Perinatal Transmission of HIV

HIV/AIDS Epi Updates

April 2003

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Perinatal Transmission of HIV

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Introduction

Perinatal (or vertical) transmission of HIV is the transmission of HIV from an infected pregnant woman to her newborn child. Transmission can occur during gestation (in utero), during delivery (when the fetus makes contact with maternal blood and mucosa in the birth canal) or after delivery, through breastmilk. Therefore, women of childbearing age (15-44 years) are of particular concern since they may transmit HIV infection to their newborn children. In this report, the status of perinatal HIV transmission in Canada and HIV testing recommendations for pregnant women are discussed.

AIDS Case Reports

As of June 30, 2002, 18,124 AIDS cases among adults have been reported to the Centre for Infectious Disease Prevention and Control (CIDPC) in Canada, including 1,437 (7.9%) among women (aged 15 and older). Of these, 1,152 (80%) were among women of childbearing age (15-44 years).¹ For pediatric AIDS cases (children 0-14 years), 208 cases have been reported, and 165 of these (79%) were attributed to perinatal transmission.²

HIV among Pregnant Women and Women of Childbearing Age

HIV prevalence studies among pregnant women indicate a provincial rate for Canada of about 3-4/10,000, although data for some provinces have not been updated for 5 or more years. The provincial range is from 1.9/10,000 (Ontario 1991-1992³) to 8.7/10,000 (Newfoundland 1991-1993⁴) and large metropolitan areas have higher rates (4.7 for Vancouver versus 3.4 for the rest of B.C. in 1994⁵, and 15.3 for Montreal versus 5.2 for the province of Quebec in 1990⁶). However, even provinces without large metropolitan areas have significant rates (for example, 4.1/10,000 in New Brunswick for 1994-1996⁷) and data from Manitoba suggest an increasing trend of HIV infection among women of childbearing age (from 0.7/10,000 in 1991 to 3.2/10, 000 in 1994-1995⁸). A study is currently underway in Ontario to update the HIV prevalence in pregnant women. Preliminary results indicate a prevalence of 3.7/10,000 among the approximately 72% of pregnant women who agreed to voluntary testing in the third quarter of 2002.⁹

Transmission of HIV from Mother to Child

In Ontario, 34 HIV-infected infants were born to HIV-positive mothers during 1984-1989, and 59 such infants were born during 1990-1997. During 1984-1997, just over 58% of the HIV positive mothers reported their risk factor for HIV as being from an endemic country, where heterosexual transmission of HIV is the most likely mode of transmission.¹⁰

At the national level, over the past decade, the number of infants born to HIV-infected mothers (HIV-exposed infants) has increased from 56 in 1991 to 138 in 2001, as seen in Figure 1.² The figure also depicts the reported number of infants born to HIV positive mothers and the number of infants who, to date, have confirmed HIV infection (data from the Canadian Pediatric AIDS Research Group).²

Of the reported 1,384 infants who were exposed to HIV from their mothers between 1984 and 2001, 375 have been confirmed HIV positive and an additional 56 have indeterminate serostatus and are currently being monitored. Of the exposed infants over the past decade, an increasing proportion had received some treatment during the course of their gestation and/or after birth. This is in part reflected in the decreasing number of HIV positive infants born since 1996.

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Provincial Prenatal HIV Screening Recommendations

In all Canadian provinces, HIV testing of pregnant women remains the choice of the woman. There are two different prenatal HIV testing approaches in Canada. Under the opt-in approach, women typically are provided pre-HIV test counselling and must consent specifically to an HIV test. Under the opt-out approach, women are notified that an HIV test will be included in the routine prenatal tests and procedures and that they may refuse testing. Guidelines and/or recommendations have been developed in each province to encourage informed decisions in terms of HIV testing during pregnancy.

