Reasons for mother to child transmission in England
Polly Clayden, HIV i-Base
Despite universal recommendation of HIV testing for all pregnant women (since 2000 in England and all UK and Ireland since 2003); high uptake of diagnoses and interventions; and very low transmission rate (about 1%), approximately 40 HIV-positive infants are born in the UK and Ireland every year.
A poster from Pat Tookey and co-workers reported findings from an audit conducted to explore the circumstances surrounding cases of mother to child transmission (MTCT) in England 2002-2005.
Surveillance data from the National Study of HIV in Pregnancy and Childhood (NSHPC) was used. Notifying clinicians were asked to complete a comprehensive audit form including details of antenatal testing, resistance testing, other pregnancy details, concurrent infections and social circumstances. An advisory group made recommendations of strategies that might reduce future transmission rates.
The investigators found that there were 3553 births in 2002-2005 to HIV-positive women in England reported by June 2008. Of these, at the time of the audit, 87 infants were known to be infected (See Table 1).
Table 1: HIV-exposed and infected infants in the UK 2002-2005
|Exposed infants reported by 2008||617||865||986||1085||3553|
|Infected infants in audit||30||22||23||12||87|
|Infected reported subsequently||3||4||10||18||35*|
* 8 infants born to diagnosed and 27 to undiagnosed women
NSHPC data were available for all 87 infants and audit forms were returned for 83 (93%). The investigators divided the infants into: those whose mothers were diagnosed before or during this pregnancy, or within two days of delivery (diagnosed group), and those who presented subsequently and whose mothers had not been diagnosed (undiagnosed group).
Of the diagnosed group (n=33) the investigators identified one or more factors that were likely to have contributed to transmission. 11/22 infants, were PCR-positive at <48 hours, which suggested in utero transmission.
Additional significant factors included: seroconversion (1), concurrent infection (12), delay in either antenatal HIV testing, or acting on result (8), no antenatal antiretroviral treatment (9), <2 weeks antiretrovirals (6), delivery viral load >10,000 (14), gestation <35 weeks (9). Also in several cases the investigators identified failure in communication between staff and mothers.
They mention one mother who transmitted who had an undetectable viral load close to delivery but had malaria in pregnancy, and her infant was PCR positive at birth.
They also noted that more than half the mothers were known to have serious immigration or housing problems.
Of the undiagnosed group (n=54), over one third of the mothers of these children had declined HIV testing in pregnancy. The investigators found that at least 20% of the mothers had tested negative in pregnancy. Often the timing of the mothers’ seroconversion was unclear. They suggest that in some cases this may have occurred after delivery and transmission to the infant through breast-feeding, which was frequently prolonged.
At presentation 57% of children had AIDS, and another 17% HIV symptoms. Diagnosis followed that of a family member for 31% of the children (most frequently the mother). Ages varied: 40 children were diagnosed at <12 months, 6 in their 2nd year and 8 in their 3rd. 11/87 children included in the audit are known to have died: 2/33 in the diagnosed group, and 9/54 in the undiagnosed group. Also, 1/35 infants born 2002-2005 and diagnosed after the audit period had died by the end of June 2008.
The investigators suggested strategies that could further reduce transmission:
- Facilitating antenatal diagnosis at any appropriate time in pregnancy.
- Identifying seroconversion in pregnancy.
- Improving staff communication.
- Closer attention to known risk factors (concurrent infection, poor response to ART, anticipating preterm delivery).
- Effective support for all infected pregnant women.
They wrote: “A review of national antenatal screening guidelines is underway. Recommendations from the audit are being fed into this review, which will consider further measures to reduce the number of infected women remaining undiagnosed at delivery, maximise antenatal test uptake, identify seroconversions in pregnancy, and improve the overall management of diagnosed women.”
Reasons for perinatal HIV transmissions in England, 2002-2005 Tookey P, Masters J, Vaughan I et al. 17th International AIDS Conference. Mexico 2008. Abstract THPE0248.