If you’ve decided to find out baby’s sex during your pregnancy, the news probably can’t come soon enough. After all, it’s a huge moment in your prenatal experience, when you can envision life as the parent of a little boy or girl. While it used to be that learning baby’s sex was reserved for the anatomy scan around 18 to 22 weeks of pregnancy, there are now some options that allow you to get that exciting news even sooner. So exactly when can you find out the sex of baby—and how? We’re answering all your questions. Read on for the full lowdown.
First and foremost, it’s important to distinguish between sex and gender. Baby’s sex is determined by their reproductive organs, chromosomes, hormones, etc. Gender, on the other hand, is not predetermined. “Everyone’s gender is unique to them and can be independent of their chromosomal complement,” explains Mark P. Leondires, MD, medical director at Reproductive Medicine Associates of Connecticut. He elaborates: “For example, someone who is born with the chromosome complement 46XY may identify as male, non-binary or female.”
Ready to get a quick biology lesson? It’s all about the chromosomes, baby! Leondires explains: “Chromosome complement is what determines the sex of a baby. Most people have 46 chromosomes. People who are born with ovaries have two X chromosomes (46XX), and people who are born with testes have one X chromosome and one Y chromosome (46XY).” An egg has one X chromosome, so it’s the complementary sperm that’ll either contribute an X or Y chromosome. So if you’re wondering which parent determines the sex of baby, the answer is dad.
If you’re chomping at the bit (and stressing about baby names!), you may want to find out the sex of your little one—you know, before they make their grand entrance into the world. Nowadays, there are many tests that determine baby’s sex. Here are the many ways you can get this intel—and how long you’ll need to wait to get your answer.
Non-invasive prenatal testing (NIPT), also called cell-free DNA testing, is a blood test that’s designed to look for chromosomal abnormalities and conditions in baby, including Down syndrome, trisomy 13 and trisomy 18, says Maura Quinlan, MD, MPH, an assistant professor in the Department of Obstetrics and Gynecology at the Northwestern University Feinberg School of Medicine in Chicago. The test analyzes a sample of your blood, looking at tiny fragments of fetal DNA that are released from the placenta into your bloodstream. While the primary purpose of NIPT is to screen for chromosomal abnormalities, Quinlan says, since the test looks at fetal DNA, it also gives parents the opportunity to find out baby’s sex. If it detects a Y chromosome, you’re carrying a boy; if not, you’re expecting a girl.
What’s the accuracy in sex determination of baby? NIPT is 95 to 97 percent accurate, but it isn’t entirely fool-proof, so “there is always a risk of getting it wrong,” says Jonathan Schaffir, MD, an ob-gyn at the Ohio State University Wexner Medical Center in Columbus, Ohio. Since NIPT is non-invasive, there’s no risk to you or baby. Cost is generally the biggest drawback of this test, since some insurances don’t cover it, Quinlan says.
When can you tell the sex of baby? The test is most reliable starting at 10 weeks of pregnancy, Schaffir says, and results usually take about 10 days.
2. Chorionic Villus Sampling
Chorionic villus sampling (CVS) is a test used to diagnose certain chromosomal abnormalities (like Down syndrome) and genetic problems (like cystic fibrosis) in baby. It can be done one of two ways: By inserting a thin plastic tube through your cervix (known as a transcervical CVS) or a needle through your belly (a transabdominal CVS) to reach the placenta and gather a small sample of placental tissue to test. Your doctor will use ultrasound images to help guide the tube or needle to the best spot for sampling. Like NIPT, CVS looks for genetic abnormalities, but it can also reveal baby’s sex through its testing of cells from the placenta.
What’s the accuracy in sex determination of baby? CVS is close to 99 percent accurate at predicting baby’s sex. That said, it is invasive and comes with a small risk of miscarriage (approximately one in 300-500 women, with transcervical CVS having a higher risk), so this really isn’t recommended for sex determination alone, says Christine Greves, MD, an ob-gyn at the Winnie Palmer Hospital for Women & Babies in Orlando, Florida. It’s also not a test that’s used very often anymore, given that noninvasive prenatal testing can accurately predict genetic issues, she adds. However, if you’re already having CVS to detect genetic problems in baby, you can find out whether you’re having a boy or girl in the process.
When you can tell the sex of baby? CVS can be done starting at 10 weeks of pregnancy. After the test is performed, the sample is placed in a dish and sent off to a lab, and it can take about two weeks to get the test results.
Amniocentesis (you may hear it referred to as an “amnio”) is a diagnostic test that’s usually done between 15 and 20 weeks of pregnancy. To do the test, a technician will insert a very thin needle into your amniotic sac to draw a little amniotic fluid. That fluid, which contains cells that baby has shed, is then analyzed to look for genetic abnormalities.
What’s the accuracy in sex determination of baby? “Amnio is considered the ‘gold standard’ for determining information from fetal DNA, including gender, because it’s nearly 100 percent accurate,” Schaffir says. “However, it is invasive, so there’s a small amount of pain involved and there is a risk of causing infection or bleeding within the pregnancy sac that could at worst cause miscarriage.” Because of this, amnio is not recommended if you’re just trying to find out baby’s sex, given that the test does pose some risk to baby, Quinlan says.
When can you tell the sex of baby? Amniocentesis is typically performed as early as 15 weeks of pregnancy, and results usually take between seven to 10 days, Schaffir says, but could take up to approximately 2 weeks.
