[Observations and considerations on fetal risk by umbilical cord entanglement]

Mean actual pH-values in umbilical arterial (UA) and venous (UV) blood as well as mean AV-pH-differences (AVD-pH) were computed for individual Apgar-scores (1 min) in a sample of 10,580 term neonates, which were born vaginally from vertex position. The newborns of the study group showed all different kinds of cord entanglements (CE, N = 3430); neonates without CE were used as controls (N = 7144). In addition infants of the study group were attributed to two different birth weight-centile groups: < 25. and > 75. percentile.

In the study group mean AVD-pH-values in individual Apgar-scores showed a significant (P < 10(-5)) increase when compared with controls. The numerical value of AVD-pH seems to be a function of the clinical condition of the newborn: maximum value (mean = 0.113) was reached at Apgar 7; increasing neonatal distress was accompanied by low AVD-pH-values. This phenomenon was due to a decrease of actual pH in UA-blood and an increase in UV-blood; the latter was statistically feasible (P = 0.025) only in neonates with Apgar 8. AVD-pH-values of neonates above the 75. weight-centile showed a different reaction-pattern in individual Apgar-scores when compared with infants below the 25. centile: They remain constant or are slightly increased. We concluded, that blood-flow reduction in the umbilical vessels leads to a flow-dependent improvement of fetal pCO2-excretion at the placental level, which counteracts the developing metabolic fetal acidosis.(ABSTRACT TRUNCATED AT 250 WORDS)