- Placental sonografic findings : placental degeneration , increased thickness , cystic images and the tendency toward increased volume and echogenicity as pregnancy progresses.
- Single umbilical artery is a sonographic sign associated with a wide range of syndromes , perinatal complications , intrauterine growth restriction and fetal malformations , chromosomal defects (especially trisomy 18).
- Umbilical cord pseudocyst has been associated with fetal chromosome abnormalities , in particular trisomia 13 and 18 .
- Yolk sac : its size can be considered as a predicitive factor of wellbeing in pregnancy ; a decrease in yolk sac diameter has been suggested to be a marker of aneuploidy when accompanied by the decreased levels of maternal serum alphafetopritein seen in trisomic fetuses .
- Ventricular echogenic focus : it has been associated with cardiac tumors and chromosomal defects .
- Bilateral pyelectasia is an additional sign in the ultrasound screening of trisomy 21 .