My husband and I had been married almost a year when we found out we were pregnant. Things were rocky and I was already second-guessing my decision to say "I do". However, I'd always been told it'd be difficult for me to have children and was very excited to find out I was having a baby naturally. Now, almost five months into my pregnancy, I am leaving him, but am worried about custody of our unborn baby. I'm seeking sole physical custody with visitation for the father, and joint legal custody. I think he'll be a good dad, but his situation is unstable, and until he gets his stuff together, I don't want my baby with him more than a couple days a week.
What custody rights does he have, as my husband? We live in Maryland.

Taking into consideration his unstable history, as you say, and you being the baby's mother. The court will probably weigh all the options, but a new baby will always stay with his/her mom until he/she is ready to be handled by another person. Get a lawyer, discuss this with him and tell him what you want. Of course if he is the bio dad then he has rights too.

Tick

What custody rights does he have, as my husband? We live in Maryland.

Until the child is born, he as no rights, as against you, with respect to the child.

As your husband, and when the child is born, as the child's father, he will have the same custody rights you have. This is unless you get an order of separation providing specific terms as to custody, visitation, and support.

If you divorce, again, he will have those rights set out in the divorce decree.

Agree
1. till child is born, there is no child, no custody, nothing,
2. once child is born, he is the father and your husband, so he has every right you have after birth.
3. once born, you can file for custody and offer him visits, he may ask for custody or joint.

It is more and more easy to get joint custody unless one side or the other can be proven to have issues that will effect the care of the child.