Pregnancy

Since 1999 it has been routine for pregnant women in the UK to be offered an HIV test. The test was introduced in recognition of the fact that there are effective methods of preventing vertical transmission and effective treatments for adults.

In the mid-1990s only about one-third of infected pregnant women were diagnosed, and most of those were aware of their infection status before they became pregnant.¹

Debate about how the test should be offered was influenced by two studies in Edinburgh, where different methods were compared. The first, randomised study found that uptake of testing was 6% when testing information was provided in leaflets, but rose to 35% when a midwife directly offered the test.² The uptake of testing varied between midwives, suggesting that midwives' own attitudes towards offering the test affected the response of patients. It was also found that routine testing did not provoke any more anxiety amongst pregnant women than other routine blood tests offered during pregnancy.

That study used an opt-in approach (women had to make an active choice to be tested), and some women felt that to opt in would indicate high-risk behaviour. The second study³ assessed an opt-out approach (midwives offered the test orally, emphasising its benefits, the fact that it was routine, and the possibility that women could opt out if they wished). In this study, 88% of women accepted the offer of a test. 

In 1999, the government announced that HIV testing would be offered and recommended routinely to all pregnant women in the UK, and this policy was fully implemented by 2003.

This is often cited as a major success in testing policy: there has been a significant reduction in the proportion of HIV infections that remain undiagnosed before delivery; and women who are tested antenatally have a higher median CD4 count at diagnosis than other women and heterosexual men, which would indicate that efforts to detect HIV infection in people without symptoms will result in earlier diagnosis, reduced morbidity and mortality, and less onward transmission.

There have been cases of women who have tested negative early in their pregnancy, but were either tested during the window period or seroconverted during pregnancy or while breastfeeding, and subsequently passed their infection onto their baby (a high viral load in acute infection is likely to be a contributory factor).^4,5 BHIVA pregnancy guidelines suggest that in specific cases where a woman is at continued high risk of HIV infection, it may be appropriate for her to be offered a further HIV test during the third trimester.⁶

To deal with the same problem, American researchers have argued that as well as retesting during the third trimester, pooled RNA tests should be used. These have a significantly shorter window period: in North Carolina 3.4% of positive women would have had their diagnosis missed if only antibody tests were used.⁷ 

BHIVA guidelines also recommend that if a woman arrives for labour without previous contact with antenatal services, a rapid test should be offered.

Routine testing does means that some woman will receive their diagnosis in pregnancy. For a newly diagnosed pregnant woman her HIV diagnosis is likely to be shocking and will provoke anxiety. She will have concerns about her health, the health of her baby and the HIV status of her partner. Women in this situation will be required to make complex decisions about treatment, prevention of mother-to-child transmission and – potentially – disclosure of her status to her baby’s father. She should be offered care from an obstetrician experienced in this field and an HIV consultant.