Bed RestPregnancy, MultiplePregnancyPregnancy OutcomePregnancy Reduction, MultifetalTripletsPregnancy RatePregnancy ComplicationsHead-Down TiltEmbryo TransferWeightlessness SimulationTwinsWeightlessness CountermeasuresFertilization in VitroPregnancy, TwinRestReproductive Techniques, AssistedSingle Embryo TransferReproductive TechniquesInsemination, ArtificialPregnancy, AnimalOvulation InductionPregnancy, EctopicMultiple Birth OffspringCardiovascular DeconditioningPregnancy Trimester, FirstPregnancy, High-RiskEmbryo ImplantationMaternal AgeSpace FlightAbortion, SpontaneousGestational AgeInfertilityInfertility, FemaleFetal DeathBedsCongenital AbnormalitiesLive BirthSperm Injections, IntracytoplasmicInfant, NewbornMenotropinsInsemination, Artificial, HomologousPregnancy Trimester, SecondParityWeightlessnessPregnancy Trimester, ThirdPremature BirthClomipheneCryopreservationUltrasonography, PrenatalOocyte DonationPregnancy Complications, CardiovascularPregnancy TrimestersPregnancy TestsFertility Agents, FemaleChorionTwins, MonozygoticOrthostatic IntoleranceDelivery, ObstetricPregnancy in DiabeticsPre-EclampsiaHypertension, Pregnancy-InducedObstetric Labor, PrematureBirth WeightPregnancy, TubalGonadotropinsFertility AgentsPregnancy Complications, NeoplasticPregnancy in AdolescenceCervical Length MeasurementLower Body Negative PressureInfant MortalityPregnancy Complications, InfectiousPrenatal CareCesarean SectionRetrospective StudiesOvarian Hyperstimulation SyndromeTime FactorsGamete Intrafallopian TransferRisk FactorsPerinatal MortalityPregnancy ProteinsPregnancy, UnplannedChorionic GonadotropinBirth RatePregnancy, UnwantedAnovulationPolycystic Ovary SyndromeFetofetal TransfusionHydroxyprogesteronesFollicle Stimulating HormoneFertilizationPregnancy Complications, HematologicProspective StudiesDiseases in TwinsTreatment OutcomeOvarian FollicleBed OccupancyUmbilical CordPlacenta