Cervical length at 23 weeks' gestation - relation to demographic characteristics and previous obstetric history in South African women

Objectives. To determine the distribution of cervical length in a routine population of singleton pregnancies; to examine the relationship between cervical length, demographic characteristics, and previous obstetric history; and to compare these data with data from a similar study undertaken in the UK. Patients and methods. The study was conducted among women attending routine antenatal clinics at Coronation, Johannesburg General and Chris Hani Baragwanath hospitals. Cervical length was measured by means of transvaginal ultrasound at 23 weeks' gestation in women with singleton pregnancies attending these clinics, as part of a multicentre randomised trial investigating the value of cerclage in a short cervix. The distribution of cervical length was determined and the significance of differences in median cervical lengths between subgroups was calculated according to maternal age, ethnic origin, maternal body mass index (BMI), cigarette smoking, alcohol intake, and previous obstetric history. Results. Cervical screening was offered to women (N = 2 173) attending clinics for a 23-week scan during the study period (July 1999 - September 2002). Most women (N = 1920) accepted, while 253 declined. Complete outcomes (date and mode of delivery, gestation at delivery, birth weight, Apgar scores, maternal blood loss, whether the patient was cerclaged or not, and any complications) were obtained for 1603 women who accepted screening. Cervical length was measured successfully in all cases. Median cervical length was 33.7 mm and in 64 cases (3.3%) the length was 15 mm or less. Significantly shorter cervical lengths were found in those with a history of previous miscarriage, preterm delivery, those aged less than 20 years and those with an abnormal BMI. Cervical length was not significantly shorter in black women than in coloured and white women. Conclusions. At 23 weeks' gestation the median cervical length in a South African population was 33.2 nun. In 3.3% of the population the length was <= 15 mm. There was an association between cervical length, demographic characteristics and previous obstetric history.