Atosiban – A Specific Evolution for the Management of Preterm Labour

Risk factors. The presence of ‘risk factors’ in the woman’s history could theoretically be used to select a group of women for treatment.. Probably the most efficient risk factor known is a previous preterm birth, which is associated with about a three-fold increase in the risk of a further preterm delivery1. However, this only raises the risk to about 30% and is not applicable to nulliparae. In women in their first pregnancies, a low body mass index is one of the better predictors1,2 but the relative risk is only about 2 in women with spontaneous ovulation (the preterm delivery rate is up to 50% in underweight women who require ovulation induction to conceive2, but this is a very small group). Other risk factors such as minority ethnic origin, poor socio-economic status, and working during pregnancy have a significant association with preterm labour, but the relative risk is only about 1.5. There have been many attempts to combine the various risk factors into a ‘risk score’, but they fail to identify even half the women who actually deliver preterm. Predictive techniques. In continental Europe, regular digital cervical examination has been a popular approach to detecting women at high risk of preterm labour. However, a recent prospective randomised trial of 5602 women failed to show either an increase in applied interventions to prevent preterm labour, or a reduction in the preterm delivery rate3. Ultrasound examination of the cervix has suggested that with cervical lengths less than the 10% percentile (2.5cm) at 24 and 28 weeks, the relative risk of preterm birth is increased4. The presence of funnelling, which was 5.9% and 8.6% at 24 and 28 weeks respectively, was also a risk factor for preterm birth. Active measures to produce ‘funnelling’ as a test of cervical competence have also been described5; 5; 6; however, evidence of the value of the technique is currently weak. Monitoring of uterine activity, for example with home tocographs, has not proved to be efficacious7-11. The finding of fetal fibronectin in vaginal secretions is associated with a substantial risk of preterm labour12-17. However, even sampling at regular two weekly intervals was found in some studies to be too non-specific for reliable prediction18. Fibronectin screening alone has yet to be shown to have any impact on the preterm delivery rate, perhaps because of the perennial problem, lack of an effective intervention19. Currently, screening for bacterial vaginosis is undergoing a similar evaluation20-22.