[Determination of fetal sexes by ultrasonic tomography (author's transl)]

A newly developed manipulation of ultrasonic tomography has been successfully applied for determining the fetal sexes, based on the findings obtained by preliminary studies on the neonatal pelvic and external genitalia. The results are as follows: 1) In neonates, distinct sex differences in length and shape of the anoperineogenital (APG) area were observed by two-dimensional ultrasonic tomography. Transverse tomography of superficial portion of APG gave different images of M for males and of F for females. Frontal tomography produced images of the scrotum and the major labia. 2) In fetuses, distinction in the M and F images of APG between the both sexes was constantly recognized on the 20th week or later. The images representing the triangle formed by the bilateral tuber-ossis ischii and the ventral end of the external genitalia was found quite useful in determining the sexes between the 15th and 20th week of gestation. 3) Determination of fetal sexes in 604 pregnancies (including 4 pairs of twins) between 23th and 39th week of gestation turned out correct in 99.8% of the cases as compared with the sexes after their deliveries. 4) Although feasibility of this method exceeded 50% of the cases of 18th week of gestation, the optimal term for the determination of fetal sexes was estimated between 23 and 32 weeks of gestation.