IliumNasal BoneBone and BonesDown SyndromeSacrumNasal MucosaCrown-Rump LengthPelvic BonesUltrasonography, PrenatalBone NeoplasmsNuchal Translucency MeasurementPregnancy Trimester, FirstBone RemodelingAcetabulumPregnancy Trimester, SecondSternumBone DensitySkull FracturesNasal PolypsNasal SeptumGestational AgePregnancyBone ResorptionMaternal AgeBone MarrowChorionic Villi SamplingNasal Lavage FluidChromosomes, Human, 16-18Chorionic Gonadotropin, beta Subunit, HumanPregnancy-Associated Plasma Protein-A