PregnancyTwinsGestational AgePregnancy, MultiplePregnancy OutcomeInfant, NewbornUltrasonography, PrenatalBirth WeightTripletsPremature BirthMaternal AgePregnancy Trimester, FirstPregnancy Trimester, SecondPregnancy, TwinReproductive Techniques, AssistedInfant, Low Birth WeightPregnancy ComplicationsObstetric Labor, PrematureInfant, Small for Gestational AgeParityCesarean SectionCongenital AbnormalitiesMultiple Birth OffspringFertilization in VitroFetal Growth RetardationDelivery, ObstetricInfant MortalityPregnancy Trimester, ThirdDiseases in TwinsFetal WeightCrown-Rump LengthExpressed Sequence TagsObstetric Labor ComplicationsEmbryo TransferSperm Injections, IntracytoplasmicFetal DeathInfant, PrematureChorionic Gonadotropin, beta Subunit, HumanStillbirthLabor, InducedPregnancy, High-RiskFetal DevelopmentPre-EclampsiaBreech PresentationCohort StudiesUterine Cervical IncompetenceTwins, MonozygoticAbruptio PlacentaeTwins, DizygoticNuchal Translucency MeasurementRisk FactorsPregnancy-Associated Plasma Protein-AAbortion, SpontaneousDown SyndromeLabor PresentationFetusFetal Membranes, Premature RuptureUmbilical ArteriesPrenatal DiagnosisQuadrupletsProspective StudiesApgar ScoreHypertension, Pregnancy-InducedFetal HeartBirth CertificatesPlacentaDenmarkFetal MacrosomiaCardiotocographyRetrospective StudiesAbortion, ThreatenedFetal MonitoringBirth RateTerm BirthSingle Embryo TransferInfertilityHeart Rate, FetalInfant, Newborn, DiseasesHeadLabor Stage, SecondContig MappingCervical Length MeasurementPolyhydramniosParturitionPerinatal MortalityPregnancy Reduction, MultifetalChorioamnionitisCervix UteriLabor, ObstetricTrial of LaborFetal DistressEmbryonic and Fetal DevelopmentPrenatal CareReproductive TechniquesUltrasonography, DopplerFetal DiseasesGene LibraryPregnancy, ProlongedCryopreservationDiabetes, Gestational