Newfoundland and Labrador: In 1997, the Newfoundland and Labrador Advisory Committee on Infectious Diseases recommended that HIV testing be added to the existing prenatal screening program. HIV testing is done as part of the routine prenatal screen, unless the woman declines. The Newfoundland and Labrador Medical Association and the provincial Public Health Laboratory and Department of Health and Community Services have supported this recommendation and have worked to actively notify physicians and patients of this recommendation.¹¹

Prince Edward Island: In June 1999, the PEI Department of Health and Social Services formally adopted a policy of supporting HIV testing for all pregnant women and recommends that physicians offer HIV testing at the first prenatal visit.¹²

Nova Scotia: The Reproductive Care Program recommends that HIV testing should be offered to all pregnant women, together with other prenatal tests in the first trimester. Women who decline testing in the first trimester or who are known to engage in high risk activities should be offered testing again during the latter stages of their pregnancy.¹²

New Brunswick: The New Brunswick Medical Society's Subcommittee on Perinatal Health Care recommended, in July 1999, that physicians should routinely encourage all pregnant women to be tested for HIV with appropriate pre- and post-test counselling and informed consent. In addition, nominal and non-nominal HIV testing and counselling are available through physicians at Public Health sexual health centres and provincial correctional institutions, and anonymous testing is available at Public Health sexual health centres and correctional institutions in the province.¹³

Quebec: Since 1997, as part of an intervention program on HIV infection and pregnancy, the Ministry of Health and Social Services, in accordance with the College of Physicians, initiated a program recommending that all pregnant women and women contemplating pregnancy be offered an HIV test. This program is currently under revision in view of the evaluation data available. A new policy for HIV testing among pregnant women will be implemented in 2003.¹⁴  

Ontario: On December 1, 1998, the Minister of Health announced that the prenatal screening program would be expanded to include HIV testing. Through this expanded program, all pregnant women are offered an HIV test as part of their prenatal care. The HIV test is performed only after counselling is provided and informed consent is given.¹⁵

Manitoba: On April 24, 2002, Dr. Greg Hammond, Director, Public Health Branch, Manitoba Health sent out a province-wide letter announcing the revised prenatal HIV testing policy. The current policy strongly recommends that all health care providers provide appropriate information and offer HIV testing to all pregnant women as part of routine prenatal care.  The decision not to be tested should be voluntary and based on informed choice.¹⁶

Saskatchewan: The College of Physicians issued guidelines for physicians to assess a woman's risk and inform her that testing is available.¹⁷

Alberta: On September 1, 1998, HIV screening was added to the routine prenatal blood tests for all women in Alberta. HIV screening is done unless the woman declines to be tested (opt-out policy). As of August 2002, initial screening and confirmatory testing for HIV and hepatitis B on prenatal blood samples is conducted at the Provincial Laboratory for Public Health (Microbiology). The Canadian Blood Services laboratories in Calgary and Edmonton continue to do blood grouping, Rh determination, anti-erythrocyte antibodies.¹⁸

British Columbia: In June 1994, the B.C. Ministry of Health recommended that HIV testing be offered as a routine prenatal component, with informed consent and pre- and post-test counselling.¹⁹

Northwest Territories (NWT): In 1993, the Northwest Territories Maternal and Perinatal Committee, which has representation from the Department of Health and Social Services and the Northwest Territories Medical Association, recommended that all pregnant women be routinely tested for HIV. Prenatal HIV testing was initially introduced as an opt-in program, but in1998 it became fully integrated with routine prenatal care, although women are still provided the opportunity to opt out.²⁰

Nunavut (new territory separated from the NWT in 1999): same policy as in NWT.²¹

Yukon: In 1994, the Chief Medical Officer of Health, in conjunction with Yukon Communicable Disease Control, "strongly recommended" testing of all pregnant women. Women who present for testing are also encouraged to recommend their partner be tested as well.²²

Canadian Women Can Access Prenatal HIV Screening Programs

Data from prenatal HIV screening programs can provide important information on the effectiveness of prenatal HIV screening recommendations. Below are data from several provinces:

