| In clinical obstetrics and gynecology , cervical ripeness is the key to correctly evaluate the situation for cervical ripening and estimate the tme to beginning of labor for the "timely labor induction" , or to choose the mode of delivery rightly for reducing the rate of cesarean section and raising the rate of the successful induction . Cervical Bishop score system has been applied by obstetricians to estimate the cervical ripeness and to determine whether the nulliparous women should have labor induction ,but because the method is subjective, it has great impact on estimating the time to beginning of labor and the cervical ripening. We can observe the cervical morphology and quantify the morphologic parameters of cervix objectively by ultrasound. This method has been applied to the diagnosis and treatment of cervical incompetence and premature predictions. In view of the transperineal sonography will be able to measure the morphologic parameters of cervix objectively and accurately,we observe the changes of cervical morphology among nulliparous women using transperineal sonography and to analyze the relationship between the morphologic parameters of cervix and the time to beginning of labor.We hope to find a simple, effective method on predicting the onset time of term labor.Objective: To observe the cervical morphology among nulliparous women using transperineal sonography and quantify the morphologic parameters of cervix to analyze the relationship between the morphologic parameters of cervix and the time to beginning of labor ,then to determine their predictive value on the mode of delivery.Methods: We use GE 730 color Doppler ultrasonic machine(3.5 MHz) to observe the cervical morphology by transperineal sonography among 85 nulliparous pregnant women who have examination in the department of obstetrics and gynecology in our hospital.The method: After emptying bladder , pregnant women keep lithotomy position.Scan between greater lip of pudendum by convex array probe, in the sagittal plane of cervix ,take the measurement of cervical length,the anteroposterior diameter of cervix,the diameter of cervical canal,the internal os, in the cross-sectional plane, measure the cervical width, the external os. Measure each data for three times and take the average.Record the time to beginning of labor,the mode of delivery, the time of vaginal delivery labor, indications of cesarean section.Results: In this study, the average maternity gestation age: 40.14±0.87 week. The rate of cesarean section was 36.5% (31/85).There was a 100% success rate for transperineal sonography by observing 85 cervix in pregnancy. The average of cervical length: 25.91±5.62 (mm), the average of the anteroposterior diameter of cervix :31.32±7.51 (mm), the average of Cervical width: 38.82±10.28 (mm), the average of the diameter of cervical canal :3.46±0.06 (mm), the average of the internal os:2.83±0.35 (mm), the average of the external os :7.33±1.0 (mm).1 The relationship between morphologic parameters of cervix and gestation age1.1 Observe the cervical length of 85 pregnant women in different gestation age.With the increasing of the gestation age, the cervical length became shorter than before .There was a significant correlation between gestation age(GA) and cervical length(CL).The regressive formulas :CL (mm)= 166.812-3.617×GA (week) (r =- 0.522, P <0.001).1.2 With the increasing of the gestation age, the diameter of cervical canal is gradually increasing. The diameter of cervical canal in different gestation age had a significant difference (P <0.0001).There was a significant correlation between gestation age(GA) and the diameter of cervical canal .The regressive formulas : the diameter of cervical canal (mm) = 0.358×GA (week) -10.5 (r = 0.486, P <0.001).1.3 With the increasing of the gestation age,the anteroposterior diameter of cervix decreased, but the difference was not statistically significant (P> 0.05).2 The relationship between morphologic parameters of cervix and the time to beginning of laborMultiple linear regression analysis identified cervical length, cervical width and the diameter of cervical canal were significantly related to the time to beginning of labor, the regressive formulas: the time to beginning of labor (week) = 0.506×cervical length(mm) -0.199×the diameter of cervical canal(mm) +0.232×cervical width (mm) (r = 0.616, P <0.0001).3 The predictive value of morphologic parameters of cervix on the time to beginning of labor within 7 days3.1 The groups were divided by the time to beginning of labor: within 1 week(A) or >1 week(B)3.1.1 The cervical length of group A is shorter than that of group B, the difference of cervical length between the two groups is statistically significant (P <0.0001).3.1.2 The cervical width of group B is wider than that of group A. the difference of Cervical width between the two groups is statistically significant (P <0.0001).3.1.3 The diameter of cervical canal of group A is wider than that of group B ,the difference of the diameter of cervical canal between the two groups is statistically significant (P <0.0001).3.2 Multivariate logistic regression analysis identified cervical length, cervical width and the diameter of cervical canal were significantly related to the time to beginning of labor within 7 days. the regressive formulas: prediction of the time to beginning of labor within 7 days = 0.317×cervical length +0.101×cervical width -1.310×the diameter of cervical canal (P <0.05).3.3 The ROC curves for transperineal sonographically measured morphologic parameters of cervix for predicting the time to beginning of labor within 7 days indicated that cervical length, cervical width and the diameter of cervical canal have a better predictive value.Cervical length was 23 mm, sensitivity: 0.881 specificity: 0.649.Cervical width was 40 mm, sensitivity: 0.667 specificity: 0.595. The diameter of cervical canal was 3.05mm, sensitivity: 0.919,specificity: 0.524. (P <0.0001)4 The relationship between morphologic parameters of cervix and the mode of deliveryMultivariate logistic regression analysis identified that morphologic parameters of cervix were not significantly related to the mode of delivery(P>0.05).The difference of cervical length between the cesarean delivery group and vaginal delivery group is not statistically significant (P> 0.05).5 The relationship between morphologic parameters of cervix and the time of laborMultivariate logistic regression analysis identified that morphologic parameters of cervix were not significantly related to the time of labor(P>0.05 )Conclusion:Transperineal sonography can show the cervix clearly.1 The results of this study indicate that with increasing gestation age ,cervical length and the diameter of cervical canal changed too. The cervical length became shorter than before,the diameter of cervical canal is gradually increasing. there was a significant correlation between gestation age(GA) and cervical length,the diameter of cervical canal。2 The time to beginning of labor were significantly related to cervical length, cervical width and the diameter of cervical canal. the regressive formulas: the time to beginning of labor (week) = 0.506×cervical length(mm) -0.199×the diameter of cervical canal(mm)+0.232×cervical width (mm) (r=0.616,P <0.0001),we can estimate the time to beginning of labor by the regressive formulas.3 From the ROC curves we know that cervical length, cervical width and the diameter of cervical canal have a better predictive value in predicting the time to beginning of labor within 7 days: cervical length was 23 mm, sensitivity: 0.881 specificity: 0.649;cervical width was 40 mm, sensitivity: 0.667 specificity: 0.595;the diameter of cervical canal was 3.05mm, sensitivity: 0.919,specificity: 0.524. The cervical length have the highest diagnostic specificity of forecast the time to beginning of labor within 7 days . in Actual Clinical work , we can considered the cervical length, width and the diameter of cervical canal together to predicte the possibility of the onset time of labor within 1 week.In conclusion,avoiding the subjectivity of the traditional Bishop score, transperineal sonography is a simple convenient, safe and practical method and have realistic value in clinical work of obstetrics and gynecology.
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