Finding out the sex of your baby is such an exciting part of pregnancy. While some people choose to be surprised at the time of delivery, many couples want to know the sex of the baby before they give birth.
XX or XY
Your baby’s sex is determined at the moment of conception. Of the 46 chromosomes that make up your baby’s genetic material, two chromosomes–one from the egg and one from the sperm–determine your baby’s gender. A woman’s egg contains only X sex chromosomes. A man’s sperm, however, may contain either an X or Y sex chromosome. If, at the instant of fertilization, a sperm with an X sex chromosome meets the egg (another X chromosome), your baby will be a girl (XX). If a sperm containing a Y sex chromosome meets the egg, your baby will be a boy (XY). It is always the father’s genetic contribution that determines the sex of the baby.
How can I find out the sex of my baby?
Most women find out their baby’s sex during a routine ultrasound in the second trimester—usually between 18-20 weeks. Traditional ultrasound is approximately 93% to 100% accurate at detecting the baby’s sex. But, just remember that sometimes the sex is not clearly identifiable from an ultrasound. This is usually due to the position of the baby.
While ultrasound is accurate, if you want to be absolutely certain of your baby’s sex, you would need a diagnostic test, such as a CVS (done between 10-12 weeks of pregnancy) or amniocentesis (done between 15-20 weeks of pregnancy). It is important to keep in mind that these prenatal tests are invasive and are done primarily to diagnose certain genetic conditions, such as Down syndrome.
Another way you may find out if you are having a boy or a girl is through cell-free fetal DNA testing (also called noninvasive prenatal testing or NIPT). NIPT tests your blood for your baby’s DNA to see if he may have certain genetic conditions, like Down syndrome. While this test is not used specifically to determine the baby’s sex, it can provide that information. It can be done after 10 weeks of pregnancy.
Did you find out if you were having a boy or a girl? Did you reveal it in a special way? Let us know—we’d love to hear your stories!
Have questions? Email us at AskUs@marchofdimes.org.