Illness in pregnancy and bacterial vaginosis increase risk of HIV transmission in the womb

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Illness early in pregnancy and bacterial vaginosis are both associated with mother-to-child transmission of HIV in the womb, investigators report in the January 2nd 2010 edition of AIDS.

The use of antiretroviral treatment during pregnancy and the avoidance of breastfeeding can cut the risk of mother-to-child transmission of HIV. Such interventions are now widely implemented and it is estimated that between 20-50% of the transmissions that still occur take place in the womb (or in-utero).

Previous research has identified viral load, lack of antiretroviral treatment during pregnancy, and low birth weight as risk factors for HIV transmission in the womb.

Glossary

mother-to-child transmission (MTCT)

Transmission of HIV from a mother to her unborn child in the womb or during birth, or to infants via breast milk. Also known as vertical transmission.

cervix

The cervix is the neck of the womb, a tight ‘collar’ of tissue that closes off the womb except during childbirth. Cancerous changes are most likely in the transformation zone where the vaginal epithelium (lining) and the lining of the womb meet.

deoxyribonucleic acid (DNA)

The material in the nucleus of a cell where genetic information is stored.

in utero

Latin term meaning in the womb.

monotherapy

Taking a drug on its own, rather than in combination with other drugs.

Researchers in Kenya wished to gain a better understanding of the factors associated with in-utero HIV transmission.

Their research was conducted between 1999 and 2002 and involved 463 HIV-infected women.

Treatment to prevent transmission of HIV to infants consisted of AZT-monotherapy which was started in the 34 – 36 week of pregnancy.

Routine care during pregnancy included screening for sexually transmitted infections and bacterial vaginosis.

HIV transmission in the womb was defined as a positive test for HIV’s genetic material – DNA or RNA – less than 48 hours after birth.

There were 88 (19%) cases of mother-to-child transmission of HIV. Of these, 29 (33%) were HIV DNA or RNA-positive less than 48 hours after birth and were therefore infected with the virus in the womb.

The characteristics of the mothers and infants where in utero transmission of HIV occurred were compared to those when there was either no HIV transmission or transmission occurred because of breastfeeding.

Maternal viral load in both blood (p <0.001) and cervical fluids (p = 0.004) was one-half log10 higher in the women who transmitted compared to mothers whose infants were uninfected.

CD4 cell percentage was also significantly lower in the mothers who passed on HIV to their infants in the womb (20% vs. 24%, p = 0.01).

In-utero HIV transmission was also associated with shorter duration of AZT monotherapy, and 57% of the mother who transmitted the virus in this way received less than three weeks of treatment.

Infants infected in the womb had a lower birth-weight (2.9 vs. 3.1 kg, p < 0.001) and gestational age ( 38.5 vs. 39.3 weeks, p = 0.02).

Bacterial vaginosis was diagnosed in 59% of the women who transmitted the virus in-utero compared to 35% of women who did not, a significant difference (p = 0.02).

Transmitting women were also more likely to have had an AIDS-defining illness in the past year, and to have been ill early in pregnancy experiencing diarrhoea, cough, or fever.

Statistical analysis showed that higher viral load in both blood and cervical secretions (p < 0.05), shorter duration of AZT treatment (p = 0.04), illness during pregnancy (p = 0.01) and bacterial vaginosis (p = 0.01) were all significantly associated with HIV transmission in the womb.

“To our knowledge, neither illness in early pregnancy nor bacterial vaginosis has been reported as a risk factor for transmission in utero”, write the investigators.

They suggest that illness during pregnancy could cause a transient increase in viral load and fall in CD4 cell count. The association with bacterial vaginosis is likely to be explained, they add, by the presence of organisms in the upper genital tract.

“As both illness in early pregnancy and bacterial vaginosis are amenable to interventions, these data suggest additional means to target the in-utero period, a period that is likely to increase in relative significance”, conclude the investigators.

References

Farquhar C et al. Illness during pregnancy and bacterial vaginosis are associated with in-utero HIV-1 transmission. AIDS 24: 153-55, 2010.