Biphasic Postnatal Umbilical Cord Shortening

Introduction: Variations in postnatal length of refrigerated, unfixed umbilical cords were studied over time to elucidate natural changes and times of stability. Methods: Length was measured in 132 cords following severance, repeated at varying timed intervals and studied by analysis of variance and regression analysis. Results: Data show immediate rapid initial phase shortening (mean 4.2+/-3.9 cm SD); an interval of lengthening; stable length at hours 3-4 following severance, a slower second phase shortening (mean 1.5+/-0.7 cm SD) beginning at 5 hours and peaking at 12 hours; and gradual lengthening to stable length after 23 hours. Overall, there was a significant net mean decrease of 3.49+/-2.29 cm SD. Shortening was greatest for intact long cord segments (p=0.0001), as much as 11 cm. Two highly significant models for predicting umbilical cord length at delivery (OL) were determined using the post-delivery lengths (Length) measured at different times following delivery (Hours), as follows: At ≤ 3 hours following delivery: OL=1.02xLength cm+1.11xHours At >3 hours following delivery: OL=1.07xLength+0.44xHours-0.01x(Hours)2 Conclusion: Cord lengths stabilized between hours 3-4 and after 23 hours following severance. Phase one shortening resembles vasoconstriction; phase two resembles rigor mortis. The models allow prediction of the original umbilical cord length at delivery, regardless of the time of measurement.