When both parents are Rh negative, there is a high probability that their baby will also be Rh negative. However, it's important to note that the ABO blood type system is independent of the Rh factor. Therefore, the baby could have any blood type (A, B, AB, or O) regardless of the parents' Rh status. It's recommended to consult with your healthcare provider for further information and guidance regarding any specific considerations related to your pregnancy and blood type compatibility.