BACKGROUND Labour is the process of parturition that involves the uterus and cervix with the resultant effect of expulsion of the products of conception out of the uterus through the vagina after the age of viability. The cervix plays a key role in this process as the shortening of cervical length and associated dilatation is necessary for the final expulsion of product of conception. Pregnancy is defined to be term when it is between 37 completed weeks and 41 weeks 6 days. The exact date of onset of labour is difficult to predict even in same person with different pregnancies as it varies from race to race and even in same individual. The usefulness of cervical length assessment in the mid trimester in diagnosing pregnancies with a high-risk of spontaneous preterm labour has been confirmed by various studies. The value of the same cervical length assessment at term in predicting the onset of spontaneous labour is being debated. These studies are also not available in this environment. AIM The aim of this study is to establish a relationship between sonographic cervical length measurement at term and the timing of onset of spontaneous labour. DESIGN This was a prospective longitudinal study, carried out on 124 pregnant women who attended antenatal clinic at Olabisi Onabanjo University Teaching Hospital, Sagamu. They were recruited consecutively from the antenatal clinic till sample size was completed. Transvaginal ultrasound measurement of the cervical length was done weekly from 37 weeks gestation age till 41weeks. Information on onset of labour was retrieved from respondents’ case files and recorded on a data capture sheet. Data was analysed using the IBM SPSS Statistics 22(Armonk, NY: IBM Corp).