Dynamic cervical length changes: preliminary observations from 30-minute transvaginal ultrasound recordings.

OBJECTIVE

The purpose of this study was to visualize and quantify dynamic changes in the cervix and to study factors influencing cervical length.

METHODS

Eighteen women with a gestational age between 23 and 40 weeks were examined by transvaginal ultrasound during a continuous observation period of 30 minutes.

RESULTS

All women delivered at >34 weeks of gestation, fourteen at term. The overall mean difference between the shortest and longest cervical length during the 30-minute recordings (cervical length variation) was 10.9 mm (range 1.6-26.7 mm). In the presence of fetal movements directed at the cervix, peristaltic movement of the bowel or contractions, cervical length variation was larger than in the absence of these conditions (mean 12.7 mm, range 5.2-26.7 mm and mean 6.1 mm, range 1.6-9.4 mm, respectively; p = 0.03).

CONCLUSIONS

Dynamic changes in cervical length are present at early gestation and long before delivery and can be observed either spontaneously or associated with contractions, fetal movements or peristalsis. These conditions must be considered as pitfalls in cervical length measurement. In critical cases, such as early threatened preterm labor, increases in the frequency and duration of sonographic ultrasound measurements may be helpful to obtain a more reliable estimation of the cervical status.