When Can You Find Out the Baby's Gender? Blood Test vs Scan (Weeks Explained)
Two routes, two timelines. A blood test from 10 weeks, or the mid-pregnancy scan at 18 to 22 weeks. Here is what to expect from each, with sources, and when to book the party.
In this guide · 6
Short answer: a cell-free DNA blood test (often called NIPT) can be done from 10 weeks of pregnancy and reports the baby's sex chromosomes along with its main screening results. If you are not having that test, the anatomy ultrasound at 18 to 22 weeks is when most parents find out. Either way, your midwife or doctor confirms the result and tells you how confident they are. A party should wait until you have that word.
| Route | Earliest week | How it works | Who offers it |
|---|---|---|---|
| Cell-free DNA blood test (NIPT) | 10 weeks | A sample of the mother's blood; the lab reads DNA from the placenta | Most clinics on request; sometimes private, sometimes not covered |
| Anatomy ultrasound (the 20-week scan) | 18 to 22 weeks (NHS: 18 to 21) | The sonographer looks between the legs during the detailed scan | Routine almost everywhere; telling the sex is optional, and some hospitals don't |
| Diagnostic tests (CVS, amniocentesis) | CVS from about 10 to 13 weeks; amnio from about 15 | Chromosome analysis; sex is a by-product | Only when there is a medical reason |
| IVF with embryo testing (PGT) | Before transfer | The embryo's chromosomes are already known | Only in IVF clinics that offer PGT |
The blood test (cell-free DNA / NIPT): from 10 weeks
From about the 10th week, a small amount of the placenta's DNA is in the mother's bloodstream. The American College of Obstetricians and Gynecologists (ACOG) says this cell-free DNA test "can be done starting at 10 weeks of pregnancy" and that it screens for Down syndrome, trisomy 13, trisomy 18 "and problems with the number of sex chromosomes". Because it reads the sex chromosomes, the report can say whether they are XX or XY, and most labs tell you if you ask.
- It is a screening test, not a diagnosis. Clinics describe the sex result as highly accurate once there is enough placental DNA in the sample, and accuracy rises with the week of pregnancy. Ask your clinic what figure they quote for their lab.
- Too early is the usual reason for a wrong or missing result. Before 10 weeks there is often not enough DNA, and the lab asks for a second sample.
- Twins change things. With twins, the test can tell whether there is at least one boy, but not always which baby.
- Results take a few days to two weeks, depending on the lab and the country.
The anatomy scan: 18 to 22 weeks
ACOG describes a standard ultrasound "usually performed at 18–22 weeks of pregnancy" that checks the brain, spine, heart, limbs and the rest of the baby's body. In the UK the NHS offers this scan "between 18 and 21 weeks" and says that during it "you may be asked if you'd like to know the sex of your baby". Finding out the sex is not the purpose of the scan, so a few things can get in the way:
- Position. If the baby's legs are crossed or the cord is in the way, the sonographer may not be able to see. Some clinics offer a second look later; others don't.
- Hospital policy. Some hospitals and some countries do not tell parents the sex at all. Ask before the appointment so nobody is disappointed on the day.
- It is a visual judgement. Sonographers are usually right at this stage, but the scan is less certain than the DNA test, and the earlier the scan, the less certain it is.
What about earlier scans and home tests?
A dating scan at 11 to 14 weeks is not designed to show the sex, and a guess made then is just that. Online "gender prediction" quizzes, the Chinese calendar, heartbeat myths and ring tests are games: fun at a party, no better than a coin toss. If you want the entertainment, our old wives' tales quiz says so plainly on the page. Home urine kits sold online are not a recognised test and are not used by clinics.
Planning the reveal around the result
Many families get the result in the second trimester, when energy is back and the pregnancy is public. That is why so many gender reveals and baby showers land between weeks 16 and 24, with the shower a little later (when to have a baby shower). Three timing tips:
- Let the clinic seal it. Ask the sonographer or the lab to write the result in a sealed envelope or send it to one trusted person, so the parents can be surprised too. Our game does the same job online: the gender is sealed in the party and only the winner sees it first. See how a reveal works when the parents don't know.
- Pick the date after the result, not before. Scans get rescheduled, and the baby may not cooperate. Book the party for a week or two after you expect to know.
- Family abroad? Do it live online. With relatives in different countries, the quickest way to tell everyone at once is a video reveal; the online gender reveal guide explains how it works from each phone, free.
Not yet? Our due date calculator shows your current week and when the 10-week and 18 to 22-week windows fall, so you can mark the calendar.
Sources
- American College of Obstetricians and Gynecologists, [Prenatal Genetic Screening Tests (FAQ)](https://www.acog.org/womens-health/faqs/prenatal-genetic-screening-tests): cell-free DNA testing "can be done starting at 10 weeks of pregnancy"; screens for sex-chromosome number problems; the detailed ultrasound is done between 18 and 22 weeks. Checked 26 Oct 2026.
- American College of Obstetricians and Gynecologists, [Ultrasound Exams (FAQ)](https://www.acog.org/womens-health/faqs/ultrasound-exams): at least one standard exam, "usually performed at 18–22 weeks of pregnancy". Checked 26 Oct 2026.
- NHS, [20-week scan](https://www.nhs.uk/pregnancy/your-pregnancy-care/20-week-scan/): offered between 18 and 21 weeks; "you may be asked if you'd like to know the sex of your baby". Checked 26 Oct 2026.
Frequently asked questions
How early can a blood test tell the baby's gender?
From 10 weeks of pregnancy. ACOG says the cell-free DNA test can be done starting at 10 weeks, and it reports the sex chromosomes alongside its main screening results. Earlier samples often have too little DNA and need repeating.
What week can an ultrasound show the gender?
Usually at the anatomy scan, 18 to 22 weeks (18 to 21 in the NHS). Earlier scans are not designed to show it, and the baby's position can hide it even at 20 weeks.
Is the NIPT gender result accurate?
Clinics describe it as highly accurate once there is enough placental DNA in the sample, and it gets more accurate with each week. It is a screening test, so ask your clinic for the figure their lab quotes and let your clinician confirm the result.
Can the hospital refuse to tell us the sex?
Yes. Some hospitals and some countries have a policy of not telling. Ask before the scan, and consider a private scan or the blood test if knowing matters to you.
When should we hold the gender reveal party?
A week or two after you expect the result, so a rescheduled scan or a shy baby doesn't spoil the date. Most reveals happen between weeks 16 and 24.