Alberta: During the first year of their program, 4% of a total of 51,500 eligible pregnancies declined testing. These data have found 15 HIV positive women, for a rate of 2.91/10,000. In the following year, 2.4% of pregnant women declined testing and the HIV prevalence rate was 3.47/10,000.¹⁸

Quebec: A recent study examined changes in medical practice regarding prenatal HIV testing in Ste-Justine hospital, the referral centre for the province of Quebec, after the 1997 implementation of the HIV-screening strategy during pregnancy. The program consists of universal counselling and offering HIV testing to all pregnant women. The study found that the percentage of HIV tests offered to pregnant women was 61.8% in 2001. The percentage of tests offered in the previous years was fairly constant at 60.6% in 1998 and 57.4% in 1999 and 2000.²³

British Columbia: About 55% of pregnant women were tested for HIV in 1995; this proportion was estimated to be up to 80% in 1999 (60% through routine prenatal testing and 20% through groups identified as high risk).²⁴

Ontario: HIV-testing uptake has gradually increased form 40% in 1999 to 79% in the third quarter of 2002, 72% during the pregnancy and 6% previously. The highest HIV test uptake was in Windsor-Essex (94%) and the lowest in Kent-Chatham (61%). In only three health units, test uptake was less than 70%. Among the 318,386 pregnancies for which the woman was tested for HIV, 119 were HIV?positive giving a rate of 3.7 per 10,000. ⁹

Newfoundland and Labrador: Almost all pregnancies in 2000 (estimated to be 9,000) were tested for HIV and no HIV-positive results were found.²⁵

Antiretroviral Treatment Can Reduce the Likelihood of Transmission of HIV from Mother to Infant During Pregnancy

HIV testing during pregnancy can provide the opportunity to offer antiretroviral treatment to the mother and infant. For example, a full AZT protocol, which includes administering AZT to the mother during the second or third trimester, during labor and delivery, and after delivery to the infant for 6 weeks can reduce the likelihood of transmission of HIV from mother to newborn by about 2/3.²⁶ Clinical trials in developing countries have recently shown that short course AZT regimes (given to pregnant women starting at 36 weeks gestation and during labor) can reduce vertical transmission rates by about 50%.²⁷ Recent studies indicate that even greater reductions can be achieved using single-dose nevirapine.²⁸

In Quebec, at Sainte-Justine Pediatric Hospital, the use of antiretroviral therapy (AZT) reduced the likelihood of mother-to-infant HIV transmission from 28.3% transmission among mother-infant pairs who had not received any AZT, to 3.75% for mother-infant pairs who had received partial or full AZT therapy.²⁹

Similarly, a more recent study (1993-1999) on AZT use in B.C. found a reduction in the HIV vertical transmission rate from 28% in untreated women-infant pairs to 13% in partially-treated pairs and 0% in completely-treated pairs.³⁰

In Alberta, a study examining the prevention of perinatal HIV transmission from 1998 -1999 found that when HIV-positive mothers were treated with antiretrovirals during pregnancy and intrapartum, 31 of 36 babies (86%) were not HIV infected.³¹

Data from the national surveillance program of Pediatric Centres and HIV clinics in Canada (where 95% of the diagnosed HIV-exposed infants are followed) indicate that the proportion of pregnant women receiving antiretroviral therapy has increased steadily in the last 5 years, from 37% in 1994 to 53-58% in 1995-1996, 72% in 1997 and 84% in 1998. The resulting perinatal HIV transmission rate was reduced to 4.8% with AZT monotherapy and to 2.5% with combined therapy.³² Recent data from this group indicate that from 1995 - 1999, of the 93 HIV infected infants born during this period, 83 were born to women who did not receive antiretroviral therapy. Most of these women were not offered antiretroviral therapy because their HIV status was not identified before or during their pregnancy.³³

