A, B or AB; and whether or not the baby is Rh neg or Rh pos depends entirely on the person who is positive. Because mom is AB-, that means she is neg-neg. and can only pass on the Rh neg. If Dad is pos-pos, then that means he can only pass on the Rh pos, and that means all babies from that union will be Rh pos. If Dad is pos-neg, then that means there is a 50% chance baby will be Rh pos.
Whether or not you get the RhoGam shot at all has no affect on what blood type the baby has; it's to keep your body from making antibodies if the baby's blood cells somehow enter your bloodstream during pregnancy or the birth. Most consider it to be necessary, a low-risk protection for any future babies you may carry. Others decide to either get only the postpartum dose of RhoGam once the baby's blood type is known to be positive, or to forgo RhoGam entirely. Please PM me if you would like to find out more about being an Rh neg mama.
at 10:09 PM on May. 28, 2009