Transvaginal Sonographic Measurement of Cervical Length as a Predictor of the Success of Induction of Labor

Abstract

Between 1990 and 2012, the overall frequency of labor induction more than doubled, rising from 9.5 to 23.3 percent and early term (in the 37th and 38th week of gestation) inductions quadrupled, rising from 2 to 8 percent over a similar period of time. The Bishop score, since its description in 1964, remains the gold standard for assessing favorability for induction of labor. However, the preinduction ‘favorability’ of the cervix as assessed by the Bishop score is very subjective and several studies have demonstrated a poor predictive value for the outcome of induction especially in women with a low Bishop score. Thus the aim of the present study was to assess the accuracy of transvaginal measurement of cervical length prior to induction of labor in prediction of successful induction. The currentstudy was conducted prospectively in Ain Shams University Maternity Hospital.100 women with singleton term pregnancies cephalic presentation scheduled to undergo labor induction at ≥37 gestation were recruited to this study. Transabdominal ultrasonographic examination was performed .Then the length of the cervix was measured from the outer to the inner cervical os as a straight line by a transvaginal ultrasound and posterior cervical angle with fetal head was calculated by the same gynecologist. Following this a digital vaginal examination was performed to evaluate the status of the uterine cervix and determine the Bishop score,Induction of labor was performed byinserting Dinoprostone 3 mgin the posterior vaginal fornix, repeated if needed every 6 h for up to two doses.Number of doses of prostaglandins range from 0-2 tablets, the meannumber of doses of prostaglandins (± standard deviation [SD]) was 1.65 (±0.59), when the cervix became favorable and no regular contractions were observed, amniotomy and oxytocin augmentation, starting at1 mIU/min and increasing 1 mIU every 30 min as necessary, oxytocin used range from 5-15 IU the mean IU of oxytocin were 8.74(± 3.75). Inthecurrentstudy,(76%)ofour100participantsweredeliveredvaginallyand(24%)womenweredeliveredby CS.Themeanageofourparticipantswas24.16(±3.59)years,themeanBMI(kg/m2)was25(±3.00)andthemeangestationalagewas39.75(±1.29)weeks. Themeanageofpatientsdeliveredvaginallywas24.04(±3.65),themeanageofpatientsdeliveredby CS.was24.54(±3.65),themeanBMIofpatientsdeliveredvaginallywas24.10(±2.77),themeanBMIofpatientsdeliveredby CS.was25.73(±3.06).themeangestationalageofpatientsdeliveredvaginallywas39.76(±1.29)andthemeangestationalageofpatientsdeliveredby CS.was39.71(±1.30). Therewasnostatisticallysignificantcorrelationbetweenage,gestationalageandthesuccessof labor induction(VD),howevertherewasastatisticallysignificantpositivecorrelationbetweenincreasedBMIandfailureof labor induction(CS). Inthecurrentstudy,bothnulliparousandmultiparouswomenwererecruited36womenwerePrimigravidaand64womenweremultipara.72.2%ofprimigravidasdeliveredvaginallyand27.8%ofthemdeliveredby CS,76%ofmultiparadeliveredvaginallyand24%ofthemdeliveredby CS,Therewasnostatisticallysignificantcorrelationbetweenparityandthesuccessof labor induction(pvalue0.507). Inthecurrentstudy,inductionwasindicatedformedicalandobstetricreasons.ThemostcommoncauseofinductionwasROM(46females)37ofthemhavedeliveredvaginallyfollowedby postdate (37females)27ofthemhavedeliveredvaginally,PIH(females)12ofthemhavedeliveredvaginally,therewasnostatisticallysignificantcorrelationbetweenindicationsofinductionandsuccessofinductionof labor (pvalue0.620).