MortalityHospital MortalityInfant MortalityCause of DeathChild MortalityMaternal MortalityCohort StudiesRetrospective StudiesFollow-Up StudiesProportional Hazards ModelsTime FactorsTreatment OutcomeProspective StudiesSurvival AnalysisSurvival RateUnited StatesCardiovascular DiseasesRisk AssessmentInfant, NewbornMortality, PrematureAge FactorsPerinatal MortalityIncidencePrognosis