AZT (zidovudine, Retrovir) is the only anti-HIV drug that is fully approved for use during pregnancy.

Current guidelines from the British HIV Association recommend that pregnant women take the anti-HIV drugs they require regardless of their pregnancy, with the exception of efavirenz (Sustiva)^[1]. However, women who would otherwise not require anti-HIV therapy due to high CD4 cell counts and low viral loads, can reduce the chance of mother-to-baby transmission by taking AZT during pregnancy and labour^[2][3][4]. Current guidelines recommend AZT monotherapy in women with HIV viral loads below 10,000 copies/ml and wild-type virus who do not require or want to take antiretroviral therapy during pregnancy and are willing to deliver by Caesarean section prior to the onset of labour.

AZT monotherapy should begin in the third trimester of pregnancy, at a dose of 100mg five times per day. During labour, AZT should be administered intravenously at 2mg/kg over one hour, followed by 1mg/kg per hour until the umbilical cord is clamped. The baby should then be given 2mg/kg AZT by mouth every six hours starting within twelve hours of birth, until six weeks of age. For babies that cannot be given the oral solution, AZT should be given intravenously at 1.5mg/kg, infused over 30 minutes, every six hours^[5][6].

There are no serious short-term side-effects of AZT monotherapy for the mother or the child, and studies have found no long-term effects of AZT treatment before or during birth on birth defects, growth, development or risk of tumours in uninfected babies^{[7][8][9][10][11]}. Preliminary findings also suggest there is no difference in the risk of disease progression between women who take AZT and who take a placebo, after 18 months follow-up^[12]. However, there is some evidence that babies who do become infected after AZT exposure may have worse outcomes than HIV-positive babies who do not receive AZT before or during birth^[13][14]. Further studies following mothers and babies are underway.

Although breast-feeding by HIV-positive women is not recommended, mothers given AZT during birth also tend to have lower viral loads in their breastmilk, thereby further reducing the chances of transmission to breastfed infants. However, when women stop taking AZT, there is a burst in viral load, which may increase infant exposure to the virus^[15]. For more information, see Breastfeeding.

The addition of nevirapine (Viramune) to short-course AZT for the mother or baby may further reduce the chance of mother-to-child transmission of HIV. For further information on the use of antiretroviral drugs to prevent mother-to-child transmission of HIV, see Antiretroviral treatment during pregnancy.