An analysis of 28 dysmorphic offspring with a retrospectively ascertained history of maternal hyperthermia during the first trimester of pregnancy showed a similarity in their pattern of CNS dysfunction and facial dysmorphogenesis. All survivors had mental deficiency and most of them demonstrated altered muscle tone, including hypotonia with increased deep tendon reflexes. Those exposed at four to seven weeks' gestation showed an increased prevalance of facial dysmorphogenesis. The duration of the high fever was usually one or more days, an unusual occurrence during the first trimester of pregnancy. The nature of these defects in relation to the relative timing of hyperthermia exposure is similar to that previously noted in animal studies. The morphogenetic implications of these findings are explored and the need for larger, controlled studies is suggested.

Pleet, H., Graham, J. M., & Smith, D. W. (1981). Central Nervous System and Facial Defects Associated with Maternal Hyperthermia at Four to 14 Weeks’ Gestation. Pediatrics, 67(6), 785–789.