Mother-to-child transmission of HIV can occur during gestation ( in utero transmission) or during delivery when the newborn comes into contact with maternal blood and cervical-vaginal secretions. In the absence of any intervention, it is estimated that 25.0% of pregnant women who are HIV positive will transmit the virus to their infant either during pregnancy or at birth. If a seropositive mother breastfeeds her baby, the risk of transmission increases to an estimated 35.0%.Footnote 1
In 2008, it was estimated that 15.7 million women worldwide were living with HIV.Footnote 2 For this same year, approximately 1.4 million HIV-positive women gave birth to a child; 91.0% of these births occurred in sub-Saharan Africa.Footnote 3
This Epi Update presents a profile of perinatal HIV transmission in Canada and discusses existing screening approaches for pregnant women in the provinces and territories.
The data presented in this section are derived from several provincial government sources. However, the majority of surveillance data were provided by the Canadian Pediatric AIDS Research Group (CPARG), a body that collects national data on the HIV status of newborns perinatally exposed to HIV. Support for the development of the Canadian Perinatal HIV Database has been provided by the Canadian HIV Trials Network and the Surveillance and Risk Assessment Division of the Public Health Agency of Canada (PHAC). Data on infants born to women known to be HIV positive during pregnancy are accessible in the annual publication HIV and AIDS in Canada, Surveillance Report to December 31, 2008.
The figures presented here relate to all newborns known to have been perinatally exposed to HIV in Canada. However, not all women know their HIV status, which means that not all HIV-positive pregnant women in Canada are included in the data; therefore, it would not be valid to calculate vertical transmission rates from the data.
Between 1985 and December 31, 2008, a total of 67,442 positive HIV tests were reported to PHAC. Of the 61,949 adult cases for which information on sex was available, 10,799 or 17.4%, were women. Of the positive HIV tests reported among adult women, 74.5% involved women who were 15 to 39 years of age.Footnote 4
In the early 1990s, according to CPARG, between 50 and 80 newborns in Canada were known to have been perinatally exposed to HIV each year. In 2008 that figure had risen to 238 per year. Of the 2,851 newborns known to have been exposed to HIV between 1984 and 2008, 523 confirmed cases of infection and 2,291 cases confirmed not to be infected were reported. The infection status of the remaining 37 newborns has not been confirmed (and may include some infants who have been lost to follow-up). Of the 93 infants confirmed to be HIV infected since 2000, none died of AIDS-related causes, 11 died of causes other than AIDS, and 1 was lost to follow-up.Footnote 4
Available data indicate that the rate of mother-to-child transmission in high-income countries has improved significantly since the introduction of antiretroviral therapies. In 2008 it was estimated that, since 2002, fewer than 250 infants had been born with HIV infection each year in the United States, representing a perinatal rate of less than 2.0%.Footnote 5 In 1991, by contrast, the Centers for Disease Control and Prevention estimated that 1,650 infants had acquired HIV perinatally.Footnote 6 In England in 2007, the rate of mother-to-child transmission was 2.0%, a significant decrease compared with the 12.0% national rate observed in 1999.Footnote 7
Overall, the situation of infants perinatally exposed to HIV has greatly improved during the past decade. As the number of persons living with HIV in Canada has increased, so too has the number of infants perinatally exposed to HIV. However, the number of these infants who are subsequently confirmed to be infected has declined dramatically in recent years, both as a percentage and in absolute numbers. In 2001, for example, a total of 168 infants were perinatally exposed to HIV. Out of these, 17 (10.1%) were confirmed to be infected. In 2008, by contrast, 4 out of a total of 238 exposed infants (1.7%) were confirmed as infected. The more widespread administration of effective antiretroviral therapies (ART) has played a large role in this outcome: in 2008, 87.8% of HIV-positive pregnant women had benefited from these therapies. The average percentage of infants who were perinatally infected during the 1984-2000 period (33.9%) was approximately 6 times greater than the average percentage infected between 2001 and 2008 (5.2%).Footnote 4