Baby’s external genitals are fully formed by about 14 weeks of gestation, so technically an ultrasound done anytime after that could help determine baby’s sex, Schaffir says. But since all of their anatomical development isn’t complete until around 18 to 20 weeks, that’s usually when the anatomy scan is performed. Unless your little one’s position makes it hard to see, your ultrasound technician can provide a visual confirmation of baby’s sex.
What’s the accuracy in sex determination of baby? “Accuracy is around 97 to 99 percent, depending on the skill of the sonographer and the position of the fetus,” Schaffir says. “So, again, there is a risk of getting it wrong.”
When you can you tell the sex of baby? The results are instant—you can find out baby’s sex in real time during your ultrasound appointment. Plus, the ultrasound poses no risk to you or baby.
It’s possible to determine the sex of a potential baby before an embryo is transferred during IVF (in vitro fertilization). According to American College of Obstetricians and Gynecologists, preimplantation genetic testing involves examining an embryo for any possible genetic abnormalities or birth defects. At this time, the chromosome pairing (XX or XY) can also be identified to indicate sex. Preimplantation genetic testing can also be used for sex selection during IVF; that means that parents specifically seek out an XX chromosome pairing for a girl or an XY chromosome pairing for a boy, notes CNY Fertility.
What’s the accuracy in sex determination of baby? Since an XX or XY is actively identified, accuracy is almost 100 percent, according to CNY Fertility.
When you can you tell the sex of baby? In this scenario, the embryo’s chromosomes are evaluated in anticipation of it being transferred into a mom’s uterus—so sex determination actually happens before pregnancy.
6. Home Gender Predictor Test Kit
You may have spotted these kits at your local drugstore and wondered what they were all about. First and foremost, while they’re often labeled and marketed as “gender predictors,” they’re actually used to determine baby’s sex. However, they vary, both in how they work and how accurate they are. Some test urine while others test blood. But across the board, they’re not sanctioned by any major medical organization.
What’s the accuracy in sex determination of baby? There are some tests out there that claim to determine sex based on maternal urine, but they’re very unreliable, Schaffir says. Others have you collect a blood sample and mail it in for a DNA test. “Since these are mailed to laboratories of uncertain reputation that may or may not have gone through the certification process needed to prove their reliability, the results may or may not be accurate,” he says. “I’d say it’s better to go through a lab recommended by your prenatal care provider.” Quinlan agrees: “They’re not FDA-approved. I wouldn’t rely on the results.”
When can you tell the sex of baby? How quickly you can get results varies based on what kind of predictor test kit you use, but some, like the “SneakPeek Early Gender DNA Test,” promise to give you results in less than 72 hours after you place your order. Remember, these aren’t FDA-approved and it’s hard to say how reliable they actually are.
In general, doctors say the anatomy scan and non-invasive prenatal testing are the best, most reliable and safest options for determining baby’s sex. If you’re not sure what you want to do, talk to your doctor, who’ll be able to guide you.
Again, sex and gender are different things. Eventually, children will begin to develop their own gender identity; this is a person’s inner sense of how they identify themselves—male, female or neither. “We see that many children become more aware of gender identity as early as 2 to 3 years of age,” says Leondires.
Finding out the sex of baby can be a wonderful moment. Talk to your doctor to decide which test for sex determination is right for you. Of course, you can also choose to wait it out for a big delivery day surprise.
Please note: The Bump and the materials and information it contains are not intended to, and do not constitute, medical or other health advice or diagnosis and should not be used as such. You should always consult with a qualified physician or health professional about your specific circumstances.
Christine Greves, MD, is an ob-gyn at the Winnie Palmer Hospital for Women & Babies in Orlando, Florida.
Mark P. Leondires, MD, is an ob-gyn and reproductive endocrinologist and the founder and medical director of Reproductive Medicine Associates of Connecticut (RMA of CT). He is also the founder of Gay Parents To Be (GPTB), a family building resource for the LGBTQ+ community and a founder at Gays with Kids (GWK). He earned his medical degree from the University of Vermont in Burlington.
Jonathan Schaffir, MD, is an ob-gyn at the Ohio State University Wexner Medical Center in Columbus, Ohio.
Maura Quinlan, MD, MPH, is an assistant professor in the Department of Obstetrics and Gynecology at the Northwestern University Feinberg School of Medicine in Chicago.
Cleveland Clinic, 20 Week Ultrasound (Anatomy Scan), April 2022
National Institutes of Health, Office of Research on Women’s Health, Sex & Gender
Nemours KidsHealth, Week 2
MedlinePlus, Prenatal Cell-Free DNA Screening
Cleveland Clinic, NIPT Test, October 2022
Journal of Community Genetics, The Impact of Insurance on Equitable Access to Non-Invasive Prenatal Screening (NIPT): Private Insurance May Not Pay, January 2021
UT Southwestern Medical Center, What Noninvasive Prenatal Testing Can (and Can’t) Tell You About Your Baby, June 2023
UCSF Health, FAQ: Chorionic Villus Sampling (CVS)
Cleveland Clinic, Chorionic Villus Sampling for Prenatal Diagnosis, June 2021
Cleveland Clinic, Amniocentesis, April 2022
Nemours KidsHealth, Week 14
March of Dimes, Ultrasound During Pregnancy, October 2019
American College of Obstetricians and Gynecologists, Preimplantation Genetic Testing, March 2020
F&S Reports, Preimplantation Sex Selection via In Vitro Fertilization: Time for a Reappraisal, September 2023
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