HIV incidence and retesting in pregnancy
Polly Clayden, HIV i-Base
Several groups have documented high rates of HIV acquisition during pregnancy and breastfeeding.
Two oral presentations at CROI showed findings from investigations into HIV incidence and retesting among women in high prevalence settings in Africa.
John Kinuthia from the University of Nairobi, Kenya presented data from a study looking at HIV incidence among mothers accompanying their infants for routine 6-week immunisation at 6 maternal–child health clinics in Nairobi and Nyanza Province of Western Kenya. 
In this study, mothers completed a questionnaire, before their HIV test, that assessed sociodemographic characteristics, obstetric history, HIV risk perception, and participation in PMTCT programmes during their last pregnancy. The investigators compared characteristics of HIV-negative women who seroconverted during pregnancy and immediately post partum to those who did not.
Dr Kinuthia reported that 2035 out of 2135 (95.3%), mothers who had tested HIV-negative in pregnancy, accepted a repeat HIV test at the immunisation visit. Of these, 53 (2.6%) were HIV-positive, giving an overall estimated HIV incidence of 6.8 (95%CI 5.1–8.8) per 100 woman-years.
The mean age of the mothers was 23.7 years. Of these 86.8% were married, 7.1% in polygamous marriages and 29.4% were employed.
Mothers who seroconverted were more likely to be employed (45.3% vs 29.0%, p=0.01), married (96.2 vs 86.6%, p=0.04) and from a higher HIV prevalence region (60.4% in Nyanza vs 28.8% in Nairobi, p<0.001).
Married women, in a polygamous relationship were significantly more likely to seroconvert (19.6% vs 6.7%, p<0.001). Age, educational level, HIV risk perception, history of physical assault, and economic status were not associated with seroconversion. In multivariate analysis, region (OR 3.6; 95%CI 2.1–6.4, p<0.001) and employment (OR 1.9; 95%CI 1.1–3.3, p=0.03) were independent predictors of seroconversion.
Dr Kinuthia suggested that the limitations of the study included no data on the timing of the mothers’ initial HIV test, nor their partners’ status.
He concluded that repeat HIV testing in early postpartum was highly acceptable and resulted in detection of substantial HIV incidence. He noted that the incidence in pregnancy and early postpartum in this study compared to that among cohorts of sex workers and women in discordant relationships. He stressed the need for an urgent review of services for negative pregnant women in regions with high HIV seroprevalence and interventions such as couple counselling and testing, the promotion of safer sex in pregnancy and awareness of the risk of infection and in turn MTCT.
Following on from this was a presentation from Mary Pat Kieffer from the Elizabeth Glaser Pediatric AIDS Foundation, showing data from a study in which retesting in maternity facilities was used to provide interventions for women who became infected late in pregnancy. 
Swaziland has a very high rate of HIV prevalence among pregnant women (42%) and a high uptake of PMTCT.
The primary objective of the study was to evaluate the effectiveness of a provider focused intervention in increasing ARV coverage at time of delivery. As secondary objectives the investigators sought to determine HIV incidence in late pregnancy and the number of newly-indentified HIV-positive women in maternity. They also looked at whether provision of nevirapine to women who refused testing increases coverage.
Maternity staff received an extra one-day training based on the women’s status on arrival. This included:
• Testing women with unknown status and offering nevirapine (NVP) to those who declined.
• Routine HIV retesting as standard of care for women who tested negative three months or more earlier (Swazi guidelines).
• Ensuring all newly identified women receive ARV treatment or prophylaxis.
Women received antiretrovirals in accordance with Swazi national guidelines (NVP+3TC+AZT for women meeting criteria for treatment or short course AZT plus single dose NVP and AZT+3TC “tail” prophylaxis for healthier women).
Sampling used 6 public maternity sites, matched as pairs and randomised within the pair to intervention or control.
Data on testing and ARV prophylaxis were collected through questionnaires and MoH registers.
Cord blood samples were collected as dried blood spots (DBS) and tested for HIV. All positive DBS were tested for NVP. Coverage was defined as number of cord bloods with detectable NVP.
The investigators found 1398/2444 (62.3%) women enrolled in the study had previously tested negative in pregnancy.
Overall NVP was detected in 75% cord bloods, this was significantly higher in the intervention than the control groups, 80% vs 69%, p=0.0001. Dr Kieffer noted that the only group of women for whom there was no significant improvement was those who already knew their status and had taken their ARV prophylaxis at home (p=0.23).
The most critical finding of this study was the high level of HIV incidence in pregnancy: 4.4% women who were HIV negative in ANC were positive at time of delivery giving a rate of 16.75 new infections per 100 person-years. Dr Kieffer suggested that, like the previous data from Nyanza, this rate is similar to cohorts of sex workers and IDU.
She compared these rates to earlier data from Rakai that showed 1.1 per 100 person years incidence in non-pregnant women vs 2.3 in pregnant women per 100 person years.
The second critical finding was that ARV provision almost doubled for women who seroconverted during pregnancy (n=58), 26% vs 54% in control vs intervention groups respectively (p=0.03).
Dr Kieffer explained that this was still only reaching about half those that seroconverted. Control sites had retested 14% (135/ 959) HIV–negative women, compared to 45% (528/1185) women at intervention sites p<0.0001; relative risk 3.17 (95%CI 2.67–3.74). The primary reason for this was the Swazi guidelines only recommend retesting after 3 months or more, but a significant proportion of women (38%) had been previously tested for HIV earlier than this so were not eligible for retesting.
“Reaching women who become infected late in pregnancy cannot be an afterthought for PMTCT programmes” she said.
Like the previous study these data highlight the need for interventions to identify and provide ARV prophylaxis to women who seroconvert in pregnancy and prevention strategies to enable HIV-negative women to remain negative.
This issue is important and was also raised by Lu et al at CROI last year. 
The question of poor test performance discussed by Black et al in AIDS was also discussed following the presentation. 
Whether these transmissions can be attributed to HIV incidence in pregnancy or poor test performance, unidentified HIV positive women in pregnancy remain a barrier to the eradication of paediatric HIV.
Unless stated otherwise, all references are to the Programme and Abstracts of the 17th Conference on Retroviruses and Opportunistic Infections. 16-10 February 2010, San Francisco. All oral abstracts are available as webcasts.
- Kinuthia J et al. Co-factors for HIV Incidence during Pregnancy and the Postpartum Period. 17th CROI, San Francisco, 2010. Oral abstract 155.
Webcast: Treatment outcomes in women and children. Friday 9.30am.
- Kieffer MP et al. Repeat HIV testing in labor and delivery as a standard of care increases ARV provision for women Who Seroconvert during Pregnancy. 17th CROI, San Francisco, 2010. Oral abstract 156.
Webcast: Treatment outcomes in women and children. Friday 9.30am.
- High rates of HIV acquisition in pregnancy and post partum in Francistown, Botswana. HTB April 2009.
- Black V et al. High HIV incidence or poor test performance? AIDS, 23 October 2009. Vol 23; (16) p2234-2235.