[Evolution promotes a minimal effect of fetal labor stress during birth]

Controlled labor-caused fetal stress during birth can be tolerated better than generally suspected. This is the result of a pilot study among 1000 term infants in which the postpartum development of neonate weight was evaluated as a simple parameter of adaptation to extrauterine life. I. The clinical relevance of postpartum weight development was demonstrated in newborns whose mothers had been hospitalized during pregnancy e.g. because of hyperemesis, diabetes or gestosis. Postpartum these newborns showed longer lasting and more extensive weight loss. II. On the contrary moderate fetal stress during labor results in less and shorter lasting weight loss of the newborn term infants born after a labor-period of 12 hours showed a weight loss greater than 5% of their birth weight. Only half as often as newborns after a shorter period of labor. Further parameters of stress like a 1 minute APGAR score up to 6 versus 1 minute APGAR between 8 and 10 or umbilical cord ph-values below and over 7.20 revealed the same tendency. Newborns with green amniotic fluid (as a sign of stress) during birth also had a lower weight loss (up to 2% of birth weight) twice as often as newborns without green amniotic fluid. A statistically significant relation was also seen between the way of delivery as another aspect of stress and postpartum weight: on the 5th day postpartum newborns delivered by cesarean section showed a weight below birth weight three times as often as babies delivered by vaginal-operation means. The evolutionary aspect of catecholamine-peak during birth as protection against labor-induced hypoxemia and as advancing factor of adaptation to extrauterine life makes the results of this study seem plausible. This topic deserves more clinical research.