Cervical Length MeasurementObstetric Labor, PrematureCervix UteriFibronectinsUterine Cervical IncompetenceCervical RipeningTocolytic AgentsPregnancyLabor Stage, FirstCerclage, CervicalVaginaUltrasonography, PrenatalGestational AgePregnancy Trimester, SecondPregnancy, ProlongedPremature BirthExtraembryonic MembranesTwinsLabor, InducedPregnancy, TripletLabor OnsetReceptors, FibronectinGravidityPregnancy, High-RiskPregnancy Trimester, ThirdPregnancy OutcomePredictive Value of TestsSensitivity and SpecificityTocolysisAbortion, ThreatenedCesarean SectionUterine HemorrhagePregnancy, MultipleParityDelivery, ObstetricFetal Membranes, Premature RuptureHysteroscopyFetusPregnancy Trimester, FirstHydroxyprogesteronesROC CurveProspective StudiesUterine DiseasesUltrasonographyUltrasonography, Doppler, ColorPalpationTripletsPolyhydramniosOvarian CystsPessariesUterine ContractionBiological MarkersPlacenta PreviaAdministration, IntravaginalGlycoproteinsAmniocentesisOvarian DiseasesInfant, Newborn