Abstract
Maternal and fetal acid-base changes in a series of 56 normal cases from Edmonton, Canada, are compared with a similar series from Lund, Sweden, published by Jacobson. During labour, pH in the mother and in the fetus falls in Lund, but not in Edmonton. The mothers labour hard in Lund and are more sedated in Edmonton. The pH difference (δpH) between the maternal and fetal blood is about 0.10 in both series.
In another series of 61 cases classified as abnormal because of changes in fetal heart rate or meconium staining of the amniotic fluid, the mean δpH was 0.15. δpH was correlated to the fetal scalp pO2 and oxygen saturation and there was a significant drop in fetal oxygenation when ≤pH increased.
It is suggested that fetal preacidosis be redefined as δpH 0.15–0.19 and acidosis δpH≤0.20 pH units.