Between 1984 and 2008, 80.4% of the 2,851 infants known to have been perinatally exposed to HIV were confirmed not infected. Since the World Health Organization first issued recommendations for the use of ARV drugs to prevent mother-to-child transmission in 2000, both the number and proportion of HIV-positive pregnant women receiving ART in Canada has increased (Figure 1). In 2000, 77.9% of known HIV-positive pregnant women were receiving any ART. By 2008, the rate was 87.8%. Moreover, between 1984 and 2008, the proportion of HIV-positive pregnant women who received ART during the perinatal period and whose infants were confirmed to be infected (1.6%) was significantly lower than of those who did not receive ART (47.9%).Footnote 4
Between 1984 and 2008, 2,851 births were reported in which an infant was perinatally exposed to HIV; 97.5% of these cases included information on ethnicity/race.Footnote 4
Each province and territory determines which approach it will use to screen pregnant women for HIV (Table 1). The two systems currently in use are voluntary screening (opt-in) or routine screening with right of refusal (opt-out). The Canadian Medical Association recommends voluntary screening since a positive result can have an impact on many different aspects of a person's life.Footnote 8 However, routine screening with right of refusal reaches a larger proportion of pregnant women.
|Province/territory||Testing approachTable 1 - Footnote *||Year|
|Northwest Territories||Opt-out||1993, revised in 1998|
|Saskatchewan||Opt-out||1999, revised in 2004-2005|
|Manitoba||Opt-out||2002, revised in 2006|
|New Brunswick||Opt-out||1999, revised in 2005|
|Prince Edward Island||Opt-in||1999|
|Newfoundland and Labrador||Opt-out||1992, revised in 1994|
According to prevalence studies among pregnant women in several provinces, the HIV prevalence rates between 1998 and 2008 in this group ranged from 2 to 9 per 10,000, but rates are not available for all provinces and territories. Table 2 presents the percentage of pregnant women screened for HIV virus in several provinces.
|Province/territory||Percentage of pregnant women screened for HIV|
|British Columbia||83.4% in 2003Footnote 9|
|Alberta||97.0% in 2006Footnote 10|
|Ontario||97.6% in 2009Footnote 11|
Despite significant progress made in ART to prevent perinatal HIV transmission, research efforts to improve these therapies and treatment adherence continue. Research efforts prevent perinatal HIV transmission, as well as study factors that contribute to treatment adherence.
Geographic origin, poverty, and social marginalization are some of the major factors influencing one's risk of contracting a communicable disease. The increased immigration to Canada from HIV-endemic regions of the world contributes to Canada's growing number of people living with HIV/AIDS, including pregnant women, children and infants.
Between 1984 and 2008, 205 infants confirmed to be infected with HIV were born in Ontario. Of this- number, 133 (68.6%) were born to mothers from countries where HIV is endemic.Footnote 19
The rising number of HIV cases among Aboriginals also translates into rising numbers of Aboriginal women of reproductive age who are living with HIV.
Blood specimens were taken from 5,232 pregnant Aboriginal women in British Columbia during the years 2000 to 2003.Footnote 18 Testing of these samples revealed an HIV prevalence rate among these women that was 7 times higher than the estimated rate of the general population during that same time period.
Although there has been a decline in the rate of mother- to-child transmission of HIV, the absolute number of infants exposed to HIV in-utero or during birth is on the rise. It is thus important that all pregnant women, as well as women considering pregnancy, continue to have access to prenatal care that includes the offer of HIV testing, HAART, and appropriate counselling and care.
For more information, please contact:
Surveillance and Risk Assessment Division
Centre for Communicable Diseases and Infection Control
Public Health Agency of Canada
Postal locator: 0602B
Ottawa, ON K1A 0K9
Tel: (613) 954-5169
Fax: (613) 957-2842
To promote and protect the health of Canadians through leadership, partnership, innovation and action in public health.
Public Health Agency of Canada