Change in cervical length in cases resulting in threatened preterm labor.

Abstract

To determine the predisposing changes in cervical length (CL) and the critical range of CL in which significant uterine contractions emerge resulting in threatened preterm labor (TPL). Sixty-eight uncomplicated singleton pregnancies where the CL was <25mm before 31weeks were divided into cases with TPL (n=23) or without (n=45). CL and uterine contractions were monitored sequentially starting between 16 and 20weeks. The gestational ages when a CL of <25 or <15mm was first observed, the interval between these two measurements, and the CL value at TPL diagnosis were analyzed retrospectively. (1) The gestational ages when a CL of <25 and <15mm was first detected were lower in the TPL group (25 (median); 18-30 (range) and 28; 25-33weeks, respectively) than in the non-TPL group (27; 20-30 and 33; 26-35weeks; P=0.030 and P<0.001). (2) The interval between the two measurements was shorter in the TPL group (2.5; 0-15weeks) than in the non-TPL group (5.5; 0-13weeks, P=0.034). (3) The CL value at TPL diagnosis was 13mm (median), ranging from 7 to 18mm. Cases with early onset and subsequent rapid CL shortening before 31weeks resulted in TPL when CL decreased below the range 7-18mm.