Q&A: When can I find out my baby's sex?

First off, don't believe any of the old wives' tales (or old doctors' tales) about fetal sex. There are no heart rate findings, skin changes, uterine positions, or dangling wedding rings that will identify the sex of your baby! The only way to tell for sure if you're having a boy or girl is by analyzing chromosomes or seeing the fetal genitals.

While some families prefer to find out the sex the old-fashioned way (at birth), others really want to know during pregnancy—whether to make the baby more real to them, or to pick colors for the nursery, I'm not sure.

Invasive genetic testing, by chorionic villus sampling (CVS) or amniocentesis, can determine the sex of the baby by looking at whether the sex chromosomes are XX or XY. Because these procedures carry a small risk of causing a miscarriage or other pregnancy complications, most families won't do genetic testing just for the purpose of determining fetal gender. But if you need chromosome testing for some other reason, the results will include the baby's sex.

Most families find out if they are having a boy or a girl at the time of second trimester ultrasound. Assuming the fetus cooperates, ultrasound can usually identify the sex of the baby by around 18 weeks—a little earlier if you are thin and later if you are heavy. If the baby is hiding his stuff, though, even a good ultrasound technician may not be able to see. And unfortunately, since ultrasound is a medical procedure with some expense involved, your insurance most likely will not pay for another one just to see the sex of the baby—no matter how important it may seem.

If you have a preference for one sex over the other, you may want to think about whether you want to find out during pregnancy or wait until birth. Some moms tell me they want to adjust and feel prepared so if they don't get what they want they will not be disappointed right at the moment of birth, while other moms enjoy the fantasies about girls and boys that they can have during the pregnancy, and feel they will love whatever they get when their new baby is placed into their arms.