Umbilical vascular coiling and nuchal entanglement.

We have frequently observed that fetuses born with nuchal cords have umbilical cords that contain less vascular coiling. To study the association between umbilical vascular coiling and nuchal entanglement, the density of umbilical coiling was objectively assessed in relationship to nuchal entanglement of the umbilical cord using the "umbilical coiling index" in 200 consecutive liveborn neonates. The umbilical coiling index of each cord was determined by dividing the number of complete vascular coils by the total length of the cord in centimeters. The mean umbilical coiling index among those with nuchal cords (0.18 +/- 0.09 coils/cm) was significantly less than that among the group without nuchal entanglement (0.21 +/- 0.07 coils/cm), P = 0.01. Among those with umbilical coiling indices < or = 0.10 coils/cm, 42% had nuchal cords, while only 4.8% of cords with indices > or = 0.30 coil/cm had nuchal cords (P = 0.007). It is concluded that a relationship exists between the density of umbilical vascular coiling and nuchal entanglement of the cord.