The bearing-down efforts and their effects on fetal heart rate, oxygenation and acid base balance.

1. C l i n i c a l m a t e r i a l . The study was performed in 12 primigravidas, with uncomplicated pregnancies in which labor started spontaneously at term. Membranes ruptured spontaneously after cervical dilatation had progressed beyond 6 cm, usually with füll cervical dilatation (1). The fetus was single, in cephalic presentation. Cephalo-pelvic disproportion was discarded. All the newly born infants were in good condition. Their follow-up continues; their present age ranges between l and 8 months.