ABC of preterm birth: Obstetric issues in preterm birth
Predicting and preventing preterm labour and choosing the safest method of delivery are important challenges in reducing the number of preterm births and improving outcomes for mother and baby. This article covers the predictive tests, methods of prevention, maternal and fetal indications for preterm birth, and various approaches to delivery.
Most preterm deliveries follow spontaneous onset of preterm labour or preterm prelabour rupture of the amniotic membranes (pPROM). Much work has been done (with limited success) to find diagnostic tests that predict accurately if a woman who is at risk of preterm delivery will go on to deliver preterm. For these women, who may have a history of preterm birth or clinical signs of preterm labour, such tests would allow early and targeted use of antenatal interventions. These interventions, especially antenatal corticosteroids, improve neonatal and long term outcomes for preterm infants.
The most common clinical tests used to determine the risk of preterm labour are transvaginal sonography (to measure the length of the endocervix) and the cervicovaginal fetal fibronectin test. These tests have high negative predictive values - that is, if results are negative then the women probably will not progress to preterm delivery. Although there does not seem to