Rh Negative Blood Group in Pregnancy: Anti-D Explained

Most people are Rh positive. If your blood group is Rh negative, it does not make you unwell, but it needs a little planning in pregnancy. A simple injection called anti-D is given at the right times to protect your future babies.

This guide explains what Rh negative means, why testing is done, when anti-D is given and what questions to ask your doctor.

What Does Rh Negative Mean?

The Rh factor is a protein on the surface of red blood cells. Cleveland Clinic says about 85 percent of people have it (Rh positive) and about 15 percent do not (Rh negative). You inherit your type from your parents, and it does not affect your general health. In pregnancy it matters only when your blood mixes with your baby's.

Your blood group, such as A negative or O negative, includes both the ABO group and the Rh type, so your report may show a plus or minus sign after the letter.

Why Can It Cause Problems?

Problems arise only when a mother is Rh negative and her baby is Rh positive. In that case:

• A small amount of the baby's blood can enter the mother's blood, especially around delivery.
• The mother's immune system may treat the baby's Rh positive cells as foreign and make antibodies.
• In a later pregnancy with an Rh positive baby, those antibodies can cross the placenta and break down the baby's red blood cells.

MedlinePlus explains that this can cause newborn jaundice and, in severe cases, serious complications. Cleveland Clinic lists anaemia in the baby, jaundice and, rarely, heart failure or stillbirth. Mild cases often need no treatment, and many babies recover fully. Our guide to newborn jaundice explains how jaundice is treated.

Complications usually do not occur in a first pregnancy, because antibodies typically form only after delivery. That is why the injection is given even in the first pregnancy: it protects the next one.

Why Blood Group Testing Matters

Cleveland Clinic says every pregnant woman has a blood test for Rh status in the first trimester, usually at the first antenatal visit. That is why your blood group should be recorded early.

• If you are Rh negative, a second test checks whether you have already made antibodies.
• If there are no antibodies, anti-D is planned.
• If antibodies are present, the anti-D injection will not help, and your doctor will monitor the baby closely.

See our first trimester guide and month-by-month checkups for when tests happen.

Does Your Partner Need Testing?

The baby's Rh type depends on both parents. Cleveland Clinic explains:

• If you are Rh positive, there is no Rh risk, whatever your partner's type.
• If you and your partner are both Rh negative, the baby will be Rh negative, so there is no risk.
• If you are Rh negative and your partner is Rh positive, the baby could be either, so the risk is treated as high.

Because of this, doctors often ask for your partner's blood group. MedlinePlus says the injection is given in the second trimester if the father is Rh positive or his blood type is unknown. Some hospitals can also test the baby's Rh type from the mother's blood, and the Cambridge hospital page describes this. Availability varies, so ask your doctor.

Anti-D Injection: When Is It Given?

Timing differs between sources, so guidelines vary. Here is what they say:

• **During pregnancy:** Cleveland Clinic says typically around 28 weeks. Cambridge University Hospitals describes routine anti-D at 28 to 30 weeks. MedlinePlus says in the second trimester.
• **After birth:** If the baby is Rh positive, another injection is given within 72 hours of delivery, according to Cleveland Clinic and Cambridge. MedlinePlus says within a few days.
• **After events that can mix blood:** Cleveland Clinic lists vaginal bleeding, tummy injury, miscarriage or ectopic pregnancy, amniocentesis and chorionic villus sampling, turning a breech baby, and delivery. Cambridge says injections after such events should be given within 72 hours.

Tip: Keep a note of every date you receive anti-D in your antenatal file. Show it at every visit and again at delivery.

What to Expect

An anti-D injection is given into a muscle, as described for the upper arm by Cambridge. Cambridge University Hospitals says soreness at the injection site is common and may last a day or two, mild fever, headache or rash are uncommon, and a serious allergic reaction is very rare. You may be asked to wait for about 20 minutes afterwards. After the birth, a sample of the baby's cord blood confirms the baby's blood group so that your doctor can decide whether you need the postnatal injection. Your doctor will decide the right product and amount for you, and this article does not give doses.

Myths and Facts

• **Myth:** Rh negative women cannot have healthy babies. **Fact:** Most have healthy babies, because anti-D prevents the problem. Cleveland Clinic says Rh disease has become infrequent since it was introduced.
• **Myth:** The injection is only needed after the first baby. **Fact:** It is needed in every pregnancy.
• **Myth:** If the first pregnancy was fine, I am safe. **Fact:** Risk rises in later pregnancies if protection was missed.
• **Myth:** Rh negative is a disease. **Fact:** It is simply a blood type.

When to be cautious: If you have vaginal bleeding, a fall or blow to the tummy, or a miscarriage, tell your doctor that you are Rh negative the same day, because you may need an anti-D injection soon.

When to See a Doctor

Contact your doctor promptly if you:

• Do not know your blood group or have lost the report
• Are Rh negative and have bleeding, pain or an injury to the tummy in pregnancy
• Are Rh negative and had a miscarriage or ectopic pregnancy. See miscarriage causes and recovery and bleeding in early pregnancy
• Have just delivered and are not sure whether you were given anti-D
• See your newborn turning yellow in the first days

For urgent issues, see our emergency page.

Talk to a Doctor

If you are Rh negative, share your blood group with your doctor at the start of every pregnancy. Book an appointment or call +91 944 103 0587. Learn about antenatal check-ups and postnatal and newborn care.

This article is for general awareness and is not a substitute for a doctor's advice.