Gender Selection Methods - Scientific Evidence?
Gender Selection Methods by Intercourse Timing: Review of Published Scientific Articles
Can you choose the sex of your baby?
Many couples are interested in gender selection methods, particularly the Shettles Method. But is there any scientific evidence that you can actually choose the sex of your baby using this method? To answer this question, we have conducted a brief review of the scientific literature in this field.
In 1970, Landrum B. Shettles published an article called "Factors influencing sex ratios" in the International Journal of Gynaecology and Obstetrics. The premise, which he later expanded for a book which popularized his theory, is that your intercourse timing and your reproductive environment can influence the gender of your offspring (See Shettles theory summary).
Since that time, many researchers have sought to test Shettles theory. A review of the published scientific literature in the field of gender selection and prediction, however, yields conflicting claims. The majority of studies find little or no correlation with timing of intercourse and the sex of offspring. Some studies actually claim that the opposite of Shettles’ theory may be true.
John T. France and colleagues, for example, in an article published in 1992 in The International Journal of Fertility say "...our findings tend to disprove the Shettles theory..." Likewise, RH Gray, in a 1991 article in American Journal of Obstetrics and Gynecology says that the Shettles method is contradicted by scientific data. Finally, in a 1995 study published in the New England Journal of Medicine, researchers Allen Wilcox, Clarice Weinberg and Donna Baird say that "the timing of sexual intercourse in relation to ovulation has no bearing on the sex of the baby".
There has been some speculation, however, that another factor may play a role in gender determination. In a 1995 article in Human Reproduction, Weinberg, Baird, and Wilcox suggest that the length of the follicular phase (the time between menstruation and ovulation) is related to the sex of the baby. They suggest that cycles with shorter follicular phase lengths are slightly more likely to result in male babies, while cycles with longer follicular phases are more likely to result in female babies. This theory, however, has also been disputed. Gray and Simpson, in a 1998 article in Human Reproduction say that there is no association between follicular phase length and sex ratio.
Most parents-to-be who are trying to conceive would be delighted to be expecting a child of any gender. Still, interest in gender selection and prediction abounds for a variety of reasons. And it is not hard to find parents who claim that one technique or another was successful for them. Nonetheless, the majority of scientific studies suggest that there is no clear evidence that you can use intercourse timing to increase the likelihood of conceiving a particular gender.
Without any clear evidence that you can dramatically increase the odds of conceiving a boy or a girl, limiting intercourse within the fertile period is not recommended for couples who wish to conceive quickly or those who are experiencing difficulty conceiving.
Indeed, there is evidence that limiting intercourse within the fertile time will reduce your chances of conceiving any child (See Intercourse Timing Study). Our recommendation for couples who are trying to conceive, especially those who are anxious to conceive quickly, is thus to avoid any techniques that limit intercourse within the most fertile time. Couples who are concerned about sex-specific genetic diseases or couples who could not be satisfied with a child of either gender are advised to seek the counsel of their healthcare provider before trying to conceive.
France, J. T., F. M. Graham, et al. (1992). "Characteristics of natural conceptual cycles occurring in a prospective study of sex preselection: fertility awareness symptoms, hormone levels, sperm survival, and pregnancy outcome." Int J Fertil 37(4): 244-55.
France, J. T., F. M. Graham, et al. (1984). "A prospective study of the preselection of the sex of offspring by timing intercourse relative to ovulation."Fertil Steril 41(6): 894-900.
Gray, R. H. (1991). "Natural family planning and sex selection: fact or fiction?" Am J Obstet Gynecol 165(6 Pt 2): 1982-4.
Gray, R. H., J. L. Simpson, et al. (1998). "Sex ratio associated with timing of insemination and length of the follicular phase in planned and unplanned pregnancies during use of natural family planning." Hum Reprod 13(5): 1397-400.
Martin, J. F. (1997). "Length of the follicular phase, time of insemination, coital rate and the sex of offspring." Hum Reprod 12(3): 611-6.
Weinberg, C. R., D. D. Baird, et al. (1995). "The sex of the baby may be related to the length of the follicular phase in the conception cycle." Hum Reprod 10(2): 304-7.
Wilcox, A. J., C. R. Weinberg, et al. (1995). "Timing of sexual intercourse in relation to ovulation. Effects on the probability of conception, survival of the pregnancy, and sex of the baby." N Engl J Med 333(23): 1517-21.