Teratological and radiocephalometric analysis of craniofacial malformations induced with retinoic acid in rhesus monkeys Macaca mulatta

Fifteen pregnant Macaca mulatta were treated with doses of 20 or 40 mg of retinoic acid between 19–45 or 17–45 days of gestation, respectively, for 4–8 consecutive days. Based on gross examination, ten malformed infants, including one stillbirth and one abortus, four normal infants, and one resorption were produced. The most critical sensitive period was between days 24–35 of gestation, and the malformations primarily involved the craniofacial skeleton. Ten treated infants and eight age‐matched controls were cephalometrically analyzed using craniometric points as closely correlated as possible with those in humans in order to define the craniofacial malformations induced prenatally by retinoic acid. Although all ten animals had detectable linear and angular deviations from the controls, four had cephalometric patterns which appeared to be of similar developmental origin.