Sex Preselection Not Yet Practical

 A report on the state of knowledge, current research, and potential effects of sex preselection in humans is presented.  The chromosomal mechanism by which the male gamete determines the sex of the offspring is reviewed.  Theoretically, the sex ratio should be 1:1, though there is a slight preponderance of males to females in the world birthrate.  More than 30 variables have been associated with the variations in the sex ratio.  Variations in the sex ratio imply that conditions in the female/male reproductive tracts favor fertilization by sperm with a particualr sex, and that conditions in the uterus may favor implantation or fetal survival of a particualr sex.  Current research on sex preselection has focused on the timing of coitus (or artificial insemination) in relation to ovulation; precoital pH douching to alter the vaginal environment; the separation of X- and Y-bearing chromosomes by  sedimentation, centrifugation, natural sperm motility, and electrophoresis; immunological methods; and fetal sex identification by amniocentesis with subsequent induced abortion.  Though considerable headway has been made by in utero sex determination, the techniques for sex determination have been either unsuccessful, difficult to standardize, or impractical for sex preselection.  The argument that sex determination would reduce population because of the desire for more sons, and consequently, fewer daughters, is noted.  The argument is supported in part by attitude surveys, but other surveys indicate that more sons may encourage larger families because of increased family wealth.  Generally, the evidence seems to indicate a strong preference for sons in some developing countries, no apparent preference in other developing countries, and a desire for at least 1 child of each sex in developed countries.  The demographic effects of sex control, or an unbalanced sex ratio, cannot be assessed.  Extreme social consequesnces as a result of sex preselection have been predicted by both proponents and opponents of sex determination should an effective, practicable method become available.

Johns Hopkins Bloomberg School of Public Health,Center for Communication Programs,Population Information Program