I started leaking milk at 21 weeks and I think you can start working maternity bras whatever you feel you need it im still using normal bras just ones without whires and went up a bra size
You might see any sign of milk coming in til after delivery of your baby
Breast milk doesn't come out until a couple days after baby is born. You may have some drops here and there of some colostrum. BUT nothing that you need a bra for.
Ftm at 33 weeks and no signs of milk only colostrum. I'm still in my old bras but my breasts haven't grown that much. An article I read said to wait till about the last month before you get bras as your breasts continue to grow and make sure you're being properly sized by a perfessional. Motherhood maternity store is a good place, so I've heard. They can help you get sized and get a proper bra, or lead you in the right direction if they're too expensive.