Many parents look forward to finding out whether they are expecting a boy or a girl. A gender scan from 16 weeks is one of the most popular ways to find out, and a blood test can now give you an answer even earlier.
This guide explains how accurate a gender scan is, what the 12-week scan can show, and how the NIPT gender test and NIPT compare.
Key points
- From 16 weeks, your baby's external genitalia can usually be seen clearly, and a gender scan is very accurate when your baby is in a good position.
- At a detailed scan at 12 to 13 weeks, your baby's sex can be determined from the angle of the genital tubercle, sometimes called the nub, with 99 to 100% accuracy.
- An NIPT gender blood test from 7 weeks, or NIPT from 10 weeks, can tell you your baby's sex earlier, with high accuracy.
- In twins, a blood test can show whether at least one baby is a boy, but a scan is needed to tell which baby is which.
What is the early anatomy and gender scan at 16 weeks?
By 16 weeks, your baby's external genitalia have developed enough to be seen directly on ultrasound. Our early anatomy and gender scan at 16 to 18 weeks is a consultant-led scan that assesses your baby's growth, anatomy and development, and tells you your baby's sex if you would like to know.
What do we advise at The Pregnancy Clinic?
Finding out your baby's sex is an exciting moment for many parents. There are, however, a few things we recommend you consider.
- There is no need to wait until 16 weeks. Your baby's sex can be determined at a detailed scan at 12 to 13 weeks with 99 to 100% accuracy, together with an early assessment of your baby's anatomy (see below).
- A blood test can tell you earlier. The NIPT gender test can determine your baby's sex from 7 weeks. If you are having NIPT for common chromosomal conditions from 10 weeks, finding out your baby's sex is a free optional add-on.
- Your baby's health comes first. Although finding out your baby's sex is important and exciting, it is more important to make sure that your baby's growth and development are normal. There have been reported cases where a basic scan by a non-specialist operator determined the baby's sex but missed a major abnormality.
This is not an ideal situation. At The Pregnancy Clinic, we therefore always carry out a detailed assessment of your baby's growth, anatomy and development, as well as determining your baby's sex. This is best done at 12 to 13 weeks, but can also be done at 16 weeks.
How accurate is a gender scan at 16 weeks?
When your baby is in a suitable position and the view is clear, a gender scan from 16 weeks is very accurate. If your baby is lying with the legs crossed, or facing away, it may not be possible to see clearly straight away, and the scan may take a little longer or a further look may be needed. We only tell you your baby's sex when we are confident of what we can see.
At the 20-week scan, the genitalia are checked again as part of the detailed assessment of your baby's anatomy.
Can the 12-week scan tell the baby's sex?
At 11 to 14 weeks, the genital area looks similar in boys and girls. The sex can be suggested from the angle of the genital tubercle, or nub. In boys it points upwards at an angle of more than 30 degrees, and in girls it lies more parallel to the spine.
In a study from the Fetal Medicine Foundation, the accuracy increased from about 70% at 11 weeks to 99% at 12 weeks and 100% at 13 weeks. Most errors at 11 weeks were boys who were thought to be girls. If your baby's position does not allow a clear view, the sex can be confirmed at a later scan.
For further information, read: The 12-Week Scan: What Can It Tell You?
Can NIPT tell you earlier?
From early pregnancy, small fragments of DNA from the placenta circulate in your blood. A blood test can look for DNA from the Y chromosome: if it is present, your baby is a boy, and if it is absent, your baby is a girl.
- NIPT gender test from 7 weeks: tells you your baby's sex only. It is carried out after a scan has confirmed a continuing pregnancy. Tests performed from 7 weeks are highly accurate, whereas testing before 7 weeks is less reliable.
- NIPT from 10 weeks: screens for Down's, Edwards' and Patau's syndromes and can also report your baby's sex as a free optional add-on, if you would like to know. Some extended NIPT panels also screen for sex chromosome conditions, such as Turner syndrome or Klinefelter syndrome. These are optional and best discussed with your consultant beforehand.
