RESUMO
The purpose of this review is to summarize the available evidence on occipito-posterior fetal head position and maternal and neonatal outcome. The occipito-posterior fetal head position is the most common malposition, but there are not so many data about it in literature. Its incidence is ranging from 1.8% by Fitzpatrick, to 4.6% and 5.5% by Yancey and Sizer, to 6% by Ponkey. Only two trials studied the occipito-posterior associated factors. There are lower incidence of premature rupture of membrane, arterial hypertension pregnancy-induced, induced labour, increased of episiotomy, instrumental delivery and a decreased of vaginal birth without a difference in neonatal Apgar, and with a neonatal bigger weight. The occipito-posterior fetal head position persistence compared to anterior position, has a statistically significