Earlier Initiation of ART and Further Decline in Mother-to-child HIV Transmission Rates, 2000-2011

Objectives: To analyze mother-to-child HIV transmission (MTCT) rates over time in light of changes in management, demographic, and pregnancy characteristics.

Design: Population-based surveillance data on diagnosed HIV-positive women and their infants are routinely collected in the UK and Ireland.

Methods: A total of 12486 singleton pregnancies delivered in 2000-2011 were analyzed. HIV infection status was available for 11515 infants (92.2%).

Results: The rate of MTCT declined from 2.1% (17/816) in 2000-2001 to 0.46% (nine of 1975, 95% confidence interval: 0.21-0.86%) in 2010-2011 (trend, P=0.01), because of a combination of factors including earlier initiation of antenatal combination antiretroviral therapy (cART). Excluding 63 infants who were breastfed or acquired HIV postnatally, MTCT risk was significantly higher for all modes of delivery in women with viral load of 50-399  copies/ml (1.0%, 14/1349), compared with viral load of less than 50 copies/ml (0.09%, six of 6347, P<0.001). Among the former (viral load 50-399 copies/ml), the risk of MTCT was 0.26% (two of 777) following elective cesarean section and 1.1% (two of 188) following planned vaginal delivery (P=0.17), excluding in-utero transmissions. MTCT probability declined rapidly with each additional week of treatment initially, followed by a slower decline up to about 15 weeks of cART, with substantial differences by baseline viral load.

Conclusion: MTCT rates in the UK and Ireland have continued to decline since 2006, reaching an all-time low of 5 per 1000 in 2010-2011. This was primarily because of a reduction in transmissions associated with late initiation or nonreceipt of antenatal cART, and an increase in the proportion of women on cART at conception.