DETERMINATION OF FETAL SEX BY ULTRASOUND Prenatal fetal sex determination plays an important role in the management of certain genetic disorders. It has been successfully employed in the second trimester of pregnancy. Chromosome analysis of cells obtained from amniocentesis and grown in tissue culture is the generally accepted procedure, although other techniques have been employed. Determination of fetal sex at later periods of gestation has no clinical application, nonetheless, the temptation exists t o define fetal sex in utero especially as newer, more sophisticated techniques and instruments are developed. The imaging provided by ultrasonic scanning, particularly with real-time instruments, has provided new impetus t o those physicians who desire to satisfy either their curiosity or that of their patients and attempt to determine fetal sex. This determination depends on identification of the scrotum and penis or in absence of this finding inference that a female fetus is present. The technique is totally unreliable prior to the last trimester of pregnancy. In addition, such factors as decreased amounts of amniotic fluid, engaged breech presentations, anterior position of the fetal back will make the determination of fetal sex difficult or impossible. In one study (Stocker, J. & Evens, L., Fetal Sex Determination by Ultrasound, Obstet & Gynecol. 50: 462-466, 1977), it was possible to visualize the perineal area in only 54% of 229 attempted studies. When only those instances of definite perineal visualization are evaluated, sex determination was correct in 95.6% (99.5% for identified males; 91.5% for identified females). Clearly, the results, particularly if all attempted studies are included, do not justify the employment of ultrasound t o determine fetal sex. At this time, no clinical usefulness of the procedure is apparent. If, in the future, a clinical need does arise, refinement of technique will be necessary prior t o its use. Richard Bernstine Dept. of Obstetrics-Gynecology St. Elizabeth's Hospital Youngstown, Ohio

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