[Effects of delivery positions on the onset of first cry and umbilical blood gas parameters].

Physiological evaluation of sitting delivery position has not been well demonstrated. We measured the duration of 'the first cry occurrence time' both in supine (n = 54) and in sitting (n = 128) delivery positions. Umbilical blood gas analysis data were obtained from 130 pregnant women in sitting and 50 in supine delivery positions. To elucidate the mechanism of fetal blood gas differences due to posture, we also analyzed the maternal arterial blood gas during delivery (n = 145) and prior to labor (n = 100) in both positions. The first cry occurrence time was significantly shorter (p less than 0.01) in the sitting group. A weak negative correlation (r = -0.355, p less than 0.01) was found between the umbilical pH and the first cry occurrence time. Blood gas values for the umbilical vein and artery in the sitting group were significantly higher in pH, Po2, BE and Sao2, and lower in Pco2. Maternal blood gas values not only at delivery but also before labor did not elicit any significant differences between the two groups. It is suggested that the infants who have a high pH in their umbilical vessels cry sooner than those with a low pH. The cause of umbilical blood gas improvements induced by sitting delivery position is not directly due to the maternal blood gas difference, but may be mediated through other factors.