抄録
Six hundred and eighty nine newborns were studied in order to better elucidate the mechanisms causing the deformity of the head of infants at birth. Measurements of the infants head was carried out immediately after birth and every day theraf ter, up to the 6 th day. Measurement of the fetal head was carried out by x-ray and ultrasonic method.
1. The biparietal diameter of the infants' head measured by ultrasonic and x-ray methods gave a correlation coefficient of r=+0.920.
2. Any deformity in the infants' head at birth was repaired around the third postpartum day.
3. In the pelvis with a flat sacrum, there was pronounced shortening of the circumference around the suboccipitobregmatic diameter of the infants head. There was marked shortening of anterior-posterior diameter of the infants head noted in the pelvis with a flat entrance.
4. When the difference between the shortest anteriorposterior diameter of the pelvis and largest transverse diameter of the infants head is less than 1 cm, or the difference between the anterior-posterior diameter of the wides part of the pelvis and biparietal diameter of the infants head is less than 2 cm, or that the distance between the spina ischiadica of the pelvis and largest diameter of the infants' head is less than 0.5 cm, the largest transverse diameter of the infants' head is markedly shortened at birth.
5. The moulding of the infant's head delivered from a pelvic position is less than that delivered from a head presentation.
6. The moulding of the head of the first born child is more than that of second or later infants.
7. Deformity of the infant's head tends to be greater in deliveries requiring more than 20 hours than in those requiring less than 8 hours.
These observations would indicate that the deformity of the infant's head at birth is mainly due to the resistance of the bony and soft birth canal and not due to the resistance of the infant's head itself.
