Rhesus Factor Issues

The majority of people have rhesus positive (Rh+) blood cells but about 15 per cent of people have rhesus negative (Rh-). During most of life, this isn’t an issue, but it can become so in pregnancy. Here’s why.

If you’re rhesus negative and your partner is rhesus positive, the chances are that your baby will be rhesus positive too. Problems can occur if any of your rhesus negative blood comes into contact with your baby’s rhesus positive blood, because it develops antibodies to the rhesus positive cells which kill them off. This means that if any of your baby’s blood gets into your circulation, you’ll develop antibodies to it and will attack your baby’s red blood cells.

Mostly the different blood types don’t come into contact with each other, but there are situations that can cause it. For example, if, you suffer a bleed, a heavy fall or if you have the amniocentesis diagnostic antenatal test carried out. Although low levels of antibodies won’t usually cause harm to your baby, high levels can cause serious problems. What’s more, once contact has taken place (and unless steps are taken to prevent it) the antibodies will remain in your system. So if you subsequently become pregnant again with another rhesus positive baby, they can attack, damage and even destroy the red blood cells of your baby.

What Can Be Done?

At your early antenatal appointments you’ll have a series of blood tests. One of the tests will determine whether or not you have rhesus negative blood. If you are rhesus negative, your blood will be checked continually during the course of your pregnancy to see if you’re showing any signs of antibodies.

The risk of antibodies developing can be prevented by giving the mother an injection of a substance called anti-D. This clever substance helps prevent any antibodies from forming. In many areas of the UK, this injection is routinely offered to all pregnant women who are rhesus negative, between 28 and 24 weeks of pregnancy and, once given; it’s effective for up to six weeks.

An injection of anti-D is also given after you’ve given birth, when the blood of mum and baby has been analysed, as the blood of mum and baby can often come into contact during the course of giving birth.

In addition, any women with rhesus negative blood who experience bleeding after 12 weeks of pregnancy, or any other situation where blood could come into contact, are given anti-D. Before the 12 week stage there’s only a tiny risk of your baby’s blood entering your bloodstream, so you should be safe during that time. For each subsequent pregnancy, the whole process will be repeated again and you’ll be given more anti-D injections to ensure no problems arise.

Being rhesus negative certainly won’t affect your ability to have a healthy baby. The testing procedures these days are very good and will pick up on whether your blood is an issue or not and help keep you and baby safe and well.