Although rhesus disease is rare and most cases are successfully treated, there are some risks to both unborn and newborn babies.

If rhesus disease causes severe anaemia in an unborn baby, it can lead to:

• foetal heart failure
• fluid retention and swelling (foetal hydrops)
• stillbirth

Blood transfusions given to a baby in the womb (intrauterine transfusions [IUT]), can be used to treat anaemia in an unborn baby. However, this treatment also carries some risks of complications. It can lead to an early labour that begins before the 37th week of pregnancy and there's a risk of miscarriage or stillbirth.

Rhesus disease causes a build-up of excessive amounts of a substance called bilirubin. Without prompt treatment, a build-up of bilirubin in the brain can lead to a neurological condition called kernicterus. This can lead to hearing loss, blindness and vision loss, brain damage, learning difficulties, or even death.

Treatment for rhesus disease is usually effective in reducing bilirubin levels in the blood, so these complications are uncommon.

The risk of developing an infection from the blood used in blood transfusions is low, because all the blood is carefully screened. The blood used will also be matched to the baby's blood type, so the likelihood of your baby having an adverse reaction to the donated blood is also low.

However, there may be a problem with the transfusion itself. For example, the tube (catheter) used to deliver the blood can become dislodged, causing heavy bleeding (haemorrhage) or a blood clot.

Generally, the risks associated with blood transfusions are small and don't outweigh the benefits of treating a baby with anaemia.