For further information, read: NIPT vs Combined Screening: Which Test Should I Choose?
How do the options compare?
| Test | When | What it tells you | Accuracy |
|---|---|---|---|
| NIPT gender test | From 7 weeks | Baby's sex only | Very high from 7 weeks |
| NIPT | From 10 weeks | Baby's sex, plus screening for Down's, Edwards' and Patau's syndromes | Very high |
| 12-week scan | 11 to 14 weeks | Sex suggested from the nub | About 70% at 11 weeks, rising to almost 100% by 13 weeks |
| Gender scan | From 16 weeks | Sex seen directly, with an early check of your baby | Very high when the view is clear |
When results may be less reliable
- Twins: a blood test can show whether at least one baby is a boy, but it cannot say which twin or whether both are boys. A scan is needed for this.
- Vanishing twin: DNA from a twin that has stopped developing may remain in the blood for some weeks.
- Very early testing: a blood test before 7 weeks increases the chance of no result or an incorrect result.
- Rare situations: some rare medical conditions, or a bone marrow or organ transplant from a male donor in the mother, can affect blood test results.
Which option is right for me?
If you would like to know as early as possible, the NIPT gender test from 7 weeks is the earliest reliable option. If you are planning screening for chromosomal conditions, NIPT from 10 weeks can give you both results from one blood sample.
If you would prefer to see your baby and find out on a scan, a gender scan from 16 weeks, as part of an early anatomy scan, gives a clear answer in most cases, together with a check of your baby's development.
Related pregnancy guides
Frequently asked questions
When can you find out the baby's sex on a scan?
From 16 weeks, the baby's external genitalia can usually be seen clearly on ultrasound. At the 12-week scan, the sex can only be suggested from the nub.
How accurate is a gender scan at 16 weeks?
When the baby is in a suitable position and the view is clear, a gender scan from 16 weeks is very accurate.
Can the 12-week scan tell the baby's sex?
The sex can be suggested from the angle of the genital tubercle, or nub. Accuracy rises from about 70% at 11 weeks to almost 100% by 13 weeks, but a clear view is not always possible.
How early can a blood test tell the baby's sex?
The NIPT gender test can tell you your baby's sex from 7 weeks, after a scan has confirmed a continuing pregnancy.
Does NIPT tell you the baby's sex?
Yes. NIPT from 10 weeks can report your baby's sex, if you would like to know, alongside screening for Down's, Edwards' and Patau's syndromes.
Can a blood test tell the sex of twins?
It can show whether at least one baby is a boy, but not which twin or whether both are boys. A scan is needed for this.
Finding out your baby's sex at The Pregnancy Clinic
You can find out your baby's sex with our consultant-led early anatomy scan from 16 weeks, with the NIPT gender test from 7 weeks, or with NIPT from 10 weeks.
Every blood test is carried out alongside a consultant-led scan to confirm your dates and check on your baby.
Book an early anatomy scan →The Pregnancy Clinic provides planned appointments only. If you have pain, bleeding or any other urgent concern, please contact your local NHS maternity unit, Early Pregnancy Unit, NHS 111 or your GP.
Clinical references
- Akolekar R, Farkas DH, VanAgtmael AL, Bombard AT, Nicolaides KH. Fetal sex determination using circulating cell-free fetal DNA (ccffDNA) at 11 to 13 weeks of gestation. Prenat Diagn 2010;30:918–23
- Efrat Z, Akinfenwa OO, Nicolaides KH. First-trimester determination of fetal gender by ultrasound. Ultrasound Obstet Gynecol 1999;13:305–7
- Devaney SA, Palomaki GE, Scott JA, Bianchi DW. Noninvasive fetal sex determination using cell-free fetal DNA: a systematic review and meta-analysis. JAMA 2011;306:627–36
- NHS — 20-week scan