Down SyndromeSyndromeChromosomes, Human, Pair 21Prenatal DiagnosisTrisomyMaternal AgeMetabolic Syndrome XEstriolPregnancy Trimester, SecondPregnancyAmniocentesisLeukemia, Megakaryoblastic, AcuteFetal DiseasesChromosomes, Human, 21-22 and YNephrotic SyndromeAbortion, EugenicSjogren's SyndromeIntellectual DisabilityInfant, NewbornTurner SyndromeKaryotypingAbnormalities, Multiplealpha-FetoproteinsNasal BoneNuchal Translucency MeasurementNondisjunction, GeneticUltrasonography, PrenatalPregnancy, High-RiskPregnancy Trimester, FirstWilliams SyndromeMyelodysplastic SyndromesPregnancy-Associated Plasma Protein-AChorionic Gonadotropin, beta Subunit, HumanCushing SyndromeFalse Positive ReactionsHeart Defects, CongenitalDisease Models, AnimalPhenotypePaternal AgeAcute Coronary SyndromePolycystic Ovary SyndromeChromosome DisordersCase-Control StudiesDiGeorge SyndromeHorner SyndromeCraniofacial AbnormalitiesPrader-Willi SyndromeLong QT SyndromeStanford-Binet TestHeart Septal DefectsRisk FactorsGuillain-Barre SyndromeHemolytic-Uremic SyndromeAlzheimer DiseaseDuodenal ObstructionMutationGenetic TestingCompartment SyndromesGATA1 Transcription FactorTourette SyndromeBiological MarkersChorionic GonadotropinRetrospective StudiesAntiphospholipid SyndromePedigreeMosaicismGestational AgeBrainPorcine Reproductive and Respiratory SyndromeKlinefelter SyndromePrevalenceNeck