[Birth asphyxia - an unsolved problem of perinatal medicine]

Birth asphyxia is defined as a severe disturbance of oxygen supply to the fetus, which develops during the first or second stage of labor. The diagnosis is confirmed by a severe metabolic acidosis in the umbilical cord blood, a persistent low Apgar as well as functional disturbances as a result of hypoxic damage in various organs including the central nervous system. Apart from morbidity and mortality in the neonatal phase long term effects are of considerable significance. Only 10 - 15 % of all cerebral palsy cases developing after delivery at term are a consequence of a hypoxic encephalopathy developing during the process of labor and delivery. For a long time it was ignored, that a number of pregnancy pathologies may lead to brain damage, which could also produce the typical symptoms of cerebral palsy. An abrupt disturbance of oxygen supply may be a result of cord compression, a premature separation of the placenta or of rupture of the uterus. These situations are in general easily recognized by typical clinical symptoms together with a sudden drop in fetal heart rate with a persistent bradycardia. In these cases it is only possible to prevent hypoxic brain damage, if the fetus can be delivered by emergency caesarian section within 15 - 20 minutes after the acute event. Diagnosis and evaluation of subacute or chronic forms of insufficient supply of oxygen of the fetus in labor is considerably more difficult. Reliability of continuous heart rate monitoring of the fetus during labor as well as validity of certain heart rate changes for the detection of developing hypoxia is a matter of ongoing dispute. In the presence of clearly pathological heart rate patterns hypoxic damage may already have occurred. Suspicious or "non-reassuring" heart rate alterations are frequent and only in a small percentage a real threat to the fetus in form of severe hypoxia will develop. Up until now there is no clear scientific proof that a combination of continuous fetal heart rate monitoring with additional tests can prevent hypoxic damage to the fetus. Future efforts should be directed towards improving reliability of the description of fetal heart rate patterns, the validity of the information provided by heart rate changes as well as the proof of the benefit of continuous monitoring of the fetus during labor and delivery as a means of preventing severe hypoxia and its consequences to fetal health.