The Longer It Takes to Get Pregnant, the Greater the Chances of Having a Boy
It remains a mystery why there are more boys born than girls. The proportion of sperm carrying X chromosomes (which produce girls) is equal to that of sperm carrying Y chromosomes (which produce boys). And once conceived, male embryos and fetuses are at higher risk of miscarrying than females. Nevertheless, there are 105 boys born to every 100 girls in most countries throughout the world.
In a new study in the December 17, 2005 issue of the British Medical Journal , researchers found that women who try to get pregnant for more than 12 months before conceiving are significantly more likely to have boys than those who successfully conceive after trying for 12 months or less.
About the Study
This study included 5,283 Dutch women who gave birth to single babies between July 2001 and July 2003. Researchers gathered information on the time it took the women to get pregnant, and analyzed whether time to pregnancy affected the sex of the baby.
Among the 498 women who tried to get pregnant for longer than 12 months, 57.6% had boys. By contrast, only 51.1% of the women who tried to get pregnant for 12 months or less had boys. The researchers calculated that each additional year of trying to get pregnant is associated with a nearly 4% higher probability of delivering a boy.
How Does This Affect You?
These findings suggest that the longer it takes to get pregnant, the more likely the baby will be a boy. The study cannot determine why time to pregnancy affects the sex of the baby, but the authors propose a theory. For natural conception, sperm must penetrate cervical mucus. The thickness of cervical mucus varies, and women with thicker cervical mucus often have a harder time getting pregnant. Experiments have shown that Y-bearing sperm (those that produce males) swim faster than X-bearing sperm (those that produce females). So, women who take longer to get pregnant may tend to have thicker cervical mucus, thus increasing their chances of having a boy.
While its probably not a good idea to choose paint colors for the nursery based on how long it took you to get pregnant, at least you now have some information to help you predict what you’ll be bringing home: a baby girl or baby boy (assuming, of course, the ultrasound doesn’t tip you off).
American Society for Reproductive Medicine
National Women’s Health Information Center
Smits LJM, de Bie RA, Essed GG, van den Brandt PA. Time to pregnancy and sex of offspring: cohort study. BMJ . 2005;331:1437-1438.
Last reviewed Dec 21, 2005 by ]]>Richard Glickman-Simon, MD]]>
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