When Can You Find Out the Sex of Your Baby?

When can you find out the sex? Every method compared

For most people in the UK, the answer is the 20-week scan, if the baby is lying well and the hospital's policy allows it. Earlier routes exist, but they are either not offered on the NHS, not reliable yet, or only available for medical reasons.

Can you find out the sex at the 20-week scan?

Usually, yes — but it depends on your hospital and on your baby's position. The NHS states that finding out the sex "is not offered as part of the national screening programme", that you may be able to find out at the 20-week scan depending on hospital policy, and that you should tell the sonographer at the start if you want to know.

The national screening leaflet puts it plainly: "Finding out the sex of your baby is not the purpose of this scan, but most hospitals will tell you if it's easy to see. You will not be offered another scan if the sex of your baby is not seen." The NHS adds that some hospitals have a policy of not telling, and that the sonographer cannot be 100% certain — if the baby is lying awkwardly, it may be difficult or impossible to tell.

When a sonographer is confident, the call is very accurate. In a 2014 Australian study that followed 640 fetuses scanned in a private practice, every sex prediction made after 14 weeks was correct. The rest of that week is covered in 20 weeks pregnant.

Can you find out the sex at the 12-week scan?

Not on the NHS, and early guesses are much less reliable. In the same 2014 study, sonographers' predictions at 11 to 14 weeks were right 75% of the time overall, rising to 91% when scans where no guess could be made were excluded. Before 12 weeks the success rate was 54%, and boys under 13 weeks were the most likely to be called wrongly or not at all. The authors concluded that predictions before 12 weeks "should be discouraged".

One early method, reading the angle of the genital tubercle on the scan, is popularly called the nub theory and has its own page.

Can a blood test tell you the sex?

Yes, but not the NHS one. The NHS screening handbook says the NIPT it offers screens for Down's, Edwards' and Patau's syndromes only "and will not screen for other chromosomal conditions or assess the baby's sex". On the NHS, NIPT is offered after a higher-chance screening result — see NIPT and what it can tell you and screening tests in the UK.

In the US, ACOG describes cell-free DNA testing as available from 10 weeks, with results in about a week, and says it can screen for problems with the number of sex chromosomes. These tests work on cell-free DNA from the pregnancy circulating in your blood, which the NHS handbook says can be detected from as early as 5 weeks.

How accurate are blood tests for the sex?

A 2011 meta-analysis in JAMA, pooling 57 studies and more than 6,500 pregnancies, looked at tests that search the mother's blood or urine for Y-chromosome DNA. A Y signal means a boy; no signal is read as a girl. Its results by stage of pregnancy:

The pattern matters. An early "girl" result is the one most likely to be wrong, because a boy whose DNA was missed looks like a girl. The authors concluded that tests "performed before 7 weeks' gestation" and tests using urine "were unreliable".

Can amniocentesis or CVS tell you the sex?

These tests analyse your baby's chromosomes, but they are offered for medical reasons, not curiosity. The NHS offers amniocentesis if a screening test shows a higher chance of a condition, if you have had a previous pregnancy affected by one, or if you, the baby's father or a close relative has one. It is usually done between 15 and 20 weeks, and the NHS puts the risk of miscarriage at 1 in every 200 pregnancies. Amniocentesis and CVS explains both tests.

Can you choose the sex with IVF?

In the UK, only to avoid a serious condition. The Human Fertilisation and Embryology Act 1990 states that a clinic licence "cannot authorise any practice designed to secure that any resulting child will be of one sex rather than the other", except where there is a particular risk of a serious disability, illness or medical condition that affects only one sex, or one sex significantly more than the other. Preimplantation genetic testing covers what embryo testing can and cannot be used for. Rules differ between countries, so check the law where you are treated.

What about the old wives' tales?

Ring tests, carrying high or low, cravings and heart rate are folklore rather than tests. If you are curious about them anyway, old wives' tales for boy or girl goes through each one and what studies have found.

Frequently asked questions

Can the NT scan tell the gender?

The nuchal translucency measurement is part of Down's syndrome screening and is not designed to show the sex, and the NHS does not offer sex determination at this scan. In a 2014 study, sonographers' early guesses at 11 to 14 weeks were right 75% of the time, and only 54% before 12 weeks.

Does NHS NIPT tell you the sex?

No. The NHS screening handbook states that the NIPT offered within the NHS programme will not assess the baby's sex; it screens only for Down's, Edwards' and Patau's syndromes. Private and US cell-free DNA tests can look for Y-chromosome DNA, but whether a test reports sex depends on the provider.

Can the 20-week scan get the sex wrong?

It can, mainly when the view is poor. The NHS says a sonographer cannot be 100% certain and that an awkward position can make it difficult or impossible to tell. When sonographers did commit to a prediction after 14 weeks in a 2014 Australian study of 640 fetuses, every one was correct.

At what week can you find out the gender?

Blood tests that look for Y-chromosome DNA are unreliable before 7 weeks and detected about 95% of boys from 7 to 12 weeks in a 2011 meta-analysis; in the US, ACOG describes cell-free DNA testing from 10 weeks. On the NHS, the usual chance is the 20-week scan, between 18 and 21 weeks, if hospital policy allows.