TwinsDiseases in TwinsPregnancyTwins, MonozygoticTwins, ConjoinedTwins, DizygoticPregnancy OutcomePregnancy ComplicationsBirth WeightPregnancy, AnimalPregnancy, TwinPregnancy, EctopicPregnancy, MultiplePremature BirthTwin Studies as TopicPregnancy Trimester, FirstInfant, NewbornPregnancy Trimester, ThirdPregnancy RateInfant, Low Birth WeightGestational AgePregnancy Complications, CardiovascularPregnancy TrimestersBirth RatePregnancy TestsPregnancy Trimester, SecondPregnancy in DiabeticsPregnancy, TubalPregnancy in AdolescencePregnancy Complications, NeoplasticPregnancy Complications, InfectiousAbortion, SpontaneousFetal DeathPregnancy, High-RiskBirth OrderPregnancy, UnplannedPregnancy ProteinsBirth CertificatesPregnancy, UnwantedMaternal AgeUltrasonography, PrenatalPlacentaParityCongenital AbnormalitiesPregnancy Complications, HematologicPre-EclampsiaPrenatal CareEmbryo TransferPregnancy, ProlongedFertilization in VitroDelivery, ObstetricPregnancy Reduction, MultifetalCesarean SectionPrenatal Exposure Delayed EffectsAbortion, InducedTripletsObstetric Labor, PrematureRisk FactorsUterusPregnancy Complications, ParasiticMaternal-Fetal ExchangeCohort StudiesFetal DevelopmentBirth IntervalsPregnancy, AbdominalEmbryo ImplantationFetofetal TransfusionMaternal ExposurePregnancy MaintenanceInfant MortalityFetusLabor, ObstetricInfant, Small for Gestational AgeProspective StudiesReproductive Techniques, AssistedFetal Growth RetardationStillbirthMultiple Birth OffspringPrenatal DiagnosisAbnormalities, Drug-InducedHypertension, Pregnancy-InducedInfertility, FemaleLactationFetal DiseasesMothersRetrospective StudiesProgesteroneFertilitySperm Injections, IntracytoplasmicBirth InjuriesAbortion, TherapeuticDiabetes, GestationalGravidityPlacenta DiseasesChorionTime FactorsInfertilityObstetric Labor ComplicationsDeciduaInsemination, Artificial