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Why do so many pregnant women get HIV?

Studies find new HIV infections in pregnant women

Most women in Africa get tested for HIV during antenatal care — if they are found to be infected, they can take antiretroviral treatment (ART) to protect their babies. But even if a pregnant woman tests HIV-negative, she can still infect her baby if she gets HIV later when she is still pregnant or breastfeeding.

To see how often pregnant women get HIV, many studies re-tested women at delivery or shortly after birth. Reports from 7 studies – 2 in eSwatini (Swaziland), 4 in South Africa, and 1 in Zimbabwe – show women getting HIV at rates >10% per year when they are pregnant or shortly after birth (Table 1). Most of these rates are reliable — from large studies 58-226 new infections.

Table 1: New infections in pregnant and post-partum women

Country, years of study[reference] Number of new HIV infections When did women get these new infections? Rate at which women got HIV (%/year)
eSwatini (Swaziland), 2004,2006[1] 226 6 months before antenatal care 19.0
eSwatini, 2008-9[2] 58 From antenatal care to delivery 16.8
Zimbabwe, 1990-93[3] 39 From antenatal care to 6 months post-partum 13.3
South Africa, 2007-8[4] 4 4 weeks before antenatal care 11.2
South Africa, 2011-12[5] 212 From antenatal care to delivery 11.2
South Africa, 2002-5[6] 81 When pregnant 11.0
South Africa, 2006-7[7] 72 During antenatal care 10.7

What did studies do to find the source of new HIV infections in pregnant women?

Trace and test sexual partners? None of these studies traced and tested any of the women’s sexual partners. Most of the women had only one partner – the father of their baby — during the time they got new infections. This was not only a scientific mistake (lazy science), but it was also an ethical “oversight.” If a husband was found to be HIV-negative, the couple should be warned to protect the husband.

Look for blood-borne risks? No one looked. No study presented any list of women’s skin-piercing procedures, such as injections, blood tests, infusions, possible wound contact with bloody clothes or gloves, etc. No study assessed infection control practices for any skin-piercing procedure or facility. No study reported looking to see if women treated at the same facilities at similar times had very similar HIV.

The rate of new infections in pregnant women vs. the % of adults with HIV

How much do new infections in pregnant women contribute to Africa’s worst epidemics? The studies in Table 1 come from 3 of the 5 countries in Africa with the worst HIV epidemics. These studies suggest that new HIV infections in pregnant women – from whatever source – make a big contribution to Africa’s worst epidemics (Table 2):

  • In eSwatini (Swaziland), 2 studies found pregnant women got HIV at rates of 16.8% and 19% per year. If women got HIV at such rates for <2 years, the percent who would be infected would be greater than the percent of all adults who are HIV-positive.
  • In South Africa, 4 studies found pregnant women got HIV at rates from 10.7% to 12.2% per year. If women got HIV at such rates for <2 years, the percent who would be infected would be greater than the percent of all adults who are HIV-positive.
  • In Zimbabwe, one study found pregnant women got HIV at 13.3% per year. If women got HIV at that rate for 1 year, the percent who would be infected would equal the percent of all adults who are HIV-positive.

 Table 2: Number of years at observed rates of HIV incidence to reach each countries average adult HIV prevalence

Country, adult HIV prevalence* in 2017[8] Year of study [reference] HIV incidence† for pregnant and postpartum women (%/year) Number of years at observed rate of incidence to reach to reach adult HIV prevalence (years)
eSwatini (Swaziland), 27.4% 2004, 2006[1] 19.0% 1.4
2008-9[2] 16.8% 1.6
South Africa, 18.8%

 

2007-8[4] 11.2% 1.7
2011-12[5] 11.2% 1.7
2002-5[6] 11.0% 1.7
2006-7[7] 10.7% 1.8
Zimbabwe, 13.5% 1990-93[3] 13.3% 1.0

* % of adults aged 15-49 years who are HIV-positive. † rate at which women get new infections (%/year or number per 100 person-years).

New HIV infections in pregnant women are hard to explain through sex. Women with HIV-positive partners have been found to get HIV at 10%/year or less in Africa and elsewhere, even when couples don’t know the wife is at risk (studies test and re-test husbands and wives, but don’t tell them if someone’s infected). Hence, observed rates of >10%/year for new HIV infections in pregnant women would be high even if all their partners were HIV-positive. But that’s absurd.

It’s reasonable to assume that when a pregnant women is HIV-negative, the percent of husbands with HIV is less the percent of all adults in a country who are infected (consider: women are more often infected than men; and many husbands who are infected have an HIV-positive wife). Hence, one could expect pregnant women would get HIV from sex rates of about:

  • 2.7%/year in Swaziland (10% of Swaziland’s 27.4% adult HIV prevalence)
  • 1.9%/year in South Africa (10% of South Africa’s 18.8% adults HIV prevalence)
  • 1.3%/year in Zimbabwe (10% of Zimbabwe’s 13.3% adult HIV prevalence)

These estimated rates are far less than rates observed in the studies reported in Table 1.

Additional information

Data in tables 1-3 are from references 1-7 and 10-17. Data in bold in these tables are estimated from reported data as explained in the Appendix Table in reference 9.

