Associations of temporal changes in cervical length and lower uterine segment length with spontaneous preterm delivery risk: a prospective study of 727 Japanese women.

PURPOSE: A prospective assessment of the risk of spontaneous preterm delivery (sPTD) by evaluating temporal changes in cervical measurements.

METHODS: We analyzed clinical variables, focusing on cervical length (CL) and lower uterine segment (LUS) length (LUSL) as measured by transvaginal ultrasonography in 727 pregnant Japanese women.

RESULTS: In women undergoing term deliveries, CL increased from gestational week (GW) 8-25. In contrast, the combination of CL and LUSL (ComL for "combined length") gradually decreased and sole LUSL became almost 0 mm by GW 25. Univariate logistic regression analysis suggested that a history of PTD was a risk factor for sPTD. CL, LUSL, and ComL were not significant predictors of sPTD.

CONCLUSION: To assess the risk of sPTD in the second trimester, it is not necessary to distinguish the cervix from the LUS.