Carlan S J, Wyble L, Lense J, Mastrogiannis D S, Parsons M T
Department of Obstetrics and Gynecology, University of South Florida, College of Medicine, Tampa 33606.
J Perinatol. 1991 Jun;11(2):105-11.
Head molding refers to changes in cranial bone relationships that occur in response to external compression force. In the normal term labor with vertex presentation, the suboccipito-bregmatic diameter shortens and the mentovertical diameter lengthens. This is accomplished partially through the unbending or straightening of the parietal bones rather than the frequently taught mechanism of overlapping sutures. The occipital and frontal bones may also contribute by an inward movement of their apex, using their basal portions as a hinge. A locking mechanism may occur in protracted labors as the free edges of the cranial bones are forced into one another, preventing further molding and providing more protection for the fetal brain. The preterm skull has weaker material properties and wider sutures. Thus, more molding at lower pressures is possible and the protective effect of "locking" may not be operational. A case of extreme antenatal preterm fetal head molding discovered at ultrasound is presented as an introduction to review the literature regarding molding.
头颅塑形是指颅骨关系因外部压力而发生的变化。在枕先露的足月正常分娩中，枕下前囟径缩短，颏顶径延长。这部分是通过顶骨的伸直或变直来实现的，而不是通常所讲的缝线重叠机制。枕骨和额骨也可能通过其顶端向内移动，以其基部为铰链来发挥作用。在产程延长时，颅骨的游离边缘相互挤压，可能会出现一种锁定机制，阻止进一步塑形，为胎儿大脑提供更多保护。早产胎儿的颅骨材料特性较弱，缝线较宽。因此，在较低压力下可能会有更多塑形，“锁定”的保护作用可能无法发挥。本文介绍了一例超声检查发现的产前极端早产胎儿头颅塑形病例，以回顾有关塑形的文献。