Canadian Prenatal HIV Screening Programs Are Valuable

Screening pregnant women for HIV clearly represents an important opportunity to prevent the transmission of HIV to infants. From the perspective of a cost-benefit analysis (which includes the costs of screening tests, counselling and treatment), the benefit of screening is obviously greater in areas with higher HIV prevalence among childbearing women. For areas of lower HIV prevalence, the benefit per unit cost is more dependent on variables such as whether or not physicians bill separately for the counselling time associated with prenatal HIV testing.³⁴ It is estimated that if such programs screened 90% of pregnant women across Canada, there would be a 65% reduction in the number of HIV-infected newborns (compared to no prenatal testing and assuming 24% of untreated pregnancies and 6% of treated pregnancies result in HIV-infected infants).³⁵ Assuming HIV prevalence rates of 6/10,000 among pregnant women in B.C. Ontario and Quebec and 3/10,000 elsewhere, this reduction in absolute number terms would be from 56 to 20 infected newborns, or 36 infections prevented annually.

Comment

There is still a risk for the perinatal transmission of HIV in Canada and as more women are becoming infected, this risk is increasing. Elsewhere, we have estimated that about 15,000 Canadians (including women) are HIV-infected, but unaware of their infection (see Epi Update entitled "Prevalent HIV Infections in Canada: Up to One-Third May Not Be Diagnosed", April 2003). Given this, and the fact that perinatal infections are preventable, it is important that all pregnant women, and women considering pregnancy, should have access to prenatal care that includes the offer of HIV testing as well as appropriate counselling and care.

References

1. Health Canada. HIV and AIDS in Canada: Surveillance Report to June 30, 2002. Division of HIV/AIDS Epidemiology and Surveillance, Centre for Infectious Disease Prevention and Control, Public Health Agency of Canada, November 2002.

2. Health Canada. HIV and AIDS in Canada: Surveillance Report to December 31, 2001. Division of HIV/AIDS Epidemiology and Surveillance, Centre for Infectious Disease Prevention and Control, Public Health Agency of Canada, April 2002.

3. Coates RA, Frank JW, Jackson L et al. The Ontario HIV seroprevalence study of childbearing women. Can J Infect Dis 1992;3:16A-17A.

4. Ratnam S, Hogan K, Hankins C. Prevalence of HIV infectionamong pregnant women in Newfoundland. Can Med Assoc J1996;154(7):1027-31.

5. Pi D, Ballem PJ, Schechter MT. Final Report: the BC prenatal study: 1989-94. Report submitted to Laboratory Centre for Disease Control, Jan 1995, and Rekart M. HIV in pregnancy. BC AIDS Update Quarterly Report: 4th Quarter 1995.

6. Seroprevalence of HIV-1 antibodies in women giving birth to live infants: a five-year trend analysis for selected regions outside Montreal, 1989-93. Report submitted to Laboratory Centre for Disease Control, Nov 1994 and Hankins D, Laberge C, Lapointe N et al. HIV infection among Quebec women giving birth to live infants. Can Med Assoc 1991;144 (3):277-80.

7. Getty G, Leighton P, Mureika R et al. Seroprevalence of HIV infection in pregnant women in New Brunswick. Can J Infect Dis 1997;8:24A.

8. Blanchard J, Hammond G, Fast M et al. Manitoba antenatal study. Report submitted to Laboratory Centre for Disease Control, June 1996.

9. Remis RS. Unpublished data to be presented at CAHR 2003 conference. April 2003, Halifax.

10. Using HIV Perinatal Surveillance Data for the Evaluation of Prevention Intervention: Provincial example, Ontario. Presentation by Remis R. in the Proceedings of a Scientific Meeting to review the Vertical Transmission of HIV in Canada. Ottawa, Ontario June 11, 1998.

11. Communication with Dr. F. Stratton, Provincial Medical Officer of Health, Department of Health and Community Services, Newfoundland, January 2003.

12. Communication with T. MacDonald, Field Surveillance Officer, Atlantic Region, Health Canada, January 2003.

13. Communication with M. Collette, Epidemiology Program Officer Provincial Epidemiology Service, New Brunswick Department of Health and Wellness, N.B. January 2003.

14. Communication with Dr. D. Auger, Direction de la protection de la santé publique, Ministère de la Santé et des Services sociaux, Quebec. January 2003.

