Biochemical differences related to birth order in triplets.

This is the first report to date on biochemical parameters in triplets. Umbilical artery and venous pH, PO2, PCO2, lactate and base deficit were measured in seven sets of triplets. Other parameters compared were route of delivery, one- and five-minute Apgar score, birth weight, relative birth order and sex. Twenty-one viable infants were born from three induced and four spontaneous pregnancies. Female: male sex ratio was 1.6:1.0. All triplets within a set were delivered by the same route--six sets by cesarean section and one set vaginally. There were no significant differences, according to Student's t-test, in birth weight, Apgar scores and biochemical parameters related to birth order. Comparison of umbilical artery and umbilical venous pH, PO2, PCO2, lactate and base deficit differences did not demonstrate evidence of acidosis or significant base deficit in the third triplet when compared with the first two, suggesting that the duration in utero after deliver of the firstborn is not associated with metabolic acidosis or hypoxia in the absence of any obstetric complication or anesthetic problem.