Down SyndromeSyndromeChromosomes, Human, Pair 21Prenatal DiagnosisTrisomyMaternal AgeMetabolic Syndrome XPregnancy Trimester, SecondEstriolPregnancyAmniocentesisLeukemia, Megakaryoblastic, AcuteFetal DiseasesChromosomes, Human, 21-22 and YNephrotic SyndromeAbortion, EugenicSjogren's SyndromeIntellectual DisabilityInfant, NewbornTurner SyndromeKaryotypingAbnormalities, Multiplealpha-FetoproteinsNasal BoneNuchal Translucency MeasurementUltrasonography, PrenatalNondisjunction, GeneticPregnancy, High-RiskPregnancy Trimester, FirstWilliams SyndromeMyelodysplastic SyndromesPregnancy-Associated Plasma Protein-AChorionic Gonadotropin, beta Subunit, HumanDisease Models, AnimalCushing SyndromePhenotypeFalse Positive ReactionsHeart Defects, CongenitalPaternal AgeAcute Coronary SyndromePolycystic Ovary SyndromeChromosome DisordersCase-Control StudiesDiGeorge SyndromeHorner SyndromeCraniofacial AbnormalitiesLong QT SyndromePrader-Willi SyndromeStanford-Binet TestHeart Septal DefectsMutationGuillain-Barre SyndromeRisk FactorsBrainAlzheimer DiseaseDuodenal ObstructionHemolytic-Uremic SyndromeBiological MarkersGenetic TestingCompartment SyndromesPedigreeGATA1 Transcription FactorTourette SyndromeChorionic GonadotropinGestational AgePrevalenceAntiphospholipid SyndromeRetrospective StudiesMosaicismPorcine Reproductive and Respiratory SyndromeNeckTime FactorsKlinefelter SyndromeProspective Studies