Effects on Head Form of Intrauterine Compression and Passage Through the Birth Canal

Abstract

During birth the infant’s head is exposed to contractions of the uterine muscles and to intra-abdominal pressure. These mechanical influences are the cause of transitory physiological or enduring pathological changes on the skull. The exact effect of the uterus on the skull in utero is not fully understood. Studies on head molding during labor have been based mainly on x-rays.⁴ Moloy concluded from x-rays taken as early as 1 hour after birth that the infant’s head was usually not deformed during normal labor. He also observed, however, a dislocation of the parietal bones resulting from pelvic narrowness. Borell and Fernström^2,3 examined radi-ologically the deformation of heads in 27 newborn children during normal and pathological births, observing that skull deformaties differ according to the size of the pelvic opening. Therefore, the developmental dynamics of skull form at birth are a result of the relative volumes of the fetus’ skull and the parturient’s pelvis, relative to the birth presentation.