Influence of occiput posterior position on the fetal heart rate pattern.

Fetal heart rate (FHR) recordings of 138 deliveries with the fetus in the occiput posterior position (OPP) are compared with recordings of 138 control fetuses in the occiput anterior position (OAP). The 2 groups are comparable in maternal age, parity, duration of first stage of labor, frequency of nerve blocks for analgesia, and incidence of cord complications. Variable decelerations were significantly more frequent and more pronounced in the OPP group than in the controls. The number of newborns with low Apgar scores was similar in both groups, despite a large number of pronounced decelerations in the OPP group. Possible mechanisms for the origin of variable decelerations in the occiput posterior position are discussed.