Decline in late preterm delivery with vaginal birth in Europe

Late preterm deliveries have decreased in Europe since guidelines recommending vaginal delivery were published.

Claire Thorne showed findings from the European Collaborative Study (ECS) in EuroCoord and the Swiss Mother & Child HIV Cohort Study (MoCHiV) conducted to explore the effect of updated national guidelines in Europe on rates of late preterm delivery (defined as 34 to 36 completed gestational weeks) in HIV-positive women delivering between 2000 and 2010.

National guidance recommending vaginal delivery for women with undetectable or very low viral load, changed in Europe between 1999 and 2010. BHIVA guidelines changed in 2008.

Data conflict on the association between maternal HIV, preterm delivery and ART. The majority of preterm infants are born at 34 to 36 weeks gestation ie late preterm. In the general population, around 30% to 35% of preterm births are due to maternal or foetal indications, with induced labour or elective caesarean section. Compared to infants born full term, late preterm infants are physiologically and developmentally immature with higher rates of mortality and morbidity.

The study was a pooled analysis of data from eligible HIV positive women enrolled in the two European cohorts with a live birth between 2000 and 2010. Deliveries were stratified pre- or post- publication of national guideline change and preterm delivery rates were calculated.

Overall, 2663 mothers and 3013 deliveries were included from 10 countries; 80% (2402) delivered before and 611 20% (611) after the guidelines changed.

The women were 43% white and 48% black with a median age of 32 years (IQR 27-360) at the time of delivery. The majority (72%) were diagnosed with HIV before they became pregnant.

Overall, 76% of women received ART with 24% on ART at conception and the remainder receiving it in the first or second trimesters. Mono or dual ARV prophylaxis was used by 11%, 4% received ARVs but the strategy was unknown and 9% received nothing.

Comparing the pre-guideline with post-guideline groups: ART use increased from 72% to 90%; the proportion of women receiving no ARVs declined from 10% to 4% and mono/dual therapy decreased from 13% to 2%. The proportion of vaginal deliveries increased from 25% to 52% and elective caesarean section rates decreased from 65% to 27%. The overall rate of preterm delivery decreased from 22.8% to 12.5%. The investigators observed a decrease of late preterm deliveries from 16% to 7% after the change of guidelines, p=0.05.

Dr Thorne explained that prior to guideline changes, nearly three-fifths of late preterm deliveries were delivered by elective caesarean section, the majority with maternal HIV as the indication. Concerns about potential preterm delivery led to iatrogenic preterm delivery with elective caesarean section to avoid intrapartum risk with labour/rupture of membranes. Change in mode of delivery policy led to reduction in this strategy and in turn a decrease in proportion of late preterm infants.

It is to be expected that late preterm delivery rates in HIV positive women will continue to decline as increasing proportions of women with undetectable viral load deliver vaginally.

Aebi-Popp K et al. Vaginal delivery as option for HIV infected women: decreasing late preterm delivery rates in a European cohort collaboration. 5th International Workshop on HIV Pediatrics. 28 – 29 June 2013, Kuala Lumpur, Malaysia. Late breaker oral abstract. O_14.
http://regist2.virology-education.com/2013/5hivped/docs/25_Thorne.pdf