Ultrasound surveillance following cervical surgery and the risk of preterm delivery (PTD)

Abstract

This was a prospective observational study of 133 women who had previous cervical surgery attending prematurity clinics undergoing serial transvaginal ultrasonography of cervical length (CL). The CL at 16, 20 and 24 weeks’ gestation, cervical cerclage details, type of surgery and pregnancy outcome were noted. Fourteen women had either elective cerclage at 12 weeks or a preconception suture. Nineteen women developed ultrasound criteria for cerclage. Mean gestation at delivery was 257 days. Rates of PTD < 24,< 30,< 32 and < 37 weeks were 5%, 10%, 12% and 36%, respectively. Fifty-nine primigravidae were identified who had only cervical surgery as a risk factor for PTD, five women underwent US indicated and one had rescue cerclage. In this group, the PTD rates were higher than expected (9% and 20% for delivery at < 32 and < 37 weeks). A comparison of the CL of all 133 women who delivered before and after 30 weeks was made. Cervical lengths at 16, 20 and 24 weeks were all shorter in the preterm group (P = 0.002, P = 0.0043 P = 0.001) with mean differences in length of 10, 11 and 7 mm. respectively. All women with a CL of 15 mm or less at 16 weeks delivered prior to 30 weeks even with intervention. In this cohort of patients, the best negative predictive values (NPV) were with CL > 25 mm (20 weeks NPV=97% of delivery < 30 weeks, specificity=92%, sensitivity=72%).