Prediction of vaginal bleeding and premature birth by ultrasound-measured cervical length in pregnant women with placenta previa

Abstract

Objective To measure the cervical length of pregnant women with placenta previa using ultrasound, and to explore the association between cervical length and premature birth or vaginal bleeding. Methods Between January 2005 and January 2010, 82 pregnant women with placenta previa who underwent prenatal examinations and delivery in our hospital were divided into three groups based on gestation weeks 28-30, 31-33 and 34-36. Ultrasound was used to measure the cervical length of pregnant women in three groups. The number of pregnant women with cervical length ＞30 mm or ≤ 30 mm was recorded. Data about vaginal bleeding, abdominal pain, symptomatic uterine contraction, pretmature birth, mean gestation age at delivery, birth weight and neonatal asphyxia rate between pregnant women with cervical length ＞30 mm or ≤30 mm in 3 groups were compared. The ROC curves of vaginal bleeding and premature delivery predicted by cervical length were generated. Area under curve (AUC) and critical point on the ROC were calculated. Results The number of pregnant women with cervical length ＞30 mm or ≤30 mm in three groups were 20, 8 of 28-30 weeks group, 19, 11 of 31-33 weeks group, 11, 13 of 34-36 weeks group respectively. Women with cervical length ≤30 mm were more likely to have vaginal bleeding, premature birth [28-30 weeks group: 87.5％ vs 20％ for vaginal bleeding, 75％ vs 15％ for premature birth; 31-33weeks group: 72.73％ vs 26.32％ for vaginal bleeding, 63.64％ vs 21.05％ for premature birth; 34-36 weeks group: 69.23％ vs 27.27％ for vaginal bleeding, 38.46％ vs 18.18％ for premature birth; all P＜0.05]. The ratio of abdominal pain and symptomatic uterine contraction in pregnant women with cervical length ≤30 mm as compared to those with cervical length ＞30 mm. The mean gestation age and birth weight were lower in pregnant women with cervical length ≤ 30 mm than those in women with cervical length ＞30 mm among three groups (all P＜0.05). In 28-30 and 31-33 weeks groups, the rates of neonatal asphyxia appeared higher in pregnant women with cervical length ≤30 mum as compared to those with cervical length ＞30 mum (all P＜0.05). No neonatal asphyxia was found in 34-36 weeks group. The AUC for vaginal bleeding and premature delivery predicted by cervical length were 73.4％ and 65.3％, with 30.5 mm being the critical point for prediction. Conclusion Measurement of cervical length by using ultrasound can be considered as a method to predict premature birth and vaginal bleeding in pregnant women with placenta previa. Key words: Placenta previa; Cervical length; Vaginal bleeding; Premature birth; Prediction