TwinsDiseases in TwinsTwins, MonozygoticTwins, ConjoinedTwins, DizygoticBirth WeightTwin Studies as TopicPregnancy, TwinPremature BirthBirth RateInfant, Low Birth WeightPregnancyInfant, NewbornBirth OrderPregnancy, MultipleBirth CertificatesGestational AgePregnancy OutcomeBirth IntervalsFetofetal TransfusionTripletsMaternal AgeMultiple Birth OffspringCongenital AbnormalitiesFetal DeathInfant MortalityBirth InjuriesDelivery, ObstetricCohort StudiesPregnancy ComplicationsRisk FactorsParityInfant, Small for Gestational AgeEnvironmentCesarean SectionUltrasonography, PrenatalObstetric Labor, PrematureRegistriesPregnancy Reduction, MultifetalVaginal Birth after CesareanAnimals, NewbornFetal DevelopmentPrenatal CareMothersReproductive Techniques, AssistedDenmarkPrenatal Exposure Delayed EffectsChorionHome ChildbirthMaternal ExposureChild DevelopmentApgar ScoreSwedenPerinatal CareStillbirthGene-Environment InteractionGenetics, BehavioralFertilization in VitroLongitudinal StudiesEmbryo TransferAge FactorsMidwiferyInfant, Premature, DiseasesProspective StudiesBody HeightTwinning, MonozygoticRetrospective StudiesObstetric Labor ComplicationsSocial EnvironmentPaternal AgeFetusPregnancy Trimester, SecondPhenotypeSex RatioQuadrupletsFetoscopyPerinatal MortalitySex FactorsFinlandBody WeightLabor, ObstetricRegression AnalysisOdds RatioSocioeconomic FactorsLogistic ModelsPrevalenceUnited StatesPolyhydramniosBreast FeedingPlacentaAbortion, SpontaneousGenetic Predisposition to DiseaseIntensive Care Units, NeonatalPregnancy in AdolescencePregnancy Trimester, ThirdEducational StatusSiblingsPrenatal DiagnosisWeight GainDystocia