Early second-trimester determination of fetal gender by ultrasound.

Ultrasound identification assists in determining chorionicity in twins, in the interpretation of sex chromosome mosaicism and aneuploidy and in sex-linked conditions presenting after 14 weeks. This study addresses the frequency and accuracy of gender identification in a series of consecutive patients presenting for amniocentesis for genetic indications. Amniocentesis was performed at 14-20 weeks in 843 fetuses over a 5-year period. Ultrasound prediction of fetal gender was documented in 93.3% (770/843). The overall accuracy of diagnosis of fetal gender was 99.3% (765/770). Errors in diagnosis of gender were more likely to occur in the assessment of the female fetus. Such errors in diagnosis may be minimized by combining both tangential/transverse and sagittal views of the fetal perineum.