Chorionic VilliChorionic Villi SamplingPrenatal DiagnosisKaryotypingPregnancySpectral KaryotypingAmniocentesisPregnancy Trimester, FirstChromosome DisordersFetal DiseasesTrophoblastsPlacentaChromosome AberrationsTrisomyUltrasonography, PrenatalAneuploidyDown SyndromeGestational AgeFetomaternal TransfusionAbortion, SpontaneousNeckPregnancy, High-RiskPregnancy, TubalMaternal AgeAmniotic FluidIn Situ Hybridization, FluorescenceMosaicismMethemalbuminChorionCrown-Rump LengthPlacentationKaryotypePregnancy Trimester, SecondNuchal Translucency MeasurementCordocentesisChromosomes, Human, Pair 18