Umbilical cord arterial and venous blood gas values were compared in 63 twin pairs, of which 57 pairs had birth weights of 1500 g or more each. Small differences between the first and second twins existed for PO2, PCO2, and pH. However, bicarbonate values did not differ significantly. These cord gas differences represent minor respiratory aberrations, as reflected by a tendency toward carbon dioxide retention by the second twin. Route of delivery, time interval between deliveries, and nonvertex presentations were not associated with significant deviations from these observed acid-base patterns.
(C) 1990 The American College of Obstetricians and Gynecologists