Objective To construct normograms for cervical length in low-risk, singleton pregnancies from 14 weeks to 40 weeks gestation.

Study design This was a prospective, cross-sectional study involving low-risk women attending Cork University Maternity Hospital conducted concurrently with a primary study to construct normograms for fetal biometry. Women were recruited in the first trimester and randomly allocated to a single scan between 14–40 weeks gestation. Scans were performed by a sole researcher. Gestation was calculated using the estimated due date assigned by dating scan. Recruits were Irish Caucasian women with a singleton pregnancy. Women with a previous history of preterm labour, mid-trimester pregnancy loss, cervical sutures, cone biopsy and large loop excision of transformation zone (LLETZ) were excluded. Measurements were obtained transvaginally using the Voluson E8 ultrasound by GE Healthcare.

Results Seven-hundred-and-ninety-three women were recruited into the primary study. Five-hundred-and-fifty-five women consented to cervical length measurements and were scanned as per protocol. Median maternal age was 32 (range 17–44). Median BMI was 24.7 (range 17.1–48.6). Nulliparous women constituted 46.5% (369/793) of recruits, 32.6% (261/793) were expecting their second child, 18.3% (145/793) were expecting their third or fourth child, while only 2.3% (18/793) were grand multiparous. Normograms for cervical length have been generated for this population. The following table demonstrates the calculated percentiles for each gestational week.

Conclusion We have constructed normograms for cervical length from 14 to 40 weeks gestation in the low-risk Irish Caucasian population.