Low CD4 cells in mums means greater risk of illness and death in their HIV-negative babies

HIV-negative infants whose mothers have advanced HIV disease have an increased risk of hospitalisation and death within the first few months of life, a study published in the December 1^st edition of Clinical Infectious Diseases reports. In particular, the investigators found that the uninfected infants of mothers who had a CD4 cell count below 350 cells/mm³ had a risk of death almost three times greater than that of children whose mothers had stronger immune systems. The investigators suggest that their study has identified “an overlooked population of children at high risk for mortality and morbidity.”

Little is known about rates of illness and death amongst the HIV-uninfected infants of HIV-positive mothers. It is thought that HIV exposure, even if it does not result in transmission, might have a negative effect on an infant’s health. In addition, factors that can generally have a detrimental affect on an infant’s health, such as lack of breastfeeding, unhygienic living conditions, and exposure to malaria are though to affect the infants of HIV-positive mothers to a greater degree.

Advanced maternal HIV infection is known to be associated with an increased rate of mother-to-child transmission of HIV and faster disease progression amongst infected infants.

Researchers therefore hypothesised that advanced HIV disease or immune suppression in mothers increased the rate of hospitalisation and death in their infants.

A total of 620 mother-infant pairs were recruited to the study in Lusaka, Zambia. Blood samples were obtained from the mothers on recruitment and just before delivery and CD4 cell count, haemoglobin and HIV viral load were measured. The infants had their HIV infection status checked using PCR tests one and five weeks after birth and then every three months.

Information was also obtained on the mothers’ age, income, employment and partnership status, living conditions, and food security.

The primary outcomes of the study were infant death, hospitalisation and growth by month four.

Overall infant mortality was 2% by day 28 and 5% after four months. The investigators found that a maternal CD4 cell count below 350 cells/mm³ (hazard ratio 2.87), a low maternal haemoglobin level ( below 10g/dl, hazard ratio 2.37), and a birth weight below 2500g (hazard ratio 2.43) were significantly associated with infant mortality within four months.

The risk of infant death was reduced by 70% for each 100 cell/mm3 increase in maternal CD4 cell count.

In total 39 infants were hospitalised at least once during the first four months of life. Once again, a maternal CD4 cell count below 350 cells/mm³ (hazard ratio 2.28) was found to be significant, as was not breastfeeding (hazard ratio 3.34).

Finally, the investigators looked to see if there was a relationship between infant growth and maternal HIV disease severity and immuno-suppression. The investigators found that after controlling for possible confounding factors, a maternal viral load above 100,000 copies/ml was associated with an infant weight 150g lower at month four than infants whose mothers had a viral load below this.

“Early infant mortality and severe morbidity among HIV-uninfected infants born to HIV-infected mothers were more than double when maternal CD4 cell counts were low”, write the authors, “even complete eradication of vertical transmission will not be able to counteract the full negative impact of HIV infection in reproducing women on the health of their children”, they add.