Struggle To Get Pregnant Associated With Male BirthsI have previously posted that an acidic cervical environment may encourage conception of a girl. The theory is that female sperm can survive the harsh environment better than male sperm. However, it is interesting that couples who take a long time to get pregnant may be more likely to have boys. I've known a number of women who had boys after a long struggle to get pregnant. Here's an article that may explain why males may be better swimmers:
From the article:
An investigation of 5,283 Dutch women revealed that 57.6 percent of those who took longer than 12 months to become pregnant had boys, compared with 51.1 percent boys among those who became pregnant in less than a year.
"The best-supported hypothesis," said Dr. Luc J. M. Smits, the lead author, "is that the Y chromosome is lighter than the X chromosome, while Y- and X-bearing sperms have the same locomotive power. In liquid fluids, this difference would not cause differential speed, but in viscous fluids it would." Dr. Smits is a lecturer in epidemiology at the University of Maastricht in the Netherlands.