Placenta - Cord
Cord Vessel Number
There are few abnormalities associated with umbilical cord development, other that abnormally short or long cords, which in most cases do not cause difficulties.
In some cases though, long cords can wrap around limbs or the fetus neck, which can then restrict blood flow or lead to tissue or nerve damage, and therefore effect develoment.
Cord knotting can also occur (1%) in most cases these knots have no effect, in some cases of severe knotting this can prevents the passage of placental blood.
See WebPath images: umbilical cord knot 1 | umbilical cord knot 2 | Pseudoknot of umbilical cord, gross
Umbilical cord torsion
Rare umbilical cord torsion, even without knot formation can also affect placental blood flow, even leading to fetal demise.
Hallak M, Pryde PG, Qureshi F, Johnson MP, Jacques SM, Evans MI. Constriction of the umbilical cord leading to fetal death. A report of three cases. J Reprod Med. 1994 Jul;39(7):561-5. Review.
See WebPath images: Torsion of umbilical cord, gross | Torsion of umbilical cord, with fetal demise, gross