Factors responsible for mother-to-child HIV transmission in Ontario, Canada, 1996–2008

OBJECTIVE: Despite a high uptake of HIV screening and anti-retroviral prophylaxis in Ontario, several cases of mother-to-child (MTC) transmission occur every year. We wished to examine the modifiable factors responsible for MTC HIV transmission in Ontario, in particular HIV testing, antiretroviral prophylaxis and breast-feeding.METHODS: Using the Ontario data from the Canadian Perinatal HIV Surveillance Program, we examined potential correlates of late maternal HIV diagnosis (i.e., diagnosed at or after delivery) among women delivering from 1996 to 2008. To better understand the factors responsible for MTC HIV transmission, we reviewed the medical charts of 35 HIV-infected infants born in Ontario.RESULTS: Among the 645 HIV-infected mothers, 85 (13.2%) had late HIV diagnosis. The proportion with late HIV diagnosis significantly decreased during the study period, but did not differ by race/ethnicity group or maternal exposure category. With respect to the mothers of the 35 HIV-infected infants, 27 (77%) were diagnosed with HIV at or after delivery. The reasons no prenatal HIV test was performed were: not offered, offered but refused, no prenatal care, denied HIV testing history, and offered but not done. Reasons for no or incomplete antiretroviral prophylaxis (ARP) among eight mothers diagnosed prior to or during pregnancy were: refused or non-compliant with ARP, and failed to inform care provider of HIV status.CONCLUSIONS: Despite the recommendation for universal prenatal HIV counseling and voluntary testing adopted in Ontario, MTC transmission continued to occur, mostly due to late HIV diagnosis of the mother. Future work to reduce perinatal HIV infection should focus on enhancing timely HIV testing of pregnant women.