Yes, it is normal to get milk before the baby is born. This "milk" is actually the colostrum, which is thicker than breast milk itself because it is rich in essential fats and proteins for the baby just born.
Colostrum begins to be produced by the breasts in the end of gestation and you can start leak before delivery. However, this does not happen in all women, which is also absolutely normal.
The hormones responsible for milk production (prolactin and lactogen) are already starting to act from the 2nd trimester of pregnancy. Therefore, it is also normal if some breast fluid comes out during gestation.
However, the production of breast milk actually begins after the baby is born, since high levels of the hormone estrogen in pregnant women prevent production. In addition, the very act of sucking the baby also serves as a stimulus for the release of milk.
