Nuchal CordPlacentaUmbilical CordNeckSpinal CordPregnancyUltrasonography, PrenatalUltrasonography, Doppler, ColorPregnancy Trimester, ThirdObstetric Labor ComplicationsSpinal Cord InjuriesPlacenta DiseasesPregnancy Trimester, FirstPlacenta PreviaPlacenta AccretaPlacenta, RetainedGestational AgePregnancy OutcomeTrophoblastsPredictive Value of TestsMaternal-Fetal ExchangeSensitivity and SpecificityChorionic Villi