Measurement of head compression during labor: preliminary results.

To study the pressure to which the fetal head is exposed during the second stage of labor, an instrument was designed to measure continuously the pressure between the presenting part and the birth canal on both sides of the fetal head. Pressure parameters during and between the uterine contractions were calculated from 42 spontaneous vertex deliveries presenting as occiput anterior. During the second stage the overall average of the mean maximum head pressure during uterine contraction was 31.8 +/- 11.0 kPa, that of the mean head pressure measured 13.3 +/- 4.8 kPa during uterine contraction and 5.5 +/- 3.7 kPa during the interval between contractions. The pressure on the fetal head was about twice as high as the amniotic pressure. It increased towards the end of labor. The objective measurement of fetal head pressure is the prerequisite in the study of the relationship between birth-related injuries and excessive head compression during parturition.