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Mother-to-baby transmission of HIV
   Last updated: 29.04.05
 
This information is also included in the booklet HIV and Children in this series.
If you are HIV-positive and pregnant, or thinking about having a baby, it is important to know that you can pass on HIV to your baby during pregnancy, or during delivery, or by breast-feeding.

However, anti-HIV treatment can greatly reduce the risk of you passing on HIV infection to your baby. In addition, many mothers choose to have their babies delivered through an operation (a caesarean birth) as this can further reduce the risk. Exclusive formula feeding is strongly recommended for all babies born to HIV-positive mothers in the UK. Using these methods it’s possible to reduce the risk of mother-to-baby transmission of HIV from about 25% to less than 1%.

A number of factors can make it more likely that you will pass on HIV to your baby. These include:
  • Having a high HIV viral load or a low CD4 cell count.

  • Your waters breaking more than four hours before delivery.

  • Having an untreated sexually transmitted infection or bacterial vaginosis when you give birth.

  • Using recreational drugs, particularly injected drugs, during pregnancy.

  • Having a vaginal delivery (rather than a caesarean delivery) when you have a detectable viral load.

  • Having a difficult delivery, for example if forceps need to be used.

  • If you breastfeed.


Preventing mother-to-baby transmission – with anti-HIV drugs
Taking anti-HIV treatment can dramatically reduce the risk of you passing on HIV to your baby.

There are two different ways in which these drugs can act.

First, they reduce your viral load - the level of virus in your blood - so your baby is exposed to less of the virus while in the womb and during childbirth. The aim of HIV treatment is to get, and keep, your viral load below 50 copies/ml. This is often referred to as an undetectable viral load.

Second, the drugs may cross the placenta and enter your baby's body, where they can prevent the virus from ever taking hold. Newborn babies are given a short course of anti-HIV drugs after they have been born when their mother is known to be HIV-positive.

Two drugs have been shown to be very effective at preventing a mother from passing on HIV to her baby in the second of these ways. These are the nucleoside analogue (NRTI) AZT, and the non-nucleoside (NNRTI) nevirapine. It is likely that other drugs are also very effective, but they have not been tested as extensively.

The way in which these drugs are used (AZT on its own, or AZT or nevirapine in combination with other anti-HIV drugs) will depend on how much damage HIV has done to your immune system, and the point in your pregnancy when HIV is diagnosed.

In the UK, and other countries where there is access to a full range of anti-HIV drugs for treatment, nevirapine should not be used by itself (as monotherapy) to prevent mother-to-baby transmission of HIV because resistance to the drug can rapidly develop if it is used in this way. Using it alone might limit your ability to benefit from nevirapine or related drugs in future, when you need them to protect your own health.

In good health?
If you have a good CD4 cell count and low HIV viral load and are not ill because of HIV, then UK guidelines recommend that you start taking AZT in the final three months (third trimester) of your pregnancy. You will also need to have an intravenous dose of AZT during delivery and have a caesarean rather than vaginal delivery. Another option is to take a short course of HAART (three anti-HIV drugs) during the last few months of pregnancy in order to get your viral load down to below 50 copies/ml. You then have the option of a planned vaginal delivery.

Your baby will need to take AZT syrup for four to six weeks after he/she is born.

If you are in good health at the beginning of your pregnancy, but become ill because of HIV later in your pregnancy and have to start taking HAART during your pregnancy, then the aim should be to get your viral load undetectable. You should continue to take HAART after your baby has been delivered.

Your baby will need to take AZT syrup for four to six weeks after he/she is born.

High viral load?
If HIV has caused serious damage to your immune system, or if you have a high viral load, then you are advised to take HAART, including two drugs from the nucleoside analogue class (NRTIs), ideally AZT and 3TC, and either the non-nucleoside analogue (NNRTI) nevirapine or a protease inhibitor. The higher your viral load, the earlier during your pregnancy you will need to start taking treatment. If you still have a detectable viral load before giving birth, then you need to have a caesarean delivery, but if your viral load is below 50 copies/ml you could have a planned vaginal birth.

Your baby will need to take four to six weeks of AZT syrup.

Already on treatment?
If you become pregnant whilst taking HAART which is successfully suppressing your viral load, you are recommended to continue taking this treatment. You will need to have a special scan between weeks 18 - 20 of your pregnancy called an anomaly scan to see if your baby is developing with abnormalities.

Your baby will need to take four to six weeks of AZT syrup.

If you become pregnant whilst taking HAART and your anti-HIV drugs are not suppressing your viral load to undetectable, then you should have a resistance test to determine your best drug options and then change to these anti-HIV drugs. The aim should be to get your viral load undetectable by the time you deliver. You will need to have an anomaly scan between weeks 18 - 20.

Your baby will need to take four to six weeks of AZT syrup after he/she is born.

Diagnosed late in pregnancy?
If you are diagnosed with HIV very late during pregnancy (32 weeks or later), then you will need to start taking HAART immediately. This will normally include AZT, 3TC and nevirapine. These drugs are able to rapidly pass over the placenta into your baby.

Your baby will need to take four to six weeks of AZT syrup.

Diagnosed during delivery or afterwards?
If you are diagnosed HIV-positive during delivery, or just after, then you should be given a dose of AZT by injection and oral doses of 3TC and nevirapine. Your baby will also need to take a triple combination of anti-HIV drugs for four to six weeks.

Safety of treatment to prevent mother-to-baby transmission
There's some evidence that there is a slightly increased risk of having a premature, or low birth-weight baby if the mother takes anti-HIV drugs during pregnancy, particularly if the mother takes a protease inhibitor. However this is a controversial issue and other evidence suggests that taking anti-HIV drugs does not cause premature delivery.

Preventing mother-to-baby transmission – delivery
The risk of your baby contracting HIV is reduced if you have a planned caesarean (surgical) delivery. This is called an 'elective caesarean' and is scheduled to take place from the 38th week of pregnancy, but will be performed sooner if your labour begins early. Taking anti-HIV drugs during caesarean delivery reduces the risk of you passing on HIV to your baby to very low levels. However, as with all surgery, caesarean delivery carries some risk, which should be fully discussed before you agree - give consent - to the procedure.

You are strongly recommended to have a caesarean if you have a detectable viral load, or if the only anti-HIV drug you took during pregnancy was AZT.

If your viral load has been consistently undetectable (below 50 copies/ml) then you should be able to have an actively managed vaginal birth. This means that your doctors and midwife will make sure that your labour doesn't last too long and can take other steps to reduce the risk of passing on HIV to your baby.

Preventing mother-to-baby transmission – breastfeeding
Breastfeeding your baby carries a risk of passing on HIV to your baby. This risk might be as high as one in eight, depending on your own state of health, how long breastfeeding continues, and whether the baby receives any food or water in addition to breast milk. In the UK and other countries where safe alternatives to breastfeeding are available, you are strongly recommended to feed your baby with formula feed from birth. Detailed advice and support on how to do this is available from medical services and you should ask for help if you have difficulties meeting the cost.