Screening for HIV in pregnancy eliminates vertical transmission

Jul 23 2015

Canada has almost eliminated mother-to-child HIV transmission, known as vertical transmission, in recent years by ensuring that all women have the opportunity to be screened for HIV in pregnancy and that women with the disease receive treatment before giving birth.

In 2014, there was only one recorded transmission of the virus to babies born to women known to be living with HIV.

These findings were presented at the International AIDS Society 2015 conference in Vancouver by researchers from the Canadian Perinatal HIV Surveillance Program (CPHSP), a national group that has been collecting annual surveillance data about children born to women with HIV in Canada since 1990.

"Effectively, Canada has eliminated vertical transmission," said Dr. Jason Brophy, chair of the Canadian Pediatric & Perinatal AIDS Research Group (CPARG) which runs the CPHSP. CPARG has been active for 25 years in advocating for improved prevention of vertical HIV transmission and better care of children with HIV.

"The World Health Organization definition of elimination is less than two per cent transmission and that's where we are right now. But of course, we'd like to get to zero and I know that we can."

Women who receive combination antiretroviral therapy (cART) during pregnancy do not pass HIV on to their baby. Regular cART treatment is almost 100 per cent effective in preventing transmission when given for enough time to suppress the virus in the mother.

In three separate poster presentations about the surveillance program, CPHSP researchers examined the progress Canada has made in treating women with HIV, preventing the disease in infants as well as opportunities to improve care. They determined which populations are at greatest risk and how public health officials are working with those groups.

Since the 1990s, about half of women with HIV delivering babies in Canada were foreign born. Aboriginal women and women who use injection drugs were also at greater risk of having HIV in pregnancy and had consistently lower rates of treatment. Promising new findings in 2014 show that these two groups now have treatment rates comparable to other women.

"The database has allowed us to assess the national burden of HIV infection through vertical transmission throughout the HIV/AIDS epidemic and to identify the populations at greatest risk," said Joel Singer, professor in the School of Population and Public Health at UBC, who is presenting at IAS 2015. "The happy conclusion, at this point, is that vertical transmission in Canada is rare, and groups which were at excess risk are no longer so."

The researchers say this recent success stems largely from public health initiatives to ensure women in these high-risk populations are tested and receive the proper prenatal care. The researchers say the key to reaching the goal of zero transmission between mothers and infants is to engage hard-to-reach populations in health care and allow them to access prenatal care, HIV testing and cART treatment.

BACKGROUND: Poster presentations

The Canadian Perinatal HIV Surveillance Program (CPHSP): Program Description and Trends in Demographics, Treatment and Transmission

Joel Singer, a professor in the School of Population and Public Health at UBC, presented recent data from the program. In 2014, 97 per cent of all mothers received cART before birth. Notably, Aboriginal women and women who use injection drugs now have treatment rates comparable to other women.

Successes and Failures of Vertical HIV Transmission Prevention Efforts in Canada: Evidence from the Canadian Perinatal HIV Surveillance Program (CPHSP)

Ari Bitnun, a physician at SickKids and associate professor at the University of Toronto, examined cases of vertical transmission in Canada and identified missed opportunities for prevention. Of the 44 cases of vertical HIV transmission in Canada since 2005, 91 per cent occurred in women who got no cART or less than four weeks of cART before delivery. All 11 children diagnosed after three months of age were from provinces with opt-out prenatal HIV screening programs. The data strongly suggest that timely access to prenatal care and screening for HIV early in pregnancy, particularly for women from hard-to-reach populations, is essential if we are to eliminate vertical HIV transmission in Canada.

Geographic Origin Trends Among HIV+ Mothers and Children in Canada and Impact on Vertical HIV Transmission Rates

Jason Brophy, a physician at the Children's Hospital of Eastern Ontario (CHEO) and assistant professor at University of Ottawa, presented research showing that since 1990, half of mothers with HIV delivering in Canada are foreign born. In Quebec and Ontario, these women come most often from Haiti and East Africa, respectively. In Western Canada, Aboriginal women are the largest group of mothers with HIV. Over time, African-born women have become the least likely group to transmit infection to their babies.

Source: University of British Columbia