Measurements of fetal head compression pressure during bearing down and their relationship to the condition of the newborn.

Fetal head compression pressure (FHCP) and its clinical importance has been investigated in a group of 46 spontaneous births. Measurement of FHCP was facilitated using a compression transducer positioned between the fetal head and the wall of the birth canal. This method not only constitutes a means of quantitating the forces acting directly on the fetal head, but also provides information about the intracranial pressure generated during delivery. The latter extrapolation is based on the principle of applanation. The technique provides an objective and reliable estimate of intracranial strain and therefore a means of comparing the forces generated under different delivery modes. The condition of the same neonates at birth was assessed using umbilical artery pH, Apgar score, neurobehavioral testing and fundoscopic examination. The mean amplitude of FHCP in the different deliveries ranged from 38 to 390 mmHg (5-52 kPa) with an overall mean of 157.9 mmHg (21.1 kPa). The study indicated that the appearance of retinal hemorrhages in the newborn cannot be explained by exposure of the fetal head to abnormally high compression during birth. Other explanations must be sought for infants with a neurobehavioral deficit, reduced Apgar score, or umbilical artery acidosis at birth. It is concluded that a relatively short period of high FHCP has no obvious consequences for fetal well-being, at least within the limits described in the present report.