Sonographic Cervical Assessment To Predict The Success of Labor Induction

Abstract

Inductionoflaboristheartificialinitiationof uterinecontraction prior totheirspontaneous onsetleading toprogressive dilatationandeffacementofthe cervixand delivery ofthebaby.Theterm usuallyrestrictedto pregnanciesatgestationsgreaterthanthelegaldefinition of the fetalviability. Therate ofinductionvarieswidely indifferent countriesand unitsandbetweenindividual obstetricians withinthesameunit.Suchvariation may bedueto differencesintheindicationsforinduction,definitions (e.g.postmaturityorhypertension),availabilityof resourcesaswellasunexplaineddifferencesinopinion andpractice.Post-term pregnancy isthemostcommon indicationforinduction. Potentialrisksof inductionincludeincreasedrateof operativevaginaldelivery,caesareanbirth,excessive uterineactivity, abnormalfetalheartrate patterns, uterine rupture,maternalwaterintoxication,delivery ofpreterm infantdue toincorrectestimationof dates,and possibly cordprolapse withartificialruptureofmembranes.Allof thatmandatethefindingofanappropriateandaccurate wayforpredictionofthe successrate of this processand justificationofitsresults. TheBishop score hasapoorpredictive valuefor the induction of labor.Itwasfoundthatamong theBishop Scorecomponentsonly dilatationandlength(effacement) haveshownasignificantcorrelationwithsuccessful vaginaldelivery. Bishop score has severallimitations in itsclinical application.First, very fewpatientshavehighscores. Second,many patientswithlower scoreshave successful inductions.Nevertheless,lowBishopScoreshave been associatedwithhighercesareansectionratesand prolongedlabor.Inaddition,there arestillsome degreesof subjectivityinthe scoringof effacement. Theoretically,transvaginalultrasonographic measurementscouldrepresenta more accurateassessment of the cervixthan the digitalexamination becausethe supravaginalportionofthecervixusuallycomprisesabout50% ofcervicallength, butthisishighly variableamong individuals. Thisportionisdifficulttoassessdigitally.In addition,effacementissubjectiveandcanvary considerably amongexaminers.Moreover,effacementis difficulttodetermineintheclosedcervix.Incontrast transvaginalultrasonographiccervicalmeasurementisa goodquantitative method. Somestudiessupposedthattransvaginal ultrasonographic measurement ofcervical length doesnot addany additionalbenefittothepredictionofcervical inducibilityobtainedbythe Bishopscore. Also, otherstudiesrecommendedthatBishopScore wasasuperiormethodforpredictionof successfullabor inductionthantotheuseofultrasonographicaly measured cervicallength. ThisstudywasconductedattheAin-shams UniversityMaternityhospitalouraim from thestudyisto determinetherole ofrole of sonographiccervical length andModifiedBishopScoreinpreinductioncervical assessmentwhere 182women 37-43weeks pregnancy undergoinginductionoflabourusing3mgPGE2 vaginally.Thedosesweregivenat6 hours intervalfor maximum of4doses.Beforeinductiontheattending obstetricianperformedadigitalexamination ofthecervix and noted the ModifiedBishop score.Cervical lengthwas thenmeasuredby atransvaginalultrasoundscanner.And whenuterinecontractionsstartexternalCardiotocoGraphy wasregularlyperformedtomonitortheconditionofthe fetus. Induction oflabor for variousindicationswere recruitedin the currentstudy.Theindicationfor induction oflaborwaspostdate pregnancy (69.2%)followedby pregnancy-induced hypertension(19.8%).Transvaginal ultrasonography wasperformedforallpatientsinvolvedin thestudy.Patientsrecruitedhadameanageof23+3.7 (17-35)yearsandamediangestationof40.3+4(37-43)weeks. Vaginaldeliverywasachievedin143(78.5%)women.39(21.5%)deliverieswerebycaesareansection,5(12.8%) ofwhichwereforfailure to progressingroupA and5(12.8%) for groupB,13(33.3%)for failedinduction ingroupAand9(23.1%)forgroupB,and2(5.1%)for fetaldistressingroupAand5(12.78%) forgroupB. Statistical analysis revealed that cervical length was the mostsensitive(87.6%),Modified Bishop(61.25%)and specificpredictorofsuccessfullaborinduction(91.2%) thenModified theBishopscore(74.5%)for the prediction of successfullaborinduction.