Is 25 mm the correct mid-trimester cut-off for cervical shortening among asymptomatic women?

Abstract

Objectives: To evaluate the impact of asymptomatic cervical shortening (ACS) at mid-trimester on maternal and neonatal outcomes.

Methods: This was a retrospective cohort study. Women with singleton gestations and an accidental finding of cervical length of 25 mm or less at mid-trimester were compared with women with symptomatic cervical shortening (SCS) and women with normal cervical length (NCL). Primary outcome was preterm birth (PTB) rate; secondary outcomes included total hospitalization length, betamethasone treatment rate, and a composite of PTB neonatal outcomes.

Results: In all, 1483 women were diagnosed with ACS. There was no difference in early and late PTB rate between the ACS and NCL groups (4.9% versus 3.8%, P = 0.25), though there was a significantly higher rate of antenatal corticosteroids use in the ACS group (78.2% versus 7.4%, P < 0.001). A CL of 15 mm or less was significantly associated with both early and late PTB, compared with the NCL group (47.2% versus 3.6%, P < 0.001, and 35.8% versus 3.8%, P < 0.001).

Conclusions: An ACS of 15-25 mm is not associated with an increased risk of PTB. In contrast, women with a CL of 15 mm or less are more likely to delivery prematurely compared with women with a CL greater than 15 mm.

Keywords: asymptomatic; cervical length; cervical shortening; preterm birth; transvaginal sonography.