Maternal HIV infection during pregnancy or breastfeeding poses substantial transmission risk for infants

There is a high risk of mother-to-child HIV transmission if a woman acquires HIV after delivery and then breastfeeds, a Chinese study published in the September 1^st edition of the Journal of Infectious Diseases reports.

A total of 104 women who contracted HIV through blood transfusions post-delivery were included in the study. All the women breastfed and 36% of their infants were infected with HIV. This is much higher transmission rate than that seen in women whose HIV is diagnosed early in pregnancy.

“This report…highlights the broader problem of acute HIV infection during pregnancy and breast-feeding”, comment the authors of an accompanying editorial.

In 2007 an estimated 320,000 children were newly infected with HIV as a consequence of mother-to-child transmission. Many of these infections were due to breastfeeding. This mode of HIV transmission has been extensively studied in populations of women who had chronic HIV infection, but less is known about the risk of transmission when a mother acquired HIV either late in pregnancy or after delivery.

Investigators from China therefore designed a retrospective study including 104 women in Hubei and Hebei who became infected with HIV as a result of blood transfusions. These transfusions were provided after delivery because of either excessive blood loss during delivery, or blood loss during surgery for a caesarean delivery.

These women had 106 infants, 38 of whom were infected with HIV because of breastfeeding.

The infants were breastfed for an average of 17 months. Breast disease (mastitis or cracked nipples) was reported by 16 women, and ten of their infants were infected with HIV. A much smaller proportion of the infants of mothers who did not report breast disease acquired HIV (28 of 90).

Overall, the transmission rate was 31% for mothers with no history of breast disease, but 63% when mastitis or cracked nipples were reported.

These rates of transmission were much higher than the 9% rate seen when a woman with chronic HIV breastfeeds. The investigators suggest that this is because the women infected post-delivery were especially infectious during breastfeeding, as early (or acute) HIV infection is associated with a high viral load.

HIV caused the deaths of 16 of the mothers (15%) and five of the children (13%). None of the children died before the age of five, and the mean duration of HIV infection for both the mothers and their children before the initiation of antiretroviral therapy was twelve years.

Mortality rates for infants infected with HIV by their mothers are normally between 35% and 59% by two years of age. The investigators believe that both the low mortality rate and long-term survival of the infants in their cohort “suggests even a brief window of HIV free life enables the immune system to stave off rapid disease progression in most cases", however they caution, "such a profound conclusion warrants follow-up studies.”

The authors of the accompanying editorial state that the study has implications for programmes to prevent mother-to-child transmission. They recommend that woman who test HIV-negative early in pregnancy should have repeat tests later in pregnancy, during delivery, and at child healthcare visits.

They conclude, “the study…highlights the importance of identifying new peripartum maternal HIV infections in unfortunate instances where a negative antenatal test result is not the final word.”