Why isn't there 100% transmission of HIV from an HIV-infected mother to fetus?

[BlondeCookie]

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The evidence bears that there is only about around 25% chance of transmitting HIV from an HIV-infected mother to fetus. I was wondering why this isn't 100% since HIV is one of only a few viruses that crosses the placenta.
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[ZonaRidicularis]

z

 

[bambi]

The evidence bears that there is only about around 25% chance of transmitting HIV from an HIV-infected mother to fetus. I was wondering why this isn't 100% since HIV is one of only a few viruses that crosses the placenta.
😕

It isn't anything like as high as 25%.

 

[peter90036]

maybe the baby's immune system isnt 'mature' enough to be infected?
...when do lymphocytes get all those CDs?

 

[Pinkertinkle]

Nothing's 100% in medicine.

 

[pseudoknot]

The evidence bears that there is only about around 25% chance of transmitting HIV from an HIV-infected mother to fetus. I was wondering why this isn't 100% since HIV is one of only a few viruses that crosses the placenta.
😕

HIV is very fragile and inefficiently transmitted by any means. This may partly explain it.

 

[bambi]

With drugs and a good c section transmission is closer to 1%. It may be possible for it to cross the placenta but in reality this rarely happens. Even with transfusions of infected blood transmission isn't 100%, it's around 80-90%.

 

[dbhvt]

With drugs and a good c section transmission is closer to 1%. It may be possible for it to cross the placenta but in reality this rarely happens. Even with transfusions of infected blood transmission isn't 100%, it's around 80-90%.

In the US, C-section no longer recommended if viral load is suppressed. hasn't been for a while.

 

[bambi]

In the US, C-section no longer recommended if viral load is suppressed. hasn't been for a while.

Well it should be! I imagine it's a money thing, pretty sure it still is over here.

 

[dbhvt]

Well it should be! I imagine it's a money thing, pretty sure it still is over here.

Ummm, no, it's a surgery is risky thing. Who's teaching you guys this? The problem is that you have all these studies being done about reducing MTCT in resource poor areas--they make it into JAMA and NEJM, and it's easy to just skim the abstract and miss the context. Apparently we have some professors out there that aren't paying attention. If viral load is undetectable, peripartum MTC transmission is not reduced by c-section vs. vaginal delivery. Risk of transmission is 1-2% regardless. Risk of any morbidity/mortality, probably higher with c-section, but I haven't read that study. Oh, also, there are slightly different protocols for vaginal delivery in an HIV+ woman--avoid routine episiotomy, etc.

Elective cesarean section tended to be inversely associated with MTCT in the overall population, but not in mothers who delivered at term with viral load < 400 copies/ml [odds ratio (OR), 0.83; 95% CI, 0.29-2.39; P = 0.37]. Among them, only duration of antenatal therapy was associated with transmission (OR by week, 0.94; 95% CI, 0.90-0.99; P = 0.03).

Mother-to-child HIV transmission despite antiretroviral therapy in the ANRS French Perinatal Cohort.
AIDS. 2008 Jan 11;22(2):289-99.
PMID: 18097232

There are some authors out there that disagree, but their statistics don't support their disagreement.

 

[docmd2010]

I would tend to agree with the above. HIV is a rather weak virus and maybe antibodies crossing the placenta from the mother are enough to destroy the virus.

 

[bambi]

Ummm, no, it's a surgery is risky thing. Who's teaching you guys this?

Well, haven't touched on it much in med school yet actually but during my immunology degree we were certainly taught that C-section is definitely preferred and in the UK any pregnant HIV positive woman would be offered one. Yes surgery is risky but so is giving birth.

 

[bambi]

I would tend to agree with the above. HIV is a rather weak virus and maybe antibodies crossing the placenta from the mother are enough to destroy the virus.

In that case transmission would be zero which it isn't.

 

[ZonaRidicularis]

z

 

[PhDtoDO]

Well it should be! I imagine it's a money thing, pretty sure it still is over here.

Cesarians actually are well known to increase the likelihood of transmission from mother to child. It has been heavily studied and demonstrated, hence the change in policy/recommendations.

 

[pseudoknot]

Cesarians actually are well known to increase the likelihood of transmission from mother to child. It has been heavily studied and demonstrated, hence the change in policy/recommendations.

Sorry, that's the opposite of the truth.

http://www.ncbi.nlm.nih.gov/pubmed/10199349
http://www.ncbi.nlm.nih.gov/pubmed/16235405
http://www.ncbi.nlm.nih.gov/pubmed/11131694

 

[Captopril]

HIV has an extremely high ID50...you need one billion zillion viral units to get the infection.