Rhesus Negative in Pregnancy: Complete Guide

If your blood test results come back showing you're "rhesus negative" (RhD negative), it can sound alarming — but it's a well-understood and closely managed part of routine NHS antenatal care. Around 1 in 6 people in the UK are RhD negative, and with proper monitoring it very rarely causes a problem in this or future pregnancies.

What rhesus negative actually means

Your blood type includes a marker called the RhD factor, which is either present (positive) or absent (negative) on the surface of your red blood cells:

Being RhD negative simply means you don't carry this protein — it's a normal blood type variation, not an illness
It only becomes relevant in pregnancy if your baby's blood is RhD positive, which happens if your baby has inherited the RhD positive gene from their biological father
Your blood group, including RhD status, is checked as a routine part of your booking bloods early in pregnancy
If you're RhD negative, this will be flagged in your maternity notes so your care team can monitor it throughout pregnancy

Why it's monitored — sensitisation explained

The concern with RhD negative pregnancies is a process called sensitisation:

If any of your baby's RhD positive blood cells enter your bloodstream — which can happen during bleeding, a fall, an invasive test, or most commonly during birth — your immune system may recognise them as foreign and start producing antibodies against RhD positive blood
This doesn't usually cause problems in the current pregnancy, since it takes time for antibodies to develop
The risk is in a future pregnancy: if you're carrying another RhD positive baby, those antibodies could cross the placenta and attack the baby's red blood cells, a condition called haemolytic disease of the newborn
This is precisely why anti-D prophylaxis was developed — and why it's been part of routine NHS care for decades, dramatically reducing how often this condition occurs

Anti-D injections: what to expect

Anti-D immunoglobulin is an injection that stops your immune system from forming antibodies in the first place:

It's typically offered routinely during pregnancy (commonly around 28 weeks, sometimes as two doses earlier and later in pregnancy depending on your hospital trust's protocol) and again after birth if your baby is confirmed RhD positive
You may also be offered anti-D after any event where sensitisation could occur, such as bleeding, abdominal trauma, a fall, amniocentesis, or CVS
The injection itself is quick and given in the same way as other routine injections
Anti-D doesn't treat existing antibodies — it only works to prevent them forming, which is why timing matters and it's offered proactively rather than after the fact
Your partner's blood type may also be checked, since if they're also RhD negative, your baby cannot be RhD positive and anti-D may not be needed

Frequently Asked Questions

What does rhesus negative mean in pregnancy?

It means your red blood cells lack the RhD protein — a normal variation found in around 1 in 6 people in the UK. It only matters if your baby's blood is RhD positive, in which case your immune system could form antibodies that affect future pregnancies. Anti-D injections are given routinely to prevent this from happening.

Does being rhesus negative affect this pregnancy?

In most cases, no — sensitisation problems usually only affect subsequent pregnancies, not the current one, because antibodies take time to develop after exposure. Your care team will monitor you closely and offer anti-D at the recommended points to protect future pregnancies. Being RhD negative is very well managed within routine NHS antenatal care.

Will I need anti-D with every pregnancy?

If you're RhD negative and your baby turns out to be RhD positive, yes — anti-D is typically offered in every such pregnancy as routine prevention, regardless of whether you needed it before. If your partner is also RhD negative, your baby cannot be RhD positive, so anti-D usually isn't required in that case. Your midwife will explain what applies to your specific situation based on blood tests.

This article is for informational purposes only and does not constitute medical advice.

Related articles: