Consecutive measurement of cervical length during uncomplicated pregnancy through transvaginal ultrasound

Objective To investigate the change of cervical length (CL) during uncomplicated pregnancy by transvaginal ultrasound and its correlated factors. Methods Data of five hundred and ninety-five normal singleton pregnant women who received vaginal ultrasound examination on CL in their 11-13+6gestational weeks ( Ⅰ stage),20-24 gestational weeks ( Ⅱ stage),28-32 gestational weeks (Ⅲ stage) and ≥36 gestational weeks (Ⅳ stage) were collected and retrospectively analyzed.Related factors were recorded at the same time.Repeated measurement data analysis of variance,t-test and Spearman correlation analysis were applied for statistical analysis. Results (1) The mean values of CL at Ⅰ,Ⅱ,Ⅲ and Ⅳ stage were (38.85±3.11) mm,(38.92±4.10) mm,(36.43±4.69) mm and (30.63±6.11) mm,respectively.There were statistical differences between the CL of any two stages (P＜0.01),except for that between Ⅰ and Ⅱ stage.The median values of CL change rates were:Ⅱ-Ⅰ stage0.00％; Ⅲ-Ⅰ stage -5.36％; Ⅳ-Ⅰ stage -20.00％.(2) The CL of pregnant women who were older than 35 was longer than that of those younger than 35 at any stage [ Ⅰ stage:(39.36±3.18) mm vs (38.77±3.10) mm;Ⅱ stage:(39.89±4.61) mm vs (38.88±4.00) mm;Ⅲ stage:(37.29±4.79) mm vs (36.31 ±4.67) mm;Ⅳ stage:(32.25± 5.95) mm vs (30.38±6.10) mm],while significant difference was found only at Ⅳ stage (t=-2.56,P=0.01).The CL of multiparas was longer than that of primiparas [ Ⅰ stage:(38.95±2.59) mm vs (38.76±3.14) mm;Ⅱ stage:(39.54±3.62) mm vs (38.82±4.11) mm;Ⅲ stage:(37.37±4.21) mm vs (36.34±4.70) mm;Ⅳ stage:(31.77±6.05) mm vs (30.59±6.11) mm],while there was no statistical significance within any stage ( P＞ 0.05). Conclusions Cervix shortens gradually after 28 gestational weeks.Sequential measurement of CL during routine ultrasonic inspection might be helpful in predicting preterm labor. Key words: Pregnancy; Cervical length measurement; Ultrasonography,prenatal