Cervical Length MeasurementCervix UteriObstetric Labor, PrematureUterine Cervical IncompetenceCervical RipeningCerclage, CervicalPregnancy, ProlongedPregnancy Trimester, SecondUltrasonography, PrenatalPremature BirthLabor, InducedLabor OnsetPregnancyGestational AgeGravidityPregnancy Trimester, ThirdPregnancy, High-RiskTocolysisAbortion, ThreatenedParityPregnancy, MultipleCesarean SectionDelivery, ObstetricFetal Membranes, Premature RuptureHydroxyprogesteronesPregnancy OutcomeTwinsTripletsPolyhydramniosROC CurveLabor Stage, FirstUterine ContractionPessariesVaginaAdministration, IntravaginalAmniocentesisProspective StudiesPredictive Value of TestsPalpationTerm BirthPregnancy, TwinExtraembryonic MembranesProgestinsSensitivity and SpecificityCervix MucusMaternal AgeTocolytic AgentsUterine Cervical DiseasesPregnancy Trimester, FirstPerineumLength of StayUterine HemorrhageAbortion, InducedChorioamnionitisRegression AnalysisFetoscopyLogistic ModelsPlacenta PreviaRisk FactorsBed RestAmniotic FluidRisk AssessmentLabor, ObstetricUterine CervicitisSuture TechniquesAmnionObserver VariationReference ValuesInfant, NewbornPolymorphism, Restriction Fragment LengthAbdomenFeasibility StudiesProbabilityInsulin-Like Growth Factor Binding Protein 1Reproducibility of ResultsUltrasonographyTime FactorsUrinationInfant, PrematureEpidemiologic MethodsLinear ModelsStatistics, NonparametricFibronectinsPregnancy Complications, InfectiousRetrospective StudiesCohort StudiesPregnancy ComplicationsPlacebosProgesteroneUrinary Bladder