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Pregnancy and birth

Rhesus disease and anti-D in pregnancy

Rhesus disease, now usually called haemolytic disease of the fetus and newborn (HDFN), happens when a D-negative mother develops antibodies against a D-positive baby's red blood cells. Routine blood-group screening picks out women who need anti-D injections, and treatment is usually very effective.

Last checked: 2026-10-03

Key facts

At a glance.

  • What it is

    A rare blood disorder where the mother's antibodies break down the baby's red blood cells.

  • Who is affected

    A D-negative mother carrying a D-positive baby who has already been exposed to D-positive blood.

  • Screening

    A blood test at the 8 to 12 week antenatal appointment shows your blood group and whether you are D negative.

  • Prevention

    Injections of anti-D are offered to stop antibodies forming.

  • Outlook

    The NHS says the risk of complications is low because treatments are usually very effective.

What the D in rhesus means

Everyone's red blood cells carry a blood group, and many people also carry a protein called the D antigen. If you have it you are D positive, which is the majority; if you do not, you are D negative. Being D negative is not an illness and causes no symptoms. It only matters in pregnancy, when the baby inherits a D-positive blood group from the father.

How the disease develops

The NHS explains that the problem starts when a D-negative mother's immune system meets D-positive blood. This can happen through a blood transfusion or a previous pregnancy with a D-positive baby. Once the mother has made antibodies, they cross the placenta in a later D-positive pregnancy and attack the baby's red blood cells, causing anaemia and a build-up of the pigment that causes jaundice.

A first pregnancy is rarely affected, because the sensitisation usually happens around the time of delivery, although events during pregnancy can also cause it. That is why prevention in every D-negative pregnancy is important.

Routine screening in pregnancy

At the booking appointment, at around 8 to 12 weeks, a blood test shows your blood group. If you are D negative, further testing looks for antibodies. If the baby's blood group is checked and it is D positive, the team assesses whether HDFN is a risk. Women who already have antibodies are managed by a specialist team and have regular monitoring.

Anti-D injections

If there is a risk, the NHS says you will usually be offered injections to stop you developing antibodies. The injection contains anti-D immunoglobulin made from donated blood plasma, and it works by clearing D-positive baby cells from your blood before your immune system reacts to them. The NHS page on prevention refers readers to a leaflet from NHS Blood and Transplant on receiving anti-D in pregnancy, which sets out the timing in detail.

Ask your midwife which of your pregnancy events counted as a possible sensitising event, such as bleeding, a fall or an invasive test, and whether you should have had an extra dose. If you ever have bleeding in pregnancy, tell the team that you are D negative.

What happens if the baby is affected

In pregnancy, treatment can include blood transfusions given to the baby and weekly immunoglobulin treatments for the mother to prevent the baby from becoming anaemic. If anaemia develops late, early delivery by caesarean may be recommended.

After the birth

A baby with HDFN can be pale, breathe quickly and feed poorly because of anaemia, or have yellow skin and eyes, dark urine and drowsiness because of jaundice. Treatment includes phototherapy, which uses light on the skin to break down bilirubin, and exchange transfusion, in which the baby's blood is replaced with donated blood. Serious cases may need neonatal intensive care. Follow-up blood tests check for late anaemia.

Frequently asked

Questions people ask.

Quick, plain-English answers to the questions we hear most.

  • What does D negative mean?

    Your red blood cells lack the D antigen. It is harmless on its own and relevant mainly in pregnancy.

  • Will my first baby be affected?

    It is uncommon, because antibodies usually develop after sensitisation, often around birth, and affect later pregnancies. Prevention is still offered each time.

  • What is in the anti-D injection?

    Anti-D immunoglobulin, a medicine made from antibodies in donated blood plasma.

  • When do I get anti-D?

    The NHS says injections are offered when there is a risk. The timing is set out in the NHS Blood and Transplant leaflet and your maternity team will explain your schedule.

  • Should I tell staff if I bleed in pregnancy?

    Yes. Say that you are D negative, because bleeding can be a sensitising event and treatment may be needed.

  • Is rhesus disease the same as ABO incompatibility?

    No. ABO incompatibility between mother and baby is a different blood-group mismatch and is usually milder.

  • Can the baby be treated before birth?

    Yes. Blood transfusions for the baby and immunoglobulin treatment for the mother are used, and early delivery may be advised if anaemia develops.

  • What are signs of anaemia and jaundice in a baby?

    Pale skin, fast breathing and tiredness for anaemia; yellow skin and eyes, dark urine and poor feeding for jaundice.

  • Is the outlook good?

    Yes for most families. The NHS says the risk of complications is low because treatments are usually very effective.

Where this comes from

Sources and checking.

This guide is for information, not medical advice.

Your GP or consultant knows your history and can tell you which parts apply to you. If your symptoms are severe, rapidly worsening, or come with red-flag features, seek urgent medical care. Figures and availability change, so treat them as a guide and confirm with the provider.

Published 2026-10-03, next review 2027-10-03.

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