Universal Cervical Length Screening for Prediction and Prevention of Preterm Birth

Universal transvaginal ultrasound (TVU) cervical length (CL) screening represent a step forward in the campaign against preterm birth (PTB). Transvaginal ultrasound CL is a safe, acceptable, reproducible, and accurate screening test, with potentially widespread availability given its feasibility. For this screening to be effective, the ultrasounds should be done with proper TVU technique and with continuing quality assurance. Clinicians should refrain from screening different populations, at different gestational ages, and from stretching the definition of short CL to include measurements above 25 mm. A single TVU CL measurement at about 18 to 24 6/7 weeks can be offered to all singleton gestations. About 2% to 5% of these women will demonstrate a TVU CL of 20 mm or less and should be offered vaginal progesterone, either 200-mg suppository or 90-mg gel daily, until 36 weeks, being counseled that this intervention has been associated with about 45% decrease in PTB and neonatal benefits. Serial TVU CL measurements, about every 2 weeks and weekly if CL is 25 to 29 mm, can be offered between about 16 and 23 6/7 weeks to singleton gestations with a prior spontaneous PTB. In the 40% of these women who will develop a short TVU CL of less than 25 mm, cerclage should be offered, as it is associated with a significant 30% reduction in the risk of PTB less than 35 weeks and a 36% reduction in composite perinatal mortality and morbidity. Transabdominal CL screening has not been sufficiently studied and cannot be recommended. Results from just 1 trial offer promise for pessary as another effective intervention, which cannot be recommended yet until results are confirmed with another trial. Transvaginal ultrasound CL in multiples cannot be recommended yet, given lack of effective interventions in this population. Target Audience: Obstetricians and gynecologists, family physicians. Learning Objectives: After completing this CME activity, physicians should be better able to evaluate the effectiveness of using transvaginal ultrasound as a screening test to measure cervical length; evaluate the effectiveness of various interventions for prevention of preterm birth in women with short cervical length; use an algorithm to determine the clinical use of cervical length screening in women with, and in women without, prior preterm birth; and evaluate the effectiveness of vaginal progesterone for prevention of preterm birth in women with short cervical length.