Objective:  To evaluate the impact of cervical length (CL) measurements in pregnant women at risk for preterm delivery on intervention and pregnancy outcome.

Design:  Retrospective study.

Setting:  Regional high-level II maternity unit.

Methods:  Hospital databases were reviewed for all women delivering between March 2001 and March 2003. Women at an increased risk for preterm birth with transvaginal (TV) cervical length measurements during pregnancy were included in this audit. Patients (n = 204) were analysed together and in subgroups with different risk profiles.

Results:  For women with a significant obstetrical history, most of the cervical lengths ≤ 2.5 cm were found between 24 and 28 weeks gestational age. None of the patients with twin pregnancy as single indication for cervical length measurements developed a cervical length ≤ 2.5 cm. In women with twin pregnancy plus additional risk factor as indication for cervical length measurement, 60.87% showed shortening of cervical length to ≤ 2.5 cm. Patients with previous gynaecological operations as the only risk factor had optimal perinatal outcomes. Notwithstanding the potential beneficial effects of therapeutic measures, patients with singleton pregnancies and a significant obstetrical history, and a short cervical length had a relative risk of 3 for preterm delivery. In the group of women presenting with signs and symptoms suggestive of threatening preterm delivery and a short cervical length, significantly more patients were treated with nifedipine compared to similar patients with ‘normal’ cervical length.

Conclusions:  For patients with a high-risk obstetrical history, a first cervical length measurement at the time of foetal morphology scan followed by one measurement at about 24 weeks would result in a timely diagnosis of almost all cases of clinically relevant cervical shortening. Just having a twin pregnancy, in the absence of other risk factors for preterm birth, does not require cervical length monitoring. Having a twin pregnancy plus additional risk factors clearly identifies a group requiring cervical length measurement and intervention. Previous LLETZ procedures or ≥ 3 preceding curettages were not found to be a major risk factor for preterm birth.