Academic Day Seminars

ADS – Prevention of Perinatal HIV Transmission

This was an interesting ADS to learn about perinatal HIV transmission. This has come up a few times throughout my residency  so it was useful to have a more detailed discussion about this.


  • 3rd trimester is higher risk for in utero infection because the placental integrity is at its weakest
  • Our data tells us:
    • <1000 viral load (not ON ART) – transmission risk: 9.8%
    • <1000 viral load (on ART) –  transmission risk: 1%
      • This shows us that ART is beneficial beyond just lowering the viral load –> mechanism is not totally elucidated at this point.
  • In general we wait until day 27/28 to start if we can.
  • CD4< 200 we start right away
  • Latest we want to wait to start 28 week cut off and generally the HAART takes 3-4 decrease to have one log decrease (so those with a high viral load you will need time to get them suppressed).
  • Raltegravir (integrase inhibitor): drug brings the viral load down quickly (within 1-2 weeks) — but not the greatest pregnancy data
  • To prevent the emergence of resistance we add the lamivudine for 2 weeks to cover the time of nevirapine (long t1/2 b/c it is present for 2 weeks too) so it acts like a three drug regimen for the first two weeks of prophylaxis. Not a perfect science but this is the reason we do it here. Not all centers do this.
  • The thought regarding resistance is that the non-resistance viruses are the ones that are more likely to be transmitted in pregnancy.
    • Exception: nevirapine –> this is when you would consider raltegravir (but its a SAP product…and time is of the essence!)
  • STIs are a two-fold risk: firstly indicates a more “high-risk” behaviour, secondly the STI can change the vaginal mucosa and can promote for HIV to activate
  • Window period: can start testing around 1 week for the individual RNA NAAT, around 3 weeks for POC HIV test. So need to appreciate the clinical context of when you’re testing in relation to when the exposure is.
  • PO nevirapine can be utilized because of practicality (hard to find veins esp. in our IVDU) – but can cause NVP resistance mutations (15%) at 6 weeks in women
    • In these women (in CND) we give everyone IV zidovudine if we can and the layer in PO nevirapine as well.
      • We might use combivir (zidovudine/lamivudine) PO as “tail therapy”
    • Give infants intensified prophylaxis (zidovudine + nevirapine + lamivudine)


Overall a great ADS! Looking forward to part 2 with Carlo on peds HIV!


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