Rhesus incompatibility problems can only arise when a woman’s blood is rhesus negative and her baby’s blood is rhesus positive. This in turn can only happen if the baby’s father’s blood is also rhesus positive. Generally speaking there are no problems during a woman’s first pregnancy with a baby whose blood is rhesus positive. But during childbirth, as opposed to during pregnancy, when there is potential mixing of maternal and foetal blood, the baby’s blood can sensitise the woman to rhesus positive blood and if she has a subsequent pregnancy with a rhesus positive baby there is a risk of haemolytic disease of the newborn. This occurs because the mother will have made antibodies to the rhesus positive blood of the baby, which will react much more strongly in a subsequent pregnancy.

Thankfully the anti-D injection you had immediately after having your first baby will have prevented any risk of this haemolytic disease of the newborn happening. The blood tests you have on a regular basis throughout each pregnancy will make sure there are no antibodies and that no problem exists at all.

Haemolytic disease used to be a big problem in years gone by, but thankfully with modern obstetric intervention, this is something that you can comfortably forget about.
Yours sincerely
The Medical Team

The Rhesus factor is an antigen carried on the red blood cells of most British people. Those with the Rhesus factor are said to be Rhesus positive, those without it are Rhesus negative. If a mother is Rhesus negative and her baby is Rhesus positive, and if by some means some of the baby’s blood cells enter the mother’s circulation, her immune system may respond to what it perceives as a foreign protein by producing antibodies that may destroy the baby’s red blood cells. This can cause a condition known as haemolytic disease of the newborn. From the information you have sent in it sounds as if you are Rhesus negative and your baby is Rhesus positive. If that is the case you and your partner cannot have exactly the same blood group. Your partner would have to be Rhesus positive because it could only be from him that the baby has inherited the Rhesus positive antigen. When people talk about their blood group they are usually referring to the ABO group system (so in that sense you and your partner may be the same if, say, you are both blood group O, or A, or AB etc) but you could still be different with regard to the Rhesus factor.
Yours sincerely
The Medical Team