It's one of the first things that everyone asks a pregnant woman: Is it a boy or a girl?
Throughout history, many parents didn't want to wait until the actual birth to find out. They'd wave crystals over the mother or consult the stars. They'd hang a ring over the mother's tummy or measure the baby's heart rate -- and have at least a 50/50 chance of guessing correctly.
Now, of course, there are much more accurate ways to determine gender before a baby is born. If you're at least 12 weeks pregnant, your doctor can probably tell you the sex of your baby with a high degree of confidence. That is, if you really want to know.
Parents who want to pick out a name or stock up on baby clothes before the big day often look forward to their ultrasound appointment. Not only do they get to see an image of their baby, but they also have a good chance of learning its gender. (Doctors routinely use ultrasound imaging early in pregnancy to measure a baby's size and check for birth defects or other problems, not to check gender.)
By the 12th week of pregnancy, most babies have distinctly male or female genitals, and ultrasound can provide a good view of the sex organs if the baby happens to be in the right position. A study published in Ultrasound Obstetrics and Gynecology found that ultrasound was about 70 percent accurate at determining gender in the 11th week. By the 12th week, accuracy jumps to nearly 99 percent. By the 13th week, a good ultrasound picture is extremely accurate.
Still, don't count on it to be foolproof. Babies don't always cooperate when they're having their picture taken. Ask the doctor or ultrasound technician if he or she really got a clear, unobstructed view of the baby's genitals. If the expert is confident, you can be too. If not, you just might have to wait for another ultrasound or find out on the big day.
Any test that involves taking a genetic sample from the baby, such as amniocentesis or chorionic villus sampling (CVS), can also determine gender with near-perfect accuracy. However, these tests occasionally cause miscarriage (a 2006 study found the risk to be roughly 1 in 370 pregnancies). For that reason, a doctor would not use them solely to tell if a baby is a boy or a girl. But if you're having one of these tests for another reason, and still want to know the gender of your baby, it's a good time to ask.
And then there's the other option: waiting until the baby is actually born. When you finally hold that little bundle in your arms, you'll learn all you need to know. Boy or girl, it will be yours.
Center for Genetics and Society, It's a Boy! We Made Sure of It. http://www.genetics-and-society.org/resources/items/20041103_ebexpress_platoni.html
University of Michigan Health System. Ultrasound scanning in pregnancy. 2004. http://www.med.umich.edu/1libr/wha/wha_utz_crs.htm
Fairbanks Clinic, Ob-Gyn Ultrasound at the Fairbanks Clinic, September 2003, http://www.obgynsono.com/overview.html
March of Dimes, Quick Reference: Amniocentesis, April 2007 http://www.marchofdimes.com/professionals/14332_1165.asp
March of Dimes, Quick Reference: Chorionic Villus Sampling, April 2007 http://www.marchofdimes.com/professionals/14332_1165.asp
ACOG News Release: Risk of Miscarriage from Prenatal CVS Test Much Less Than Previously Believed. August 31, 2006.
Efrat Z et al. First-trimester determination of gender by ultrasound. Ultrasound Obstetrics and Gynecology 13(5): 305-307.