Development in the first half of gestation of genetically abnormal human fetuses.

Linear measurements, total weight and organ weights were determined for 24 second trimester human fetuses with a cytogenetic or metabolic defect. The three fetuses with trisomy 13 or 18 tended to be smallest in all parameters. This data should be of value to other laboratories interested in human fetal growth. It demonstrates that the intrauterine growth retardation reported at term in cytogenetically abnormal newborns is already manifested at the eighteenth to twentieth week of gestation.