People with rhesus positive blood have a protein called 'D antigen' on the surface of their red blood cells, and they are said to be 'RhD positive'. People without D antigen are known as 'RhD negative'. Around 90% of pregnant women are 'RhD positive'.

Rhesus disease, also known as haemolytic disease of the newborn (HDN), is a condition where antibodies in a pregnant woman's blood attack her baby's blood cells. There are three circumstances that have to be in place before this can occur: firstly, the mom-to-be has to have rhesus-negative (RhD negative) blood; secondly, the baby has to have rhesus-positive (RhD positive) blood; thirdly, the mother has to have been exposed to rhesus-positive blood, either through a blood transfusion or by having had a previous pregnancy with a rhesus-positive baby. This can cause the production of antibodies, which can attack any subsequent rhesus-positive baby in the womb.

Rhesus incompatibility doesn't have any adverse effect in a first pregnancy, because the antibodies aren't already present in the mom. If there's Rhesus incompatibility in a subsequent pregnancy, though, there's a serious risk that the antibodies that might have been produced meanwhile will identify the baby as a 'foreign body' which they will then try to reject by breaking down the baby's blood cells.

Rhesus disease is pretty rare in the US since a routine anti-D injection was introduced for women who are rhesus-negative. It's given twice, at 28 weeks and 34 weeks of pregnancy, to prevent production of the harmful antibody. If this is your first pregnancy, after delivery, your baby's rhesus status will be checked from an umbilical cord blood sample. If your baby is rhesus-positive, you'll be given another injection within 72 hours. This will stop you building up antibodies between the delivery and any subsequent pregnancy with another rhesus-positive baby. The injections have reduced number of cases of rhesus disease by 90%, but severe cases can lead to stillbirth (when a baby dies in the womb).

What are the symptoms of Rhesus disease?

Rhesus disease only affects the baby and is characterized by jaundice and anaemia in a newborn. The condition needs specialist treatment in a neonatal unit to prevent complications such as learning difficulties, blindness and deafness developing.

What are the treatments and remedies of Rhesus disease?

Babies who develop rhesus disease while still in the womb, can be given one or more intrauterine foetal blood transfusions (IUT). In newborns, if symptoms are mild, no treatment is usually necessary, but in more severe cases treatment includes phototherapy (treatment with UVB light) and, possibly, blood transfusions.

This guide

This article is not meant to substitute medical advice provided by a practicing medical professional - if you have any concerns, contact your physician immediately.