AnencephalySpina Bifida OccultaSpinal DysraphismRecurrenceNeural Tube DefectsNeoplasm Recurrence, LocalEncephalocelePregnancyCongenital AbnormalitiesPregnancy, TwinRetrospective StudiesFollow-Up StudiesTreatment OutcomeFetal DeathFolic AcidDiseases in TwinsAmniotic Band SyndromeInfant, NewbornSurgical MeshFetal DiseasesPrognosisAmniotic FluidRisk FactorsPrenatal CarePrenatal DiagnosisPreconception CareFood, FortifiedHernia, InguinalCurettageNeoplasm Staging