Most parents find out their baby’s sex around month 5 of pregnancy, during the anatomy scan ultrasound performed between 18 and 22 weeks. But depending on the method, you can learn the sex much earlier, sometimes as soon as 6 or 7 weeks into pregnancy with a blood test.
The Earliest Option: Blood Tests Starting at 6 Weeks
The earliest way to learn your baby’s sex is through a blood test that detects fragments of fetal DNA circulating in your bloodstream. At-home consumer tests like SneakPeek use this approach and claim to work as early as 6 weeks of pregnancy, which is barely into month 2. In published studies, these consumer tests have shown accuracy rates above 99% when used at 7 weeks or later. A 2022 study of 103 women reported 100% accuracy at 6 weeks gestational age.
A clinical version of this blood test, called NIPT (noninvasive prenatal testing), is available starting at 10 weeks. NIPT is primarily used to screen for chromosomal conditions like Down syndrome, but it also identifies fetal sex as part of the results. It takes about 10 weeks of pregnancy for enough fetal DNA to build up in your blood for the clinical test to work reliably. Your provider may offer NIPT if you’re over 35 or have other risk factors, though many practices now offer it to all pregnant patients.
Diagnostic Tests: 10 to 16 Weeks
Two diagnostic procedures can also reveal fetal sex, though they’re not done for that purpose alone. Chorionic villus sampling (CVS) happens between weeks 10 and 13, and amniocentesis happens around week 16. Both are about 99% accurate because they directly analyze fetal chromosomes. These tests are typically recommended when there’s a specific concern about genetic conditions, not simply to learn the sex. But if you’re having one done for medical reasons, sex determination comes along with the results.
The Anatomy Scan: 18 to 22 Weeks
For most pregnancies, the anatomy scan ultrasound is when parents first see their baby’s sex on screen. This scan happens between 18 and 22 weeks, placing it right around month 5. The primary purpose is to check fetal organ development and screen for structural issues with the brain, heart, kidneys, and other organs, but it also gives a clear view of the genitalia in most cases.
Clinical guidelines recommend that fetal sex determination be included as part of this standard scan. If you want to know, the sonographer will typically tell you during the appointment. If you’d rather be surprised, let them know beforehand. Ultrasound reports are supposed to include a visible alert about sex information so you don’t accidentally read it.
Why the Ultrasound Sometimes Can’t Tell
Even at 18 to 22 weeks, there are situations where the sonographer can’t get a clear view. The most common obstacle is fetal position. If the baby’s legs are crossed or the body is turned away, the genitalia simply aren’t visible. In one study, 76% of sonographers who couldn’t determine sex pointed to fetal position as the main reason. Low amniotic fluid levels and higher maternal body weight can also reduce image clarity. When the sex can’t be determined, a follow-up scan or referral is typically recommended.
Earlier ultrasounds are less reliable. Between 11 and 14 weeks, sonographers can attempt to identify sex based on the angle of a small structure called the genital tubercle. But a study in the American Journal of Obstetrics and Gynecology found this method was only about 84% accurate, and sex couldn’t be assigned at all in about 13% of cases. That’s a meaningful error rate compared to the near-certainty of blood tests or the 18-to-22-week scan.
Which Method Is Right for You
Your timeline depends on what’s available and what matters most to you. Here’s a quick comparison:
- At-home blood test (6 to 10 weeks): Fastest option, over 99% accuracy in studies, costs out of pocket, not a medical screening
- NIPT blood test (10+ weeks): Clinical test with high accuracy, also screens for chromosomal conditions, may be covered by insurance
- CVS or amniocentesis (10 to 16 weeks): 99% accurate, only performed when there’s a medical indication
- Anatomy scan ultrasound (18 to 22 weeks): Standard for all pregnancies, visual confirmation, occasionally limited by baby’s position
If patience isn’t your strength and you want the answer as early as possible, a consumer blood test at 7 or 8 weeks is the fastest route with strong accuracy data behind it. If you’re content to wait, the anatomy scan at month 5 gives you a reliable answer during an appointment you’ll already have scheduled. Either way, you won’t have to wait until delivery day unless you choose to.