How soon can I find out my baby's sex?

Some parents want the sex of the baby to be a surprise, while others plan large gender reveal parties. Here's how many weeks until you can know.

Baby wearing diaper playing with mom milanzeremski/shutterstock

This is one of the most common questions doctors get from parents-to-be. If you're dying to know whether to stock up on pink or blue onesies, you'll likely have to wait until you're about 18 to 20 weeks along. Doctors can usually determine the baby's sex during a routine ultrasound visit at this time, but not always.

The position of the baby during the ultrasound is key, and if your baby's curled up or facing the wrong way, you may have to wait until your next appointment. For obvious reasons, it's usually easier to see if your baby is a boy.

Moms-to-be who undergo amniocentesis—a prenatal test that's used to check for certain genetic problems, usually around 16 weeks—can also find out whether they're having a boy or a girl at that time. The test, usually given to moms 35 or older, involves inserting a needle into the uterus to remove a small amount of amniotic fluid. It's not performed simply to determine your baby's sex.