Why do some babies get hair at birth and others don't? For the same reason that some children have curly hair and others have straight hair. It's all about genes - that's the answer🧬 Those babies who are born without hair will soon have it. And those who have their own fluff (or even a real "mane"), the process of hair formation began at 28 weeks of pregnancy. Hair appears on the head, eyebrows, and eyelashes.