IAS: PrEP and timed intercourse reduces HIV transmission risk associated with natural conception

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“Millions” frustrated with assisted reproduction

Assisted reproduction techniques have been helping mixed-status heterosexual couples conceive safely since 1992. When the male is HIV-positive, this usually involves ‘sperm washing’ and artificial insemination.

In reality, however, many mixed-status couples are having unprotected intercourse in the hopes of natural conception – a practice which exposes the HIV-negative partner to the risk of infection. In many cases this often stems from frustration with safer techniques which can be expensive and hard to access.

“The number of HIV-discordant couples worldwide practising unprotected sex for the purpose of conception could number in the millions,” wrote Dr Pietro Vernazza of St Gallen Cantonal Hospital, Switzerland in a commentary in the journal AIDS last year. And a recent survey of 500 mixed-status couples found that “almost half of the couples who did not conceive with artificial insemination attempted spontaneous conception through unprotected intercourse, and at least one infection occurred.” (Barriero 2006)

On the other hand, a recent Spanish study investigated 62 couples in which one partner (22 of whom were women and 40 of whom were men) was HIV-positive and on antiretroviral treatment, with undetectable viral load in the blood. Among 76 natural pregnancies in these couples over a seven-year span, none of the uninfected partners seroconverted.


prospective study

A type of longitudinal study in which people join the study and information is then collected on them for several weeks, months or years. 

pilot study

Small-scale, preliminary study, conducted to evaluate feasibility, time, cost, adverse events, and improve upon the design of a future full-scale research project.



The fluid portion of the blood.


A chemical messenger which stimulates or suppresses cell and tissue activity. Hormones control most bodily functions, from simple basic needs like hunger to complex systems like reproduction, and even the emotions and mood.


A serodiscordant couple is one in which one partner has HIV and the other has not. Many people dislike this word as it implies disagreement or conflict. Alternative terms include mixed status, magnetic or serodifferent.

A small Swiss study presented on Monday to the Fourth IAS Conference in Sydney, suggests that HIV-negative women may be able to conceive safely by having unprotected intercourse with their HIV-positive male partner – as long as the partner’s seminal viral load is undetectable. A combination of couples counselling, STI screening, and timed intercourse – with the “psychological safeguard” of two doses of tenofovir (Viread) as pre-exposure prophylaxis (PrEP) – has resulted in a pregnancy rate of over 70%, and no HIV transmission.

PrEP primarily a “psychological safeguard”

During the question and answer session that followed, Dr Vernazza said he considered PrEP to be an additional risk-lowering intervention but that it was primarily used as a “psychological safeguard. There’s a lot of psychological issues in there [for the couples],” he said. “I tell them that the [HIV transmission] risk is small – between in one in one-hundred thousand and one in a million – but they have practiced safer sex for so many years in the belief that there is a big risk, so they want to have this safeguard.”

He added that the risks and benefits of this method, compared with traditional assisted reproduction, were explained in an hour-long counselling session, and that most couples were convinced enough to try it. “It is taking longer to persuade some physicians,” he noted, adding, however, that there was worldwide interest in their timed intercourse methods.

Indeed, in an interview in the forthcoming August/September issue of AIDS Treatment Update, Dr Carole Gilling Smith, who runs the Viral Illness Fertility Programme at London’s Chelsea & Westminster Hospital, says it is crucial to acknowledge the reality that there are couples who will use natural conception methods over assisted methods. “Over the next several years it’s going to be important to look at natural conception risks and how they compare to current standards,” she says. “It is certainly difficult ground ethically, but given that people are choosing natural conception, we should study it without actively encouraging it until we have more evidence of its safety.”

Dr Vernazza told the conference that they were now planning a prospective study which would also measure the couples’ subsequent condom use. “At the moment,” he said, “we cannot say whether condom use has changed [following the intervention]. But it is certainly a concern.”

Sperm washing “no longer appropriate” with undetectable viral load

Dr Vernazza told the conference today that he and some other European assisted reproduction specialists have concluded that “sperm washing is no longer appropriate” when the male has an undetectable seminal viral load. “With a suppressed viral load in semen the risk [of HIV transmission] is getting towards zero,’ he said, “and is probably very, very close to zero.”

Consequently, Dr Vernazza and colleagues set up a pilot programme that offered an alternative method of risk reduction utilising modified natural conception techniques. Twenty-two couples were enrolled between March 2004 and March 2007; six admitted that they had previously tried to conceive by unprotected intercourse, and 21 agreed to use the proposed risk reduction strategy. All the HIV-positive male partners were on antiretroviral therapy with undetectable viral loads in both plasma and semen.

Following couples counselling, and STI screening in both partners, intercourse was recommended to take place on the single day when the chance of pregnancy was highest – 36 hours after peak levels of luteinising hormone (LH). The HIV-negative female partners received two single doses of tenofovir as PrEP, at the LH peak and 24 hours later (36 hours and twelve hours before intercourse).

After three attempts at conception using this method, eleven of the 21 women (52%) became pregnant. This increased to 15 of the 21 (71%) after ten attempts. All of the women tested HIV-antibody negative three months after their last exposure.


Vernazza P et al. Pre-exposure prophylaxis and timed intercourse for HIV-discordant couples willing to conceive a child. Fourth IAS Conference on HIV Pathogenesis, Treatment and Prevention, Sydney, abstract MOPDC01, 2007.

Vernazza P et al. HIV-discordant couples and parenthood: how are we dealing with the risk of transmission? AIDS 20(4): 635-636, 2006.

Barreiro P et al. Natural pregnancies in HIV-serodiscordant couples receiving successful antiretroviral therapy. J Acquir Immune Defic Syndr. 43(3): 324-326, 2006.