrants informed counselling and access to prenatal diagnosis. There is no substantial evidence that valproic acid use increases the risk for other specific major malformations above the increased risk due to maternal epilepsy. Valproic acid may cause a characteristic pattern of minor facial malformations. Further definition and confirmation are required, and the magnitude of the risk needs to be determined. There are inadequate data to assess the magnitude, if any, of the risks for postnatal growth abnormalities and developmental disabilities associated with the use of valproic acid during pregnancy. Birth-defect monitoring programs and international collaboration among the staffs of monitoring programs played a major role in determining that valproic acid is a human teratogen.