Effects of Rhesus factor in an unborn kid

Dear Dr Ombeva,

I am a B- and my husband is B+ blood group. Do you think I will be able to give birth to a normal healthy baby? I am worried because a friend who is O- gave birth and the baby died, and the doctor told her it is because the husband is B+. What can I do to avoid the same fate?

Anxious

Dear Anxious,

We each have a blood group, either A, B, AB or O; that is either positive or negative, depending on whether they have inherited an Rh (Rhesus) factor; where people with a Rh factor are Rh positive while those without are Rh negative.

The Rh factor can cause problems if you (woman) are Rh negative and your foetus is Rh positive - called Rh incompatibility. These problems usually do not occur in a first pregnancy, but they can occur in a later pregnancy.

When an Rh-negative mother’s blood comes into contact with blood from her Rh-positive foetus, it causes the Rh-negative mother to make antibodies against the Rh factor. These antibodies attack the Rh factor as if it were a harmful substance.

A person with Rh-negative blood who makes Rh antibodies is called “Rh sensitised.” If the mother and father are both Rh negative, the baby also will be Rh negative. When a woman has a negative blood group, for example O negative, and her husband has positive blood group, for example O positive; the children may be either positive or negative blood group.

Each time she gives birth, the blood group of baby must be checked immediately after birth. If the baby has a positive blood group like the father, the mom must receive an injection called anti-D; within 72 hours. If the baby has a negative blood group like the mother, then anti-D is NOT needed.

The injection protects the mother’s future Rhesus positive babies from the effect of sensitisation of the mom’s negative rhesus blood by the current new-born baby’s Rhesus positive blood (because the effects are so bad and can kill the future Rhesus positive baby).

In an event where the baby is born rhesus positive and mom is negative and didn’t get the injection after 72hrs, we do the test called the Coombs test, to determine whether the mom got sensitised or not. If the mother and father are Rh positive, then it doesn’t matter whether the father is positive or negative because the mother has the Rhesus itself, so cannot get sensitised, and all her pregnancies are safe.

In addition, any rhesus negative mother should also receive anti-D after pregnancy loss at any time during the pregnancy whether induced abortion or spontaneous loss.

— Dr Ombeva Malande is a paediatric and child health expert