Can the risk of transmission during birth be reduced?

Published: 01 June 2012

The effect of antiretroviral therapy at the time of delivery is discussed later in the chapter.

A planned caesarean section, conducted before labour has started and before the membranes (‘waters’) have ruptured, or ‘broken’, is considered an effective way to prevent mother-to-child transmission during delivery. A systematic review conducted in 2005, looking at both a randomised clinical trial and a number of observational studies, concluded that an elective caesarean section was an effective intervention.1 The randomised clinical trial found that, out of 436 HIV-positive women, transmission took place in three out of 170 caesarean births, or 2%, whereas it occurred in 21 of 200 vaginal births, or 11%. (There were also differences in HIV treatment so the observed difference may not have been just due to the mode of delivery.)

However, the review also suggested that the mode of delivery chosen should be assessed in the light of risks as well as benefits, and suggested that an elective caesarean section was most useful for women who were not on treatment during their pregnancy, or taking only AZT (zidovudine, Retrovir). A 2007 review similarly found elective caesarean section was more effective in preventing transmission than a vaginal delivery, but suggested that its role was most useful in cases where viral load had not been completely suppressed.2  

In a French cohort of almost 3000 women who gave birth with a viral load below 400 copies/ml, the risk of transmission was 0.6%, and did not vary according to mode of delivery.3 Similarly, in the UK and Ireland cohort of over 2000 women who gave birth with a viral load below 50 copies/ml as a result of combination therapy, there were three infections. Two were in babies born by planned caesarean and one in a baby born by planned vaginal delivery, and the study concluded there was no difference in the risk of transmission. For women on combination therapy (but not necessarily undetectable), the transmission risk was 0.7% for both planned caesarean and vaginal deliveries.4

Current UK guidelines on the management of HIV infection in pregnant women, prepared by BHIVA and CHIVA in 2008,5 advise that the decision about the mode of delivery – as with other care – should be tailored to the woman’s individual clinical situation. The guidelines state that the decision should be taken by the mother, the obstetrician and the HIV physician, in a detailed risk assessment. This should take into account such factors as her treatment history, her viral load, and when in her pregnancy she first presented to the HIV and/or antenatal clinic. It should also consider the woman’s wishes, and what her plans for further pregnancies might be. For example, if a woman may be returning to a country where elective caesareans would not be readily available for potential future deliveries, it may be more appropriate for her to have a vaginal delivery.

In all cases where a woman’s most recent viral load is detectable at more than 50 copies/ml, or her viral load is unknown at week 38 of her pregnancy, a pre-labour caesarean, plus intravenous AZT is recommended. A vaginal birth can be considered for women on stable therapy whose viral load is undetectable.4 

Below is a summary of the BHIVA/CHIVA guidelines on mode of delivery.

Delivery by elective caesearean section

Timing of the caesarean is, according to the guidelines, a balance between the likelihood of transient tachypnoea (a treatable lung disease in newborn babies; those born prematurely and by caesarean are at higher risk) and the risk of labour starting before the scheduled caesarean date. If the mother is on successful HIV treatment, the viral load is undetectable and there are no other reasons for choosing a caesarean, it is reasonable to schedule the operation for week 39 of the pregnancy (as with elective caesareans in the general population).

Managing a vaginal delivery

If a woman is planning a vaginal delivery, it is better that labour starts spontaneously rather than by induction. The mother and the baby will be monitored to ensure they are both coping. BHIVA/CHIVA recommend that a quick decision is made to do a caesarean if there are any concerns or progress is slow.

Foetal blood sampling and monitoring through foetal scalp electrodes should not be used.

Pre-term or delayed delivery

If a woman has a detectable viral load, or if there is a clinical reason to predict that a woman will go into labour early, a caesarean should be scheduled for 38 weeks’ gestation.

If a woman does show signs of going into labour early, it should be managed as it would be in any case of possible premature labour, along with continuation of any appropriate HIV treatment, according to the situation. See Choosing a regimen: 6. Where there is a risk of premature labour and/or rupture of membranes for more detail on how this situation will be managed.

There is conflicting evidence as to whether taking HIV treatment before conception or during pregnancy increases the likelihood of problems such as prematurity. 

A study reported in April 2009 showed that there was a significantly increased risk (five-fold) of premature labour and delivery in women who were already on anti-HIV drugs when they became pregnant.6 There was also an increased risk of low birth weight. These risks were associated with a high viral load and high blood pressure and the study concluded that women who become pregnant while on HIV treatment should be monitored carefully for these risk factors.

But research reported in May 2009 has suggested that potent HIV treatment does not affect the growth of the foetus in the womb.7

And a 2007 analysis from the Women and Infants Transmission Study found that the benefits of combination antiretroviral therapy outweighed the observed risks.8

Detailed information on HIV treatment and premature delivery can be found in NAM’s HIV Treatments Directory or at

Managing a ‘prolonged’ pregnancy (one that goes past 41 weeks’ gestation) is considered difficult in HIV-positive women. In the general population, induction of labour would usually be considered at 41 weeks, and this is often done by artificially rupturing the membranes (ARM), and/or the use of drugs. It is believed that ARM may increase the risk of mother-to-child transmission, particularly if the woman has a detectable viral load. There is also a risk that the act of rupturing the membranes will cause a trauma to the baby’s scalp, increasing the risk of exposure to infected blood and other body fluids.

Again, healthcare staff will weigh up the risks and benefits of inducing labour against possible complications of the pregnancy continuing. If the mother is on successful HIV treatment, the viral load is undetectable and is keen to try a vaginal delivery, doctors may consider inducing labour, but in most cases it is recommended that a planned caesarean is done if labour has not started by 41 weeks.


  1. Read JS, Newell ML Efficacy and safety of cesarean delivery for prevention of mother-to-child transmission of HIV-1. Cochrane Database of Systematic Reviews 2005, Issue 4, art. no. CD 005479. DOI: 10.1002/14651858, 2005
  2. Volmink J, Marais B HIV: mother-to-child transmission. Elective caesarean section. Clinical Evidence, BMJ Publications, 2008
  3. Warszawski J et al. Mother-to-child HIV transmission despite antiretroviral therapy in the ANRS French Perinatal Cohort. AIDS 22:289-299, 2008
  4. Townsend C et al. Low rates of mother-to-child transmission of HIV following effective pregnancy interventions in the United Kingdom and Ireland, 2000-2006. AIDS 22: 973-981, 2008
  5. de Ruiter A et al. British HIV Association and Children's HIV Association guidelines for the management of HIV infection in pregnant women 2008. HIV Med 9: 452-502. Available online at, 2008
  6. Machado ES et al. Pregnancy outcome in women infected with HIV-1 receiving combination antiretroviral therapy before versus after conception. Sex Transm Infect 85: 82-87, 2009
  7. Briand N et al. No relation between in-utero exposure to HAART and intrauterine growth retardation. AIDS 23 (online edition), 2009
  8. Watts DH et al. Assessment of birth defects according to maternal therapy among infants in the Women and Infants Transmission Study. J Acquir Immune Defic Syndr 443: 299-305, 2007
This content was checked for accuracy at the time it was written. It may have been superseded by more recent developments. NAM recommends checking whether this is the most current information when making decisions that may affect your health.
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