Is it haram to find out my baby's gender?

No, it isn't haram to find out your baby's sex from an ultrasound. Most scholars explain that the Quran and hadith speak about the unseen: what no one can know without Allah, like what the child will become. A scan shows a body that Allah has already formed, using a medical tool. Just don't treat it as a promise, and avoid fortune-telling.

What the Quran says about the womb

The Quran lists knowledge that belongs to Allah alone, and it includes the wombs:

إِنَّ ٱللَّهَ عِندَهُۥ عِلْمُ ٱلسَّاعَةِ وَيُنَزِّلُ ٱلْغَيْثَ وَيَعْلَمُ مَا فِى ٱلْأَرْحَامِ "Indeed, Allah [alone] has the knowledge of the Hour. He sends down the rain, and knows what is in the wombs." Quran 31:34

The Prophet ﷺ said the keys of the unseen are five, and that no one knows them but Allah, including what is in the wombs (Sahih al-Bukhari 4697). That worries some new parents when the sonographer asks, "Do you want to know?"

Why a scan is not the same thing

Scholars make a distinction between two kinds of knowledge:

Allah's exclusive knowledge: what the baby will become, whether they will be righteous, how long they will live and what they will earn. Even the doctor can't know any of that.
Knowledge gained through means: after the baby is formed, doctors can observe the body with imaging, the same way they observe a heartbeat or a bone.

The Prophet ﷺ described how, after the early stage of pregnancy, the angel shapes the child and asks whether it will be male or female, and Allah decides (Sahih Muslim 2645). A scan simply sees what Allah has already created. It tells you nothing about the unseen part of the child's life. The sonographer may also be wrong, so say "insha'Allah" and be ready for either answer.

What is forbidden

The prohibited thing is not looking at a scan but claiming to know the unseen through guesswork or magic:

Fortune-tellers and diviners: the Prophet ﷺ said that whoever visits a diviner and asks about anything, his prayers will not be accepted for forty nights (Sahih Muslim 2230).
Horoscopes, tarot and "ancient" gender-prediction tricks that are presented as certain.
Claiming certainty, as if no one can be surprised.

Folk signs, like the shape of the bump or cravings, are just conversation. Don't treat them as knowledge.

Should you find out or wait?

Both are fine. Some parents like to plan and choose names early. Others enjoy the surprise at birth. If knowing helps you prepare, go ahead. If the news might lead to disappointment, wait. Whatever the answer, a child is a gift.

The Prophet ﷺ said that whoever brings up two girls until they grow up will be very close to him on the Day of Resurrection, and he showed it by joining his fingers (Sahih Muslim 2631). Sons and daughters are both blessings. For the celebration side, see Can Muslims have a gender reveal party?

After the scan

Thank Allah, whatever the result, and make dua for a healthy delivery. See What dua do I say for a newborn baby?

Key points

Finding out the sex from an ultrasound is allowed.
Allah alone knows the baby's future, which no scan can show.
Fortune-telling about pregnancy is forbidden.
You may find out or wait; both are fine.

Tip: Whatever the sonographer says, answer with "Alhamdulillah, whatever Allah has given us." It sets a grateful tone for the rest of the pregnancy.