1. TRANSVAGINAL CERVICAL LENGTH AND MODIFIED BISHOP SCORE IN PREDICTION OF SUCCESSFUL LABOUR INDUCTION IN POSTDATE PREGNANCIES
Soe Kyaw Kyaw, Ei Shwe Syn, San San Myint
Department of Obstetrics and Gynaecology
University of Medicine 1, Yangon

2. Introduction Post-date pregnancy Cochrane (2012)1 Common situation
Associated with increased perinatal morbidity and mortality
Cochrane (2012)1
routine induction of labour at 41 or more weeks’ gestation reduces perinatal mortality without increasing the overall risk of caesarean section or operative delivery to the mother
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3. Introduction (contd) Outcome of induction of labour
less than two thirds of women gave birth without further intervention
about 15% having instrumental births
22% having emergency caesarean sections
Influenced by state of cervix at the beginning of induction
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4. Introduction (contd)
Conventionally, cervical status is assessed by modified Bishop score
Bishop score have intra and interpersonal variation.
Transvaginal ultrasound for cervical length measurement was found to be less painful and more objective than modified Bishop Score.
A cervical length of more than 20 mm in labour induction at term is an independent predictor of caesarean delivery. (Tan et al, 2007)2
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5. Aim
To study the transvaginal cervical length and modified Bishop score in the prediction of successful labour induction in post-date pregnancies
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6. Method Hospital based prospective comparative study
Conducted in CWH, Yangon from 1st January 2016 to 31st December 2016
Total 106 women with post-date pregnancies were recruited according to inclusion criteria
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7. Method (contd) Inclusion Criteria
Singleton pregnancy between 40 weeks and 40+10weeks
Live fetus in cephalic presentation
Intact membranes
Women with gravida up to 4
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8. Method (contd) Exclusion Criteria Grandmultiparity
Antepartum hemorrhage
Previous cervical surgery
Previous uterine surgery (myomectomy or previous caesarean section)
Dilatation of cervix greater than 3 cm
Foetal malpresentation
Women with any contraindication to vaginal delivery
Women with contraindication to prostaglandin (e.g. allergy, bronchial asthma, hypotension, palpitation)
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10. Results
Correlation of Mean Cervical Length by TVS and Modified Bishop Score with the Vaginal Delivery and Caesarean Section Groups
Variables
Vaginal delivery (n=60)
Caesarean section (n=46)
t statistics
P value
Mean cervical length (mm) + SD
.047
0.001
Mean modified Bishop score + SD
5.273
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11. Results (contd)
Comparison of Modified Bishop Score and Transvaginal Sonography for Cervical Length for Predicting Successful Induction of Labour in Post-date Pregnancies
Variables
RR (95% CI)
P value
Sensitivity (%)
Specificity (%)
PPV (%)
NPV (%)
Cervical length (> 25 mm vs. <25 mm)
3.31 (2.0 – 5.47)
AUC – 79.1
<0.001
80.0
78.3
82.7 75
Bishop score (<6 vs. >6)
2.53 (1.77– 3.6)
AUC – 76.2
63.3
89.1
88.3
65.1
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12. Discussion
The cervical length by transvaginal ultrasound had significant correlation with the outcome of induction of labour.
The shorter the cervical length, the greater was the chance of successful induction of labour.
In this study, the mean cervical length for women with vaginal delivery was mm and that for caesarean section was mm. (P = 0.001)
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13. Discussion (contd) Mean CL for vaginal delivery
Mean CL for caesarean delivery
P value
Pereira et al3
19.6 mm
23 mm
0.049
Uzun et al4
25.88 mm
33.03 mm
0.0001
Tan et al2
21.7 mm
24.7 mm
0.024
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14. Discussion (contd)
For modified Bishop score, it was already accepted that the greater the score, the higher the rate of successful induction of labour.
In this study, the mean Bishop score for women with vaginal delivery was 5.5 and that for those with caesarean section was (P=0.001)
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15. Discussion (contd) Mean Bishop score for vaginal delivery
Mean Bishop score for caesarean delivery
P value
Pereira et al3 5 4
0.037
Uzun et al4
6.17
2.39
0.0001
Tan et al 2
5.8
5.1
0.021
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16. Discussion (contd)
In this study, the cervical length by TVS of less than 25 mm had the relative risk of 3.31 (95% CI 2.0 – 5.47, P <0.001) for vaginal delivery, compared with the cervical length of 25 mm and above. (Sensitivity = 80%, Specificity = 78.3%, PPV = 82.7%, NPV = 75%)
The modified Bishop score 6 and above was shown to have 2.53 times chance (95% CI 1.77 – 3.6, P <0.001) for vaginal delivery after induction of labour when compared with the score of less than 6. (Sensitivity = 63.3%, Specificity = 89.1%, PPV = 88.3%, NPV = 65.1%)
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17. Discussion (contd) Tan et al (2007)2
the best cut-off of cervical length for caesarean section after induction was more than 20 mm (sensitivity 80%, specificity 47%, positive predictive value 30%, negative predictive value of 89%)
Cut-off Bishop score for caesarean section after induction of labour was 5 or less (sensitivity = 64%, specificity = 51%, positive predictive value = 30%, negative predictive value = 83%)
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18. Discussion (contd) Elghorori et al (2006)5
optimal cut-off for cervical length for prediction of successful induction was 34 mm and below
the sensitivity of 62% and specificity of 100%
optimal cut-off value of Bishop score was more than 5
the sensitivity of 23% and the specificity of 88%.
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19. Discussion (contd) Gonen et al (1998)6
the threshold for cervical length for the best predictor of successful induction was 27 mm (sensitivity = 59%, specificity = 78%, positive predictive value = 82%, negative predictive value = 53%)
Bishop score of 6 and above had sensitivity of 65%, specificity of 78%, positive predictive value of 83% and negative predictive value of 57% for successful induction of labour.
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20. Conclusion
The cervical length measurement by TVS had greater sensitivity than modified Bishop score for prediction of successful induction of labour in post-date pregnancy.
It also had similar specificity, positive predictive value and negative predictive value to modified Bishop score.
The predictive value of modified Bishop score for successful induction can probably be improved if it is combined with cervical length by TVS.
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21. Reference
1. Gulmezoglu AM, Crowther CA, Middleton P, Heathey E (2012). Induction of labour for improving birth outcomes for women at or beyond term. The Cochrane Collaboration. 2. Tan PC, Vallikkannu N, Suguna S, Quek KF and Hassan J (2007). Transvaginal sonographic measurement of cervical length vs. Bishop score in labour induction at term: tolerability and prediction of Caesarean delivery. Ultrasound in Obstetrics and Gynaecology; 29: Pereira S, Frick AP, Poon LC, Zamprakou A and Nicolaides KH (2014). Successful induction of labour: prediction by preinduction cervical length, angle of progression and cervical elastography. Ultrasound in Obstetrics and Gynaecology; 44: Uzun I, Sik A, Sevket O, Aygun M, Karahasanoglu A and Yazicioglu HF (2013). Bishop score versus ultrasound of ther cervix before induction of labour for prolonged pregnancy: which one is better for prediction of Caesarean delivery. The Journal of Maternal-Foetal and Neonatal Medicine; 26(14): Elghorori MR, Hassan I, Dartey W and Abdel-Aziz E (2006). A way to lend objectivity to Bishop score. Journal of Obstetrics and Gynaecology; 26(4): Gonen R, Degani S and Ron A (1998). Prediction of successful induction of labour: comparison of transvaginal ultrasonography and the Bishop score. European Journal of Ultrasound;7:
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