Duration of ruptured membranes and vertical transmission in the UK

Polly Clayden, HIV i-Base

Longer duration of rupture of membranes (ROM) was identified as a risk factor for mother to child transmission (MTCT) in the 1990s. Elective caesarean section prior to ROM was found to be protective.  However, these studies were conducted before the availability of HAART.

Whether duration of ROM has clinical implications for women on effective HAART is unclear. An increasing number of women in the UK opt to deliver vaginally but, of these, a high proportion, undergo emergency caesarean section. It is likely that concern over ROM contributes to this management decision.

In an oral presentation at the 2010 BHIVA/BASHH meeting, Pat Tookey showed findings from an investigation, using routine surveillance data from UK and Ireland, to explore the association between duration of ROM and transmission. Surveillance of obstetric and paediatric HIV is conducted through the National Study of HIV in Pregnancy and Childhood (NSHPC). Data on ROM have been collected since January 2007.

In this study, the investigators reviewed pregnancies resulting in live singleton births among HIV-positive women reported in 2007-9.

During this period, 2686 births were reported. The majority (95%) of mothers were on HAART; 40% had an elective caesarean section, 34 had vaginal delivery and 26% emergency caesarean section. Almost Three quarters of mothers (74%) had an undetectable viral load and the rate of mother to child transmission was 0.9% (15/1697).

Of the total, 1063/2686 mothers had an elective caesarean and data were missing for 298. There were ROM data for 1325, of which 884 (67%) had ROM prior to delivery and data on duration was provided for 661 (75%). The median duration was 4 hrs (IQR 1.5-8), <6hrs for 444 (67%), >6-48 hrs for 217 (33%), this included 16 mother with >48 hrs ROM.

There were 6/421 (1.4%) transmissions overall, among the infants with confirmed HIV status. The rate was similar for infants with < 6 hrs ROM, 2/284 (1.4 compared to those with  >6 hours, 2/137 (1.5%), OR 1.0 (95%CI 0.2-5.7, p=1.0)

In the sub group of women with undetectable viral load (<50 copies/mL) near delivery (99.7% on HAART), there was no difference in MTCT (overall 1/341, 0.3%), between those with ROM for >6 hrs compared to <6 hrs (0/112, 0.4% vs 1/229, 0.0%, p=1.00). Likewise, among mothers with undetectable viral load who had a planned vaginal delivery (overall 1/203, 0.5%:  0/52, 0% vs 1/151, p=1.0).

Six of the 661 children had confirmed infection at the time of analysis including 3 likely in utero transmissions (positive PCR on Day 1, see Table 1).

Table 1: Six children infected with HIV who were born to women with ROM before delivery

Case 1 Case 2 Case 3 Case 4 Case 5 Case 6
ROM (hrs/mins) 12.45 4.00 3.29 5.50 6.50 4.37
Mode of delivery EMCS Vaginal EMCS EMCS EMCS Vaginal (unplanned)
Gestational age (week) 38 40 36 39 40 37
HAART   (start week) Yes (33) Yes (17) Yes (17) Yes (22) Yes (21) Yes (32)
Maternal viral load * 330 <40 48,230 71, 500 122,040 23, 460
1st positive PCR Day 1 16 weeks Day 1 6 weeks Day 4 Day 1

* closest to delivery. Note: Patients 1, 5 and 6 had reported adherence issues.

The investigators concluded that although data are sparse to date, so far there is no evidence that among women on HAART longer duration of ROM is associated with an increased risk of MTCT. Larger sample sizes are required and comprehensive data on: ROM and duration of ROM, infant infection status and viral load close to delivery. Continuing monitoring is essential.

Ref: Haile-Selassie H et al. Duration of ruptured membranes and vertical transmission of HIV: data from national surveillance in the UK and Ireland. 2nd Joint Conference of BHIVA with BASHH, 20–23 April 2010,  Manchester. Oral abstract O2.

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