Sonographic cervical length in threatened preterm labor in a South African population

In a previous study conducted in the UK we demonstrated that only 8% of women with threatened preterm labor deliver within 7 days. Furthermore, delivery within 7 days occurred in less than 1% of women presenting with a sonographically measured cervical length > or = 15 mm, compared to 37% in those with cervical length < 15 mm. In this study we investigate the potential value of cervical length in the prediction of outcome of threatened preterm labor in a South African population.

We examined 63 women with singleton pregnancies presenting with regular and painful uterine contractions at 24-36 (mean, 31) weeks of gestation. Women in active labor, defined by the presence of cervical dilatation > or = 3 cm, and those with ruptured membranes were excluded. On admission to the hospital a transvaginal scan was performed to measure the cervical length. The subsequent management was determined by the attending obstetrician. The primary outcome was delivery within 7 days of presentation.

Delivery within 7 days of presentation occurred in 20/63 (32%) pregnancies, including 20 of the 30 (67%) cases with cervical length < 15 mm and none of the 33 cases with cervical length > or = 15 mm. Logistic regression analysis demonstrated that the only significant contributor in the prediction of delivery within 7 days was cervical length (odds ratio 0.67; 95% CI 0.54-0.85; P = 0.001) with no significant independent contribution from maternal age, gestational age, body mass index, parity, use of antibiotics, previous history of preterm delivery, cigarette smoking, contraction frequency or use of tocolytics.

In this South African population, which had a high incidence of delivery within 7 days of presentation with threatened preterm labor, sonographic measurement of cervical length is equally effective as in a lower-risk population in distinguishing between true and false labor.