Modifying Cervical Bishop Scoring System

After approval of the ethical \& scientific committees of the OBGYN department of Kasr El Aini hospital, 80 primigravidas undergoing induction of labour at our hospital in a prospective blind study were subjected to history taking, examination, investigations \& ultrasonography. Indication for pregnancy termination was explained to each patient and a written consent was obtained.

Clinical examination \& assessment:

Patients were examined vaginally by the attending physician and a Bishop score was assigned and recorded according to the original bishop scoring system 1964 (Bishop EH, 1964) as seen in table 1.

Table 1: The Bishop score (Bishop EH, 1964):

0 points : for no dilation, effacement 0-30%, station -3, firm consistency \& posterior position of cervix

1. point : for dilation 1-2 cm, effacement 40-50%, station -2, medium consistency \& mid position of cervix.
2. points: for dilation 3-4 cm, effacement 60-70%, station -1, soft consistency \& Anterior position of cervix.
3. points: for dilation 5-6 cm, effacement 80%, station +1 or +2.

Sum of the points in each criteria assessed will be the bishop score.

Trans-vaginal ultrasound assessment of cervical length was performed using the same machine each time Sonoace x4 (samsung Medison Co., Ltd. Seoul, South Korea) following a standardized technique in which the bladder was emptied \& the vaginal probe 6.5MHz was introduced into the vagina and manipulated so that the main anatomical landmarks (bladder, fetal presentation, cervical canal, internal and external cervical os) were identified. The hyper echoic line extending from the internal os to external os, was identified by fine manipulations of the probe. The cervical canal length was measured as the distance between the internal and external os, while presence of funneling was recorded. Funneling was defined as a (V)or (U) shaped indentation of the internal os. In the presence of funneling, the length of an associated funnel was not included as part of the cervical length, and the measurement was taken from the apex of the funnel to the external os.

A modified bishop score was devised for the purpose of this study, which aimed to incorporate cervical length into the bishop scoring system. This score was calculated by addition or subtraction of the figure obtained respectively for cervical length in table 2 from the original bishop score.

Table 2: Scoring System for respective cervical length

Score: -2 for Cervical length > 2.5cm by trans-vaginal ultrasound. Score: -1 for Cervical length 2 - 2.5 cm by trans-vaginal ultrasound.

Score: 0 for Cervical length 1.6 - 1.9 cm by trans-vaginal ultrasound.

Score: +1 for Cervical length 1 - 1.5 cm by trans-vaginal ultrasound.

Score: +2 for Cervical length < 1 cm by trans-vaginal ultrasound.

We think an unfavorable score should decrease the value of the bishop score, and not just fail to increase it (in comparison to the original score) \& hence our negative value for unfavorable cervical length. The values used to set the figures for the max and min score for cervical length in table 2 were based on our observation of how several studies displayed the range of their results for cervical length and how we think that it should impact the bishop score. There is no exact pre-set cut off value for what a favorable cervical length should be.

Labour induction and Monitoring:

Induction of labor was carried out as per our hospital's standard protocol, in which patients with unfavorable cervical examination i.e. bishop score of 4 or less were given dinoprostone 3mg (Dinoglandin E2 ® Egypharma Nasr City Cairo Egypt) vaginal tablet, with re-dosing intervals every six hours if no significant cervical changes were noted.

In cases where the initial bishop score was 5 or more, or improvement was seen after dinoprostone, Oxytocin was initiated for induction. In cases already having one or more dinoprostone vaginal tablets, oxytocin was started four hours after the final dinoprostone dose, using the low-dose protocol beginning with 2 mU/min (and increase by 2 mU/min) at incremental time intervals (15 - 30 minutes). The goal was to reach satisfactory contractions (3-5 per ten minutes with each contraction lasting 45 seconds), \& to avoid uterine hyperstimulation.

All through induction \& labor fetal heart rate was measured every 30 minutes in first stage of labor and every 10 minutes in second stage of labor. Progress of labor was observed \& recorded, the total amount of oxytocin used, fetal weight and Apgar score for each baby were recorded. The total time taken till reaching active phase of labor, total time taken till delivery \& mode of delivery were recorded. Any decision to proceed to caesarean was reviewed by a senior consultant and the indication was noted. Any case undergoing caesarean for any indication other than failure of progress will be omitted from the results.