How Many Weeks Does It Take to Tell if You're Having a Boy or Girl?

Wondering when you can learn about your child’s biological sex? Your child will begin to develop sexual characteristics around the 14th week of pregnancy, but you may want to wait for the ultrasound at 18-21 weeks before you investigate your child’s sex. In this article, we’ll walk you through all of your options when it comes to determining your child’s sex. We’ll also debunk a few common myths about determining your kid’s sex at home. Read on to learn more!

Section 1 of 6:

When does a baby develop sexual characteristics?

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    A child develops sexual characteristics form around the 14th week. Your child’s biological sex is determined by their chromosomes, but it takes time for the fetus to develop sexual characteristics. Some fetuses develop a little faster or slower than one another, but your baby should begin developing clear sexual characteristics at the 14th week.[1]
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Section 2 of 6:

When can an ultrasound tell a baby’s sex?

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    You can learn your baby’s sex at 18-21 weeks. The mid-pregnancy scan (aka the anomaly scan) is the ultrasound you’ll get around 20 weeks. The scan is meant to check the physical development of your child, but your child’s sexual characteristics will be developed enough for the ultrasound tech to tell you whether it’s a boy or a girl. Just mention before the scan that you’d like to know the sex.[2]
    • This is widely considered to be the most accurate non-invasive option out there. It appears to be roughly 98% accurate.[3]
    • A sonographer may be able to make an educated guess at 11-14 weeks. It won’t be a 100% positive result (at 11 weeks, the accuracy is about 75%), but you can ask the ultrasound technician or doctor to give it their best shot.[4]
Section 3 of 6:

When can a blood test determine sex?

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    A prenatal blood test (NIPT) can determine sex after 10 weeks. The non-invasive prenatal test (NIPT) is a genetic test that screens the mother’s blood for certain chromosomal disorders. You can get this test any time after the 10[5] The accuracy of the sex determination based on the NIPT test is around 98%, although it may not give you a result for biological sex.[6]
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Section 4 of 6:

Can at-home tests find a baby’s sex?

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    The OTC urine tests don’t appear to work. If you swing by a pharmacy or corner store, you might see sex determination tests where you pee into a cup and then place a strip into the cup and wait for it to change color. There isn’t a ton of research out there on these, but they don’t seem to be accurate. There are no sex hormones in the mother’s urine, so the premise behind the test isn’t particularly sound.[7]
    • There are blood test at-home kits for this as well. They make sense in theory, but the results aren’t reputable. There’s just no way to know what the lab you’re sending the blood test to is doing with the sample, so you can’t trust the results.[8]
Section 5 of 6:

Are there any other tests that will determine sex?

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    The CVS and amniocentesis tests can signal the sex after 10-12 weeks. These tests are used to screen for fetal infections, developmental disorders, and DNA screenings.[9] Both tests involve a doctor extracting a sample of the placenta for analysis.[10] If you have either test performed, ask the doctor to check for sex when they analyze the results.[11]
    • These tests are invasive, and they’re typically not encouraged if there isn’t a specific risk the doctor wants to assess.
    • Talk to your doctor before having either of these procedures. There may be side effects, and there’s a very minor chance that they’ll induce a miscarriage, so don’t get one of these tests if you don’t need them.[12]
    • When it comes to determining biological sex, the accuracy of these tests is around 90%, so it’s not the best option for sex determination anyway.[13]
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    The cfDNA screening can determine sex after 10 weeks. The cell-free DNA prenatal screening is an optional genetic test used to screen for down syndrome and other common genetic disorders. Depending on how developed the fetus is, you may be able to determine your child’s biological sex using this test.[14]
    • Many patients opt for this test specifically because it’s an accurate way to determine a child’s sex. However, it can signal that you’re at high risk for genetic disorders, even if your child doesn’t have that disorder. Talk to a doctor to weigh the pros and cons of getting a cfDNA test.[15]
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Section 6 of 6:

Common Myths

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    It's impossible to determine sex without a medical professional. It’s certainly fun to come up with tests and tricks you can do at home to predict your baby’s sex, but there's no surefire way to do this. Old wives’ tales and legends are enjoyable ways to speculate about your baby's sex, but there isn’t any scientific evidence that any of these "signs" are accurate.[16] These “signs” have been debunked by science and can't determine biological sex:
    • The size and location of a baby bump[17]
    • The size and symmetry of your breasts during pregnancy[18]
    • The severity of morning sickness (although extreme morning sickness could possibly mean you’re having twins or triplets)[19]

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References

  1. ↑ https://www.mayoclinic.org/healthy-lifestyle/pregnancy-week-by-week/in-depth/fetal-development/art-20046151
  2. ↑ https://www.nhs.uk/pregnancy/your-pregnancy-care/20-week-scan/
  3. ↑ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3530251/
  4. ↑ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5024945/
  5. ↑ https://www.ohsu.edu/sites/default/files/2019-06/Non-Invasive-Prenatal-Testing-FACTSHEET_1.pdf
  6. ↑ https://www.fhi.no/en/publ/2016/ikke-invasiv-prenatal-testing-nipt-for-kjonnsbestemmelse-av-foster.-metodev/
  7. ↑ https://www.parents.com/pregnancy/my-baby/gender-prediction/gender-prediction-kits-are-they-accurate/
  8. ↑ https://www.parents.com/pregnancy/my-baby/gender-prediction/gender-prediction-kits-are-they-accurate/
  9. ↑ https://www.mayoclinic.org/tests-procedures/amniocentesis/about/pac-20392914
  1. ↑ https://www.mayoclinic.org/tests-procedures/chorionic-villus-sampling/about/pac-20393533
  2. ↑ https://pubmed.ncbi.nlm.nih.gov/12124698/
  3. ↑ https://www.hopkinsmedicine.org/health/treatment-tests-and-therapies/chorionic-villus-sampling-cvs
  4. ↑ https://pubmed.ncbi.nlm.nih.gov/12124698/
  5. ↑ https://www.mayoclinic.org/tests-procedures/first-trimester-screening/about/pac-20394169
  6. ↑ https://www.jax.org/news-and-insights/jax-blog/2020/january/pre-natal-cell-free-dna-screening#
  7. ↑ https://www.nct.org.uk/pregnancy/worries-and-discomforts/common-discomforts/gender-positions-and-cravings-pregnancy-truth-or-myth
  8. ↑ https://www.uofmhealth.org/health-library/te6295
  9. ↑ https://pubmed.ncbi.nlm.nih.gov/25833467/
  10. ↑ https://www.nct.org.uk/pregnancy/worries-and-discomforts/common-discomforts/gender-positions-and-cravings-pregnancy-truth-or-myth
  11. ↑ https://www.ons.gov.uk/economy/environmentalaccounts/articles/whatisthedifferencebetweensexandgender/2019-02-21

About This Article

Denise Stern
Co-authored by:
Denise Stern
Parenting Specialist
This article was co-authored by Denise Stern and by wikiHow staff writer, Eric McClure. Denise Stern is a Parenting Specialist and the CEO of Let Mommy Sleep, the country’s leading Baby Nurse and Postpartum Care service. Denise specializes in providing nurturing care to newborns and evidence-based education to their parents. She holds a BA in Public Relations from North Carolina State University. Denise was the US Chamber of Commerce Leading Woman-Owned Business in 2013, a Washington FAMILY Magazine Mother of the Year in 2016, and on the elite White House Summit for Working Families hosted by the President and First Lady Obama in 2014. Let Mommy Sleep is the only company of its kind that holds a local government contract to teach newborn and postpartum care. This article has been viewed 8,074 times.
1 votes - 100%
Co-authors: 6
Updated: April 4, 2022
Views: 8,074
Categories: Pregnancy

Medical Disclaimer

The content of this article is not intended to be a substitute for professional medical advice, examination, diagnosis, or treatment. You should always contact your doctor or other qualified healthcare professional before starting, changing, or stopping any kind of health treatment.

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