Table 3, below, reports findings from 8 other studies in 7 African countries showing pregnant women getting new infections at rates from 6.1% to 8% per year, lower than in Table 1, but so high that people should be looking closely to see if women are getting HIV from healthcare.

Table 3: New infections in pregnant and post-partum women, 8 more studies

Country, years of study[reference] Number of new HIV infections When did women get these new infections? Rate at which women got HIV (%/year)
Malawi, 1990-93[10] 27 From antenatal care to delivery 7.99
Rwanda, 1988-89[11] 8 From delivery to 6 months post-partum 7.6
South Africa, 1993[12] 4 From antenatal care to delivery 7.3
Nigeria, 2004[13] 5 From antenatal care to delivery 6.9
Cameroon, 2011-12[14] 10 From antenatal care to delivery 6.8
Kenya, 2008[15] 53 From antenatal care to 6 weeks post-partum 6.8
Ethiopia, 1995-97[16] 16 6 months antenatal care 6.3
Malawi, 2000-4[17] 11 4 weeks before antenatal care 6.1

References

1. Bernasconi D, Tavoschi L, Regine V, et al. Identification of recent HIV infections and of factors associated with virus acquisition among pregnant women in 2004 and 2006 in Swaziland. J Clin Virol 2010; 48: 180-183.

2. Kieffer MP, Nhlabatsi B, Mahdi M, et al. Improved detection of incident HIV infection and uptake of PMTCT services in labor and delivery in a high HIV prevalence setting. J Acquir Immune Defic Syndr 2011; 57: e85-e91.

3. Mbizvo MT, Kasule J, Mahomed K, Nathoo K. HIV-1 seroconversion incidence following pregnancy and delivery among women seronegative at recruitment in Harare, Zimbabwe. Cent Afr J Med 2001; 47: 115-118.

4. Kharsany ABM, Hancock N, Frolich JA, et al. Screening for ‘window-period’ acute HIV infection among pregnant women in rural South Africa. HIV Med 2010; 11: 661-665.

5. Dinh T-H, Delaney KP, Goga A, et al. Impact of maternal HIV seroconversion during pregnancy on early mother to child transission of HIV (MTCT) measured at 4-8 weeks postpartum in South Africa 2011-2012: a national population-base survey. PLoS 2015; 10: e0125525. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4420458/ (accessed 25 October 2017).

6. Wand H, Ramjee G. Combined impact of sexual risk behaviors for HIV seroconversion among women in Durban, South Africa: implications for prevention policy and planning. AIDS Behav 2011; 15: 479-486.

7. Moodley D, Esterhuizen TM, Pather T, et al. High HIV incidence during pregnancy: compelling reason for repeat testing. AIDS 2009; 23: 1255-1259.

8. UNAIDS. HIV estimates with uncertainty bounds 1990-2017. Geneva: UNAIDS, 2018. Available at: http://www.unaids.org/en/resources/documents/2018/HIV_estimates_with_uncertainty_bounds_1990- (accessed 8 November 2018).

9. Gisselquist D. Mixed signals: not investigating high HIV incidence in pregnant women in Africa, April 2018 version. SSRN 2018. Available at: https://papers.ssrn.com/sol3/papers.cfm?abstract_id=3153795 (accessed 8 November 2018).

10. Taha TE, Hoover DR, Dallabetta GA, et al. Bacterial vaginosis and disturbances of vaginal flora: association with increased acquisition of HIV. AIDS 1998; 12: 1669-1706.

11. Leroy V, Van de Perre P, Lepage P, et al. Seroincidence of HIV-1 infection in African women of reproductive age: a prospective cohort study in Kigali, Rwanda, 1988-92. AIDS 1994; 8: 983-986.

12. Qolohle DC, Hoosen AA, Moodley J, et al. Serological screening for sexually transmitted infections in pregnancy: is there any value in re-screening for HIV and syphilis at the time of delivery? Genitourin Med 1995; 75: 65-67.

13. Sagay AS, Musa J, Adewole AS, et al. Rapid HIV testing and counseling in labor in a northern Nigerian setting. Afr J reprod Health 2006; 10: 76-81. Available at: https://www.ajol.info/index.php/ajrh/article/view/7878/1505 (accessed 1 October 2017).

14. Egbe TO, Tazinya R-MA, Halle-Ekane GE, et al. Estimating HIV incidence during pregnancy and knowledge of prevention of mother-to-child transmission with an ad hoc analysis of potential cofactors. J Pregnancy 2016, article ID 7397695. Available at: https://www.hindawi.com/journals/jp/2016/7397695/ (accessed 22 September 2017).

15. Kinuthia J, Kiarie JN, Farquhar C, et al. Cofactors for HIV-1 incidence during pregnancy and postpartum period. Curr HIV Res 2010; 8: 510-514.

16. Wolday D, Meles H, Hailu E, et al. Temporal trends in the incidence of HIV infection in antenatal clinic attendees in Addis Ababa, Ethiopia, 1994-2003. J International Med 2007; 261: 132-137. Available at: http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2796.2006.01740.x/abstract (accessed 20 October 2017).

17. Gay CL, Mwapasa V, Murdoch DM, et al. Acute HIV infection among pregnant women in Malawi. Diagn Microbiol Infect Dis 2010; 66: 356-360. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2864613/ (accessed 27 June 2017).

 

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