Preterm labour is the onset of regular uterine contractions associated with progressive cervical change between viability and 37 completed weeks of gestation. The incidence is between 5% and 10% in most developed nations. In the US, the incidence has increased from 9% to 12% in the past two decades. Preterm delivery can be associated with immediate and long-term neonatal complications. Long-term morbidity includes cerebral palsy, neurodevelopmental delay and chronic lung disease. The neonatal outcome is dependent on the gestational age at delivery and associated features such as infection. The lower the gestational age, the higher the risk of mortality and morbidity. The management of preterm labour involves identification of high-risk women, prevention and treatment.

IDENTIFICATION OF AND PREVENTION IN WOMEN AT RISK

The identification of women at high risk of preterm delivery remains a major challenge. Scoring systems based on socioeconomic status, obstetric or medical history and antenatal events in the index pregnancy have shown a suboptimal correlation with subsequent preterm birth.¹ This is primarily because the single greatest risk factor is a history of preterm labour, so delivery cannot be reliably predicted in the first pregnancy. The risk of preterm delivery after one and two previous preterm deliveries has been given as 15% and 41%, respectively¹; however, such figures are difficult to apply to individuals as the risk is dependent on the cause and the gestational age of the previous preterm delivery.

Investigations such as fetal fibronectin or cervical ultrasound can be used to identify women at high risk. A positive swab for vaginal fetal fibronectin taken in the late second or early third trimester increases the likelihood of delivery before 34 weeks by a factor of 4.² Likewise, a negative swab reduces the likelihood of delivery to 0.78. Such results from meta-analysis include women both at high risk and at low risk. …