When can you find out your baby's sex? Ultrasound, NIPT and old wives' tales

“Girl or boy?” is one of the most common questions in pregnancy. Being curious is completely natural; some families want to know weeks ahead, others prefer to keep it for the birth. Both choices are perfectly fine.

How is sex determined?

Sex is set by the chromosomes formed at conception. The external genitals develop later in pregnancy, so in the very early weeks they cannot be told apart on ultrasound. When they can be seen depends on the baby's position, the quality of the equipment and the experience of the person doing the scan.

When can ultrasound show it?

It is usually seen at the detailed ultrasound in the second trimester. Sometimes an earlier guess is possible, but early guesses are less certain. If the baby has turned its back or crossed its legs, a clear view may not be possible and the next check will try again. For more, see “Detailed ultrasound” in the guide.

Can NIPT tell you?

NIPT is a screening test that examines fragments of the baby's DNA in the mother's blood, and its results can include the baby's sex. Its main purpose is screening for certain chromosome differences; sex is a side result. Whether this information is shared varies between centres and countries, so it is good to ask beforehand. For more, see “NIPT and triple-quadruple tests”.

What do the old wives' tales say?

Many beliefs have been passed down through generations and most are shared with love and curiosity. Still, none have a scientific basis:

• Belly shape: A pointed or round belly does not show sex; it depends on muscle tone, womb position and the baby's position.
• Cravings: Wanting sweet or sour food is not linked to the baby's sex.
• Ring or string test: The swing direction comes from tiny movements of the hand.
• Severity of nausea and skin changes: These vary with hormones and from person to person.
• Heart rate: A baby's heart rate does not reveal sex.

Having fun with these beliefs is fine; just do not treat the outcome as fact.

What can you do while you wait?

1. Talk with your partner about whether you want to know.
2. Tell your doctor or sonographer beforehand whether you want to know or not.
3. If the view is not clear, do not worry; note it for the next check.
4. If you plan a reveal celebration, ask for the result in a sealed envelope handed to someone else.
5. Be ready with names for both possibilities.

After all

Knowing or not knowing does not change your bond with your baby. A healthy pregnancy and regular follow-up are what matter.

Sharing the news

Whom you tell, and when, is entirely up to you. Some families celebrate, others keep it to themselves. Elders or friends may guess and say things like “that is a girl's belly”; smiling and moving on is the easiest way. Most comments come with good intentions, but the decision and the feeling are yours.

When to contact your doctor

• If you do not understand a finding reported on the scan, ask your doctor to explain.
• If results are not what you expected or the view was unclear, ask your questions at the next check.
• If you struggle to understand a test result, request an appointment.
• If there is heavy bleeding or severe pain, call 112 (in Turkey) or your local emergency number.

Frequently asked questions

When is sex known for certain? There is no exact week; it is often seen at the detailed scan but depends on the baby's position.

Can the ultrasound be wrong? Rarely, there is a margin of error, especially in early weeks.

What if I do not want to know? Politely say so at the start of the scan.

This article is general information; your doctor can give details.