Boy-Girl Ratio

18b52763b9The ratio of boys to girls in the United States is 51% to 49% (based the National Longitudinal Study of Youth). Many hypotheses explain why slightly more boys are born each year than girls. Yet no one knows for sure why this is so. A couple of theories aim to explain this:

  • Male infants are more fragile. In fact, they are less likely to survive their first year. So Nature makes up for this with a slightly higher conception rate of males to even out the balance.
  • As Dr. Landrum Shettles contends, Y-bearing (male-producing) sperm may have a speed advantage over X-bearing (female-producing) sperm. Thus male sperm more often win the race up into the fallopian tubes to fertilize the egg. This speed factors thus results in slightly more male conceptions.
  • Because boys and young men engage in more risk-taking behavior across cultures, more boys die by reproductive age and this 51 to 49% ratio is nature’s way of evening the numbers out by reproductive age. That is, more males die, so more males need to be born.

However, the fertility industry has found no data to support these theories in recent years, and reproductive endocrinologists as a whole consider these theories and some based on Shettles theory, unfounded.

What has been validated is that the practice of gender selection via abortions (following ultrasounds, amniocentesis or CVS to determine the fetus’s gender), and infanticide has decreased the percentage of female babies born worldwide. According to the CIA Fact Book, for every 100 babies born in China and India, about 120 – 130 baby boys are born.

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