Fetal HeartHeart Rate, FetalHeartHeart RateFetal MonitoringArrhythmia, SinusCardiotocographySympathetic Fibers, PostganglionicPregnancyUltrasonography, PrenatalHeart Defects, CongenitalEchocardiography, Four-DimensionalSympathetic Nervous SystemFetal MovementPeroneal NerveElectrocardiographyFetal DiseasesGestational AgeFetal DistressFetal HypoxiaRespirationInhalationSinoatrial NodeMyocardial ContractionModels, CardiovascularUmbilical ArteriesMyocardiumHeart FailureSignal Processing, Computer-AssistedFetusBlood PressurePressoreceptorsHeart BlockCanrenoic AcidRestPregnancy Trimester, SecondHeart DiseasesEchocardiography, Three-DimensionalHeart VentriclesMagnetocardiographyTime FactorsHeart TransplantationUltrasonography, DopplerHeart ValvesPregnancy Trimester, ThirdBradycardiaPregnancy Trimester, FirstLabor, ObstetricCardiac VolumeOxygen ConsumptionAlgorithmsEchocardiographyAction PotentialsHemodynamicsPregnancy OutcomeHeart AtriaFetal DevelopmentAbortion, ThreatenedBlood Flow VelocityPrenatal DiagnosisSheepMaternal-Fetal ExchangeMyocytes, CardiacEchocardiography, Doppler, ColorProspective StudiesApgar ScoreTachycardiaFetal Growth RetardationInfant, NewbornPerinatologyCrown-Rump LengthHeart SeptumElectronics, MedicalPregnancy ComplicationsAnalgesia, ObstetricalPregnancy, High-RiskPlacental CirculationCardiomegalyHeart Function TestsHeart AuscultationAnesthesia, ObstetricalHeart Arrest, InducedSensitivity and SpecificityTocolytic AgentsMyocardial IschemiaDogsFeasibility StudiesUmbilical CordCardiac Pacing, ArtificialSheep, DomesticCesarean SectionDown SyndromeSufentanilReproducibility of ResultsVentricular Function, LeftUltrasonography, Doppler, ColorReference ValuesEchocardiography, DopplerCoronary DiseaseUltrasonography