Since effective strategies have been introduced to reduce the likelihood of mother-to-child transmission (MTCT) of HIV, rates in the UK and Ireland have remained below 2% for nearly ten years due to routine antenatal testing and potent drug regimens, a UK team of researchers report in the May 11th issue of the journal AIDS.
Clinical studies have found that various antiretroviral drug regimens taken during pregnancy in combination with the type of delivery, plus avoidance of breastfeeding can reduce mother-to-child transmission. Different strategies are recommended depending on the status of the mother's HIV infection.
The standard of care in many resource-rich countries is highly active antiretroviral therapy for the mother but British guidelines also include the option of AZT monotherapy plus Caesarean section at delivery for women with high CD4 cell counts and pretreatment viral load of less than 6,000–10,000 copies/ml.
“A more tolerant approach to mode of delivery for women who achieve full viral suppression on HAART has become evident, with rates of planned vaginal delivery rising,” the authors note.
UK and Ireland MTCT rates fell from about 20% in 1993 to 2% in 1998. Since then, routine antenatal HIV testing means that most HIV-infected pregnant women are diagnosed before delivery. Since few studies have assessed the effectiveness of different combinations of drugs and delivery modes at a population level, Claire Townsend (University College London, UK) and colleagues analysed data routinely reported by obstetricians and paediatricians to a comprehensive national surveillance scheme. Multiple births were excluded from the analysis. Information was analysed from all infants whose infection status had been reported.
Between 2000 and 2006, 5930 infants were born to HIV-positive mothers: most mother were black Africans, on potent anti-HIV therapy (three or more drugs), and had a planned Caesarean section. About 45% of mothers were diagnosed before pregnancy. Overall, the MTCT rate was 1.2% (61/5151) and 0.8% (40/4864) for women who had received at least 14 days of antiretroviral therapy (p=0.15). Rates of MTCT fell during the survey period despite an increase in the absolute numbers of births.
Transmission rates following combinations recommended in British guidelines were 0.7% for potent anti-HIV treatment with planned Caesarean section, 0.7% for potent anti-HIV therapy with planned vaginal delivery, and 0% for AZT monotherapy with planned Caesarean section. Receiving no drug therapy was the strongest risk factor for transmission, while unplanned vaginal delivery carried a significant increased risk compared with planned vaginal delivery or planned Caesarean section. Longer duration of potent anti-HIV treatment was significantly linked with reduced risk of transmission (p= 0.007), and very few infants were HIV-infected if their mothers had viral loads
These low rates are “a remarkable achievement,” the authors write. Early testing of pregnant women remains a priority and further reductions in MTCT may be seen with better uptake of testing in pregnancy. Current options offered to HIV-positive pregnant women in British guidelines appear to be effective, they conclude.
Reference
Townsend C et al. Low rates of mother-to-child transmission of HIV following effective pregnancy interventions in the United Kingdom and Ireland, 2000–2006. AIDS 22: 973–981, 2008.