Pregnancy Week by Week

Rhesus Disease

Everyone is born with a certain blood type (A, B, AB or 0) and Rhesus factor (Rh positive or Rh negative). If you are Rh negative and your baby is Rh positive, you may become sensitized to the Rhesus factor in your baby's blood, in which case you will produce antibodies to your baby's red blood cells. If this is your first pregnancy, this is not usually a problem.

However, in subsequent pregnancies, if your baby is again Rh positive, these antibodies can cross the placenta and destroy your baby's red cells, causing fetal anaemia. After the birth, the destruction of red blood cells results in high levels of bilirubin (a yellow pigment produced by the breakdown of the blood cells). As well as making your baby appear jaundiced, this can be harmful to his brain.

If both you and the father are Rh negative, there is no danger because your baby will also be Rh negative.

Prevention

One of the greatest success stories in obstetrics is how rare Rhesus disease has become. This is due to the use of Anti-D injections - a blood product - in Rh negative women at risk of Rhesus disease. Anti-D injections prevent Rhesus disease by destroying any fetal cells that enter the mother's circulation before she has a chance to produce any antibodies. Anti-D is routinely given to the mother after the birth (within 72 hours) if a baby is shown to be Rh positive. In recent years, Anti-D

injections have also been given at 28 and 34 weeks. Anti-D is recommended for pregnant Rh negative women after certain events (for example, miscarriage, threatened miscarriage- if this occurs after 12 weeks, or'trauma'to the abdomen, such as a fall or car accident), or after certain procedures that have a risk that fetal blood could cross the placenta.

Symptoms and diagnosis

The severity of Rhesus disease depends on how many of the baby's blood cells have been destroyed. It ranges from mild disease, where the baby is found to be mildly anaemic at birth, to severe disease, where the baby suffers heart failure in the uterus.

A warning sign of Rhesus disease is the presence of Anti-D antibodies in the mother's blood. If you have high levels of Anti-D antibodies, your obstetrician will recommend regular ultrasound monitoring of your baby to keep an eye on his progress. In the past, if there was any suspicion that a baby might be suffering from anaemia, an amniocentesis was performed. Nowadays, this procedure has largely been replaced by looking at the blood flow to the baby's brain. A very high blood flow is an indication that the baby may be anaemic.

Recently, it has become possible to tell whether a baby is Rhesus positive or negative from a blood sample taken from the mother. If, for example, Rhesus disease is suspected, finding that the baby is Rhesus negative is very reassuring.

Treatment

If your baby has Rhesus disease, he can be treated either while he is still in the uterus or after the birth. in the uterus

If your baby seems to be anaemic, a fetal blood sample can be taken. If this confirms anaemia, he can be given a blood transfusion. This procedure may need to be repeated until he is developed enough for delivery.

After the birth

Treatment depends on the severity of your baby's jaundice and anaemia. In mild cases of jaundice, bilirubin levels may respond to light therapy (phototherapy). In more severe cases, an exchange blood transfusion may be necessary.