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

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.