15. Communication with L. Scheidel, Nurse Epidemiologist, Disease Control and Epidemiology Service, Ontario Ministry of Health, March 2002.

16. Communication with M. Wood, Field Surveillance Officer, Cadham Provincial Laboratory, Manitoba Health, January 2003.

17. Communication with S. Harmen, Field Surveillance Officer, Saskatchewan Communicable Disease Control, January 2003.

18. Communication with Dr. G. Jayaraman, Field Surveillance Officer, Alberta Provincial Laboratory for Public Health, January 2003.

19. Communication with E. Wong, Field Surveillance Officer, B.C. Centre for Disease Control, January 2003.

20. Communication with Dr. A. Corriveau, Chief Medical Health Officer, Department of Health & Social Services, GNWT, January 2003.

21. Communication with Dr. G. Osborne, Assistant Chief Medical Officer of Health, Government of Nunavut, March 2002.

22. Communication with C. Hemsley, Communicable Disease Officer, Yukon Territory, January 2003.

23. M Boucher, J Samson, N Lapointe. HIV Screening among pregnant women in the province of Quebec : Success and Failure. Can J Infect Dis 2002;13 (Suppl A): 30A (Abstract 223)

24. Communication with M. Rekart, B.C. Centre for Disease Control, March 2002.

25. Communication with C.O'Keefe, Disease Control and Epidemiology and M. Pond, Program and Policy Development, Department of Health and Community Services, Newfoundland, April 2001.

26. Connor EM, Sperling RS, Gelber R et al. Reduction of maternalinfant transmission of human immunodeficiency virus type 1 with zidovudine treatment. Pediatric AIDS Clinical Trials Group Protocol 076 Study Group. N Engl J Med 1994;331:1173-80.

27. Shaffer N, Chuachoowong R, Mock P et al. Short course zidovudine for perinatal HIV-1 transmission in Bangkok, Thailand: a randomized clinical trial. Lancet 1998;353(9155):773.

28. Marseille E, Kahn JG, Mmiro F et al. Cost effectiveness of singledose nevirapine regimen for mothers and babies to decrease vertical HIV-1 transmission in sub-Saharan Africa. Lancet 1999;354(9181): 803-9.

29. Antiretroviral Therapy in Pregnant Women (CPARG): Access and Outcome (1995-1997) and the Experience of Transmission of HIV in Treated Pregnant Women at Ste. Justine's Clinic, Quebec. Presentation by Lapointe N. in the Proceedings of a Scientific Meeting to Review the Vertical transmission of HIV in Canada June 1998.

30. Forbes JC, Money DM, Remple VP et al. Effect of antiretroviral use on HIV vertical transmission rate and injection drug use on adherence in British Columbia, Canada. Can J Infect Dis 2000;11:46B {Abstract 246P}.

31. Robinson JL, Bonita EL. Prevention of perinatal transmission of HIV infection. CMAJ 2000;163(7):831-832.

32. King SM, Singer J, Forbes J et al. Trends in antiretroviral therapy (ART) in pregnant women in Canada, 1994-98. Can J Infect Dis 2000;11:57B {Abstract 312}.

33. King SM, Forbes J, Lapointe N, Samson L, Embree J, Vaudry W, Read SE, Singer J and The Canadian pediatric AIDS Research Group (CPARG). Perinatal HIV prevention in Canada. Can J Infect Dis 2001;12(Suppl B):73B (Abstract 365P)

34. Nagarajan KV, Sahai V, Pong RW. Screening pregnant women for HIV infection in Ontario: economic and human resources implications. Final report submitted to Bureau of HIV/AIDS, STD, and TB, Health Canada, March 1998.

35. Archibald CP, Farley J, Yan P, Sutherland J, Sutherland D. Estimating the impact of antenatal HIV testing in Canada: a lesson on the difference between efficacy and effectiveness. Can J Infect Dis 1999;10:43B {Abstract C304}.

For more information please contact:

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Health Canada

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