Preventing mother-to-baby transmission with anti-HIV drugs

Taking anti-HIV drugs can dramatically reduce the risk of you passing on HIV to your baby.

There are two different ways in which these drugs act.

First, they reduce your viral load so your baby is exposed to less HIV while in the womb and during birth. The aim of HIV treatment is to get, and keep, your viral load to undetectable levels (below 40 or 50 depending on the sensitivity of the test your clinic uses).

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

Two drugs have been shown to be very effective at preventing mother-to-baby transmission of HIV in the second of these ways. These are the nucleoside analogue (NRTI) AZT (zidovudine, Retrovir) and the non-nucleoside (NNRTI) nevirapine (Viramune). It’s also likely that other drugs are also very effective, but these haven’t been tested as extensively.

The ways in which anti-HIV drugs are used (on their own or in combination with other anti-HIV drugs) will depend on the damage HIV has done to your immune system, and the point in your pregnancy when your HIV was diagnosed.

In the UK, and other countries where it is easy to access anti-HIV drugs, 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 would limit your ability to benefit from nevirapine or related drugs in the future, when you may need them to protect your own health. Nor should nevirapine be used in combination with other HIV drugs if you have a CD4 cell count above 250, as there is a risk of potentially dangerous side-effects.

If you have a CD4 cell count that is high enough to protect you from becoming ill because of HIV, and a low HIV viral load, and you are not ill because of HIV, then UK doctors recommend that you should receive treatment with AZT (zidovudine, Retrovir) during the final three months (third trimester) of pregnancy. You will also be given an intravenous dose of AZT during labour, and will need to have a caesarean rather than a vaginal delivery.

Another option is to take a short course of three anti-HIV drugs during the last few months of pregnancy in order to get your viral load undetectable. You will then have the option of having a planned vaginal delivery.

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

If HIV has damaged your immune system, meaning that you are vulnerable to infections, or if you have a high viral load, then you are advised to take three anti-HIV drugs, including the NRTIs AZT (zidovudine, Retrovir) and 3TC (lamivudine, Epivir), and the NNRTI nevirapine or a ritonavir-boosted protease inhibitor. You should not take nevirapine if your CD4 cell count is above 250. The higher your viral load, the earlier in pregnancy you will need to start taking treatment. If your viral load is still detectable before delivery, then you will need to have a caesarean delivery. However, an undetectable viral load should mean that you have the option of a planned vaginal delivery.

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

If you become pregnant whilst taking anti-HIV drugs that are successfully suppressing your viral load, you are recommended to continue taking them. You will need to have a special scan at week 20 of your pregnancy, called an anomaly scan, to see if your baby is developing with abnormalities, but it's good to know that the risk of this is very low.

Efavirenz (Sustiva) is not recommended for use during pregnancy because animal and laboratory studies suggested that it could increase the risk of birth defects. If you become pregnant whilst taking efavirenz you should contact your HIV clinic to discuss your treatment options.

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

If you are diagnosed with HIV very late during pregnancy (week 32 or later), you will need to start taking a combination of three anti-HIV drugs immediately. These should be AZT (zidovudine, Retrovir), 3TC (lamivudine, Epivir) and nevirapine (Viramune) . However, if  your CD4 cell count is above 250 nevirapine should be replaced with a ritonavir-boosted protease inhibitor; this is because the women starting nevirapine with a CD4 cell count of 250 or above have an increased risk of liver side-effects . These drugs are able to rapidly pass across the placenta into your baby.

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

If you find out you have HIV during delivery, or just after, then you should be given a dose of AZT (zidovudine, Retrovir) by injection and oral doses of AZT and nevirapine (Viramune). Your baby will also need to take a triple combination of anti-HIV drugs.