Birth WeightPremature BirthPregnancyInfant, NewbornInfant, Low Birth WeightGestational AgePregnancy OutcomeMaternal AgeBirth CertificatesTwinsBirth RatePregnancy ComplicationsPregnancy, MultipleInfant MortalityTripletsCongenital AbnormalitiesReproductive Techniques, AssistedParityCesarean SectionInfant, Small for Gestational AgeDelivery, ObstetricStillbirthMaternal ExposureInfant, PrematureLive BirthCohort StudiesRisk FactorsFetal Growth RetardationFertilization in VitroPre-EclampsiaRegistriesOdds RatioBirth OrderUltrasonography, PrenatalRetrospective StudiesMultiple Birth OffspringLogistic ModelsSocial ClassObstetric Labor, PrematurePregnancy Trimester, SecondRegression AnalysisPregnancy Trimester, FirstSocioeconomic FactorsPregnancy, TwinBirth IntervalsUnited StatesFetal DeathPregnancy Trimester, ThirdObstetric Labor ComplicationsFetal DevelopmentBirth InjuriesDiseases in TwinsEmbryo TransferCrown-Rump LengthPregnancy, High-RiskLabor, InducedVaginal Birth after CesareanSperm Injections, IntracytoplasmicPrenatal CareFetal WeightExpressed Sequence TagsApgar ScoreProspective StudiesFetusMothersAbortion, SpontaneousPerinatal CareChild DevelopmentBreech PresentationChorionic Gonadotropin, beta Subunit, HumanPrenatal Exposure Delayed EffectsTwins, MonozygoticTwins, DizygoticLabor, ObstetricFetal MacrosomiaDenmarkPrenatal DiagnosisAbruptio PlacentaePerinatal MortalityFetal Membranes, Premature RupturePlacentaUterine Cervical IncompetenceBody HeightEmbryonic and Fetal DevelopmentHypertension, Pregnancy-InducedHome ChildbirthQuadrupletsLabor PresentationUmbilical ArteriesInfant WelfareInfant, Premature, DiseasesHeadNuchal Translucency MeasurementInfertilityFetal MonitoringPregnancy-Associated Plasma Protein-AFetal DiseasesGravidityFetal HeartIntensive Care, Neonatal