All babies begin to grow in the womb in exactly the same way. Many people think that all unborn babies begin life in the womb as females, however this is not quite right – we actually all begin life without a gender!
We spend the first 6-7 weeks of life developing in exactly the same way as each other and this non-gendered early foetus has nipples! When an unborn baby reaches week 6-7 of development, it begins to develop into a male or female, depending on which chromosomes it has. If it has an X and a Y chromosome, instructions (called genes) on the Y chromosome cause it to develop into a male. If it has two X chromosomes (and no Y chromosome), it will develop into a female. Because the nipples have grown before the baby develops into a boy or girl, they are present in both genders.
When babies are born, and all through childhood, the nipples are still present and look identical between boys and girls. It is only during puberty in females, that breast tissue begins to develop and female nipples start to appear different to males. And then of course, when a female has children, the hormones from pregnancy encourage milk to develop in the breasts and the nipples finally have a role!