[Ultrasound determination of the foetal sex (author's transl)].

Determination of the foetal sex in utero by ultrasonography is possible after the sixth month of pregnancy. In 100 women examined during the last trimester (15 with breech presentation and 85 with cephalic presentation) the sex of 28 boys and 34 girls could be diagnosed. This represents 72,9% positive determinations, if breech presentations are excluded. The best results are in fact obtained in cephalic presentations. One cause of error is spina bifida, which might give images resembling the scrotum (one case in our study). This examination is of interest mainly in cases of sex chromosome abnormalities.