TwinsDiseases in TwinsPregnancyTwins, MonozygoticFetusTwins, ConjoinedTwins, DizygoticPregnancy OutcomePregnancy ComplicationsPregnancy, AnimalPregnancy, TwinPregnancy, EctopicPregnancy, MultipleTwin Studies as TopicPregnancy Trimester, FirstPregnancy Trimester, ThirdGestational AgePregnancy Trimester, SecondPregnancy RatePregnancy Complications, CardiovascularUltrasonography, PrenatalPregnancy TrimestersPregnancy TestsPregnancy in DiabeticsCampylobacter fetusPregnancy, TubalFetal DiseasesPregnancy Complications, NeoplasticFetal DeathInfant, NewbornPlacentaTritrichomonas foetusPregnancy in AdolescenceAbortion, SpontaneousPregnancy Complications, InfectiousPregnancy, High-RiskMaternal-Fetal ExchangePregnancy ProteinsFetal Growth RetardationPregnancy, UnplannedPregnancy, UnwantedPrenatal DiagnosisPregnancy Complications, HematologicFetal DevelopmentPre-EclampsiaPregnancy Reduction, MultifetalUterusPregnancy, ProlongedAbortion, InducedEmbryo TransferFertilization in VitroPregnancy, AbdominalBirth WeightFetal HeartFetofetal TransfusionTripletsMaternal AgeAmniotic FluidPregnancy Complications, ParasiticPrenatal Exposure Delayed EffectsEmbryo ImplantationPrenatal CarePregnancy MaintenanceCesarean SectionCongenital AbnormalitiesParitySheepAbnormalities, Drug-InducedFetal WeightEmbryonic and Fetal DevelopmentPremature BirthUmbilical ArteriesObstetric Labor, PrematureAbortion, TherapeuticDelivery, ObstetricAbortion, VeterinaryHeart Rate, FetalLabor, ObstetricAmniocentesisProspective StudiesProgesteroneHypertension, Pregnancy-InducedCrown-Rump LengthRisk FactorsMaternal ExposureChorionFetal BloodInfertility, FemaleLactationPlacenta DiseasesFetal MonitoringTrophoblastsDeciduaRetrospective StudiesReproductive Techniques, AssistedCohort StudiesSperm Injections, IntracytoplasmicDiabetes, GestationalHydrops FetalisDown Syndrome