Umbilical cord length and acid-base balance at delivery.

An abnormally short or long umbilical cord is associated with a greater risk of cord compression, variable fetal heart rate decelerations and fetal demise. The purpose of the present investigation was to determine whether any relation exists between an abnormal length of the umbilical cord and acid-base imbalance at delivery. Cord lengths were measured routinely in 3,019 consecutive pregnancies undergoing labor beyond 34 weeks. Short cords (13-35 cm) were found in 61 (2.0%) cases and long cords (80-121 cm) in 112 (3.7%) cases. Umbilical blood pH and base deficit values averaged the same for those pregnancies with short (7.35 +/- 0.09 and 3.1 +/- 2.7 mEq/L, mean +/- SD), normal length (7.36 +/- 0.03 and 3.8 +/- 1.7, mEq/L) and long (7.34 +/- 0.06 and 3.7 +/- 3.1 mEq/L) cords. A blood pH < 7.20 was very uncommon in the presence of a short (two cases, 3.3%) or long (five cases, 4.5%) cord and was accompanied by an abnormal fetal heart rate pattern, such as severe variable decelerations or bradycardia. Finding an abnormally short or long umbilical cord at birth is not by itself associated with an increased risk of acid-base imbalance at delivery and does not require routine cord blood gas determination.