Timing of HIV transmission

Transmission of HIV via breast milk may occur at any time and the risk increases with the duration of breastfeeding.

A number of studies report a transient increase in viral load after childbirth, which could be associated with a higher risk of transmission via breastfeeding during this period. Retrospective analysis of data has found evidence that babies are more at risk of contracting HIV from breast milk early in life.1. This was confirmed in a studies from Malawi and Kenya.2 3 However, these findings should be interpreted with caution because current HIV testing technology makes it difficult to determine for certain whether an infant has been infected during delivery or by breastfeeding shortly after birth.

The Malawian study also found that women with fewer than four previous births were more likely to transmit HIV through breast milk than women who had four or more live births. Similarly, young mothers were more likely to transmit through breast milk than older mothers. The authors speculate that this may be due to 'less experienced' mothers being more likely to be affected by mastitis.2

A meta-analysis of data from nine mother-to-child transmission studies involving over 5000 infants has found that over 1500 infants were breastfed and that breastfeeding continued for an average of 6.8 months. The number of HIV infections definitely attributed to breastfeeding was 179, giving a rate of 12%. HIV transmission occurred before four weeks of age in 64% of cases.4

Despite the evidence of an elevated risk of transmission shortly after childbirth, a meta-analysis of nine major studies of mother-to-child HIV transmission has shown that there is a significant and sustained risk of late HIV transmission to breastfed children. Of the over 4000 children included in the analysis, 58% of the infected children acquired infection by day 28. The risk of late postnatal transmission continued throughout the breastfeeding period and was relatively constant. The risk for transmission was significantly higher among male infants and infants born to women with lower CD4 cell counts.5

References

  1. Dunn DT et al. Mother-to-child transmission of HIV: implications of variation in maternal infectivity. AIDS 12: 2211-2216, 1998
  2. Miotti PG et al. HIV transmission through breastfeeding. JAMA 282: 744-749, 1999
  3. Rousseau CM et al. Longitudinal analysis of HIV type-1 RNA in breast milk and its relationship to infant infection and maternal disease. J Infect Dis 187: 741-46, 2003
  4. Read JS et al. Breastfeeding and late postnatal transmission of HIV-1: an individual patients data meta-analysis (Breastfeeding and HIV International Transmission Study). Fourteenth International AIDS Conference, Barcelona, abstract TuOrB1143, 2002
  5. Bulterys M et al. Combination antiretroviral therapy in African nursing mothers and drug exposure in their infants: new pharmacokinetic and virologic findings. J Infect Dis 192: 709-712, 2005
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