Unreliability of prenatal determination of fetal sex with the use of Y-body fluorescence in midcervical smears.

A prospective study of midcervical smears from 71 pregnant women was carried out to investigate the validity of Y-body fluorescence as a method for determining intrauterine fetal sex. Endocervical smears were taken below the mucous plug, appropriately stained with Atabrine, and examined using male and female buccal smears as controls. Analysis of the data showed that correct sex of the baby could be predicted only 55 per cent of the time. There was little difference in prediction rate whether the smears were taken in the second or third trimester. The first-trimester smear was the least reliable.