Sonographic measurement of cervical length and its relation to the onset of spontaneous labour and the mode of delivery.

Background.: We aimed to investigate the relationship between cervical length at 37 weeks of pregnancy and the onset of spontaneous labour as well as mode of delivery.

Methods.: We did a prospective observational study of 126 low-risk pregnant women with cephalic presentation who were not in labour, attending a south Tehran health centre for prenatal care. The length of the cervix was measured using transvaginal ultrasound (10 MHz endovaginal transducer) by a single sonographer at 37 weeks of gestation. The outcomes were the onset of spontaneous labour and the mode of delivery.

Results.: The mean cervical length was 26.1 mm (range 10-51 mm), with a non-significant difference between nulliparous and parous women (p=0.36). There was a significant association between cervical length and onset of spontaneous labour (r=0.33, p<0.001). When controlled for parity, maternal height and onset of spontaneous labour, cervical length did not predict the mode of delivery (p=0.79).

Conclusion.: Measurement of cervical length at 37 weeks could predict the onset of spontaneous labour, but it failed to predict the mode of delivery.