Apr 1, 1985

Differences in twins: the importance of birth order

American Journal of Obstetrics and Gynecology
B K YoungJ Wasserman


Despite the clinical impression that firstborn twins do better than second-born twins, recent reports have shown no difference in perinatal mortality between them. In order to evaluate differences in twins, more sensitive means than perinatal deaths are necessary. This study examines differences between 80 firstborn and second-born twin pairs with respect to Apgar score, umbilical venous and arterial blood gas, and acid-base data. The umbilical venous and arterial blood PO2, PCO2, base deficit, pH, and lactic acid concentration were measured in paired samples and compared with the paired t test and chi 2 when applicable. Statistically significant differences favoring twin A, the firstborn, were found in 1-minute Apgar score, umbilical venous pH, PO2, and PCO2, and umbilical arterial PO2. The other factors in umbilical venous and arterial blood did not show statistically significant differences. When these parameters were examined with respect to route of delivery, monochorionic and dichorionic twins, interval between twins, and vertex twins only, with the possible effects of malpresentation eliminated, the results persistently favored the firstborn twin. Thus it is unequivocally demonstrated that there are substantial differenc...Continue Reading

  • References2
  • Citations31


  • References2
  • Citations31


Mentioned in this Paper

Umbilicus (Anatomy)
Oxygen Measurement, Partial Pressure, Arterial
Ammonium lactate
Lactic Acid Measurement
Analysis of Arterial Blood Gases and pH

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