Bed RestMultiple Birth OffspringPremature BirthPregnancy, MultipleInfant, NewbornPregnancyBirth WeightInfant, PrematureInfant, Low Birth WeightTripletsBirth RatePregnancy OutcomeGestational AgeObstetric Labor, PrematureCongenital AbnormalitiesHead-Down TiltQuadrupletsInfant MortalityFetal DeathWeightlessness SimulationMaternal AgeReproductive Techniques, AssistedPregnancy ComplicationsInfant, Premature, DiseasesTwinsWeightlessness CountermeasuresRestBirth OrderAbortion, VeterinaryAbortion, SpontaneousCardiovascular DeconditioningBronchopulmonary DysplasiaBirth CertificatesRisk FactorsInfant, Small for Gestational AgeSpace FlightBedsEmbryo TransferFertilization in VitroPregnancy Complications, InfectiousRespiratory Distress Syndrome, NewbornAnimals, NewbornWeightlessnessPerinatal CareDelivery, ObstetricRetrospective StudiesInfertilityPregnancy Reduction, MultifetalOrthostatic IntoleranceLive BirthVital StatisticsIntensive Care Units, NeonatalCesarean SectionFertility Agents, FemalePrenatal CareUnited StatesLower Body Negative PressureParityIntensive Care, NeonatalSingle Embryo TransferSperm Injections, IntracytoplasmicBirth IntervalsOvulation InductionLogistic ModelsCohort StudiesRegistriesBirth InjuriesEnglandCryopreservationCerebral PalsyInfant, Very Low Birth WeightIncidenceOdds RatioAge FactorsBed OccupancyTime FactorsWalesPopulation SurveillanceSupine PositionPregnancy RateMuscle, SkeletalMuscular AtrophyExercisePlasma VolumeEarly AmbulationPrevalenceHypotension, OrthostaticCase-Control StudiesVaginal Birth after CesareanNigeriaRepublic of KoreaHypovolemiaRiskAmino Acids, EssentialVascular CapacitanceImmobilizationGreat BritainHome Childbirth