Three children with thrombopenia and radial aplasia were examined at the Centre de Génétique Médicale of Marsielles from 1974 to 1976. In each case the genetic basis of the anomaly was discussed with the family at genetic counseling underlining the high risk of recurrence related to the autosomal recessive transmission. Each proband was the only child of the couple. In the first case the father and mother, each having one child from a previous marriage, decided to have no more children. In the second case, the use of fetoscopy and its limitations were discussed as another pregnancy was desired. However, the parents finally refused the procedure during pregnancy which yielded a second child with phocomelia who did not survive. In the third and most recent case the proband died. Since the young couple strongly desired another child, ultrasonic monitoring of pregnancy was cautiously suggested and its limitations clearly exposed. Echography was regularly repeated from the third month of pregnancy. The forearms were never detected on echography, nor on fetal radiography. Pregnancy was thus interrupted with prostaglandins at 21 weeks gestational age. On examination the fetus presented bilateral aplasia of the forearm. Based on these observations, the authors discuss the problems raised by prenatal diagnosis of upper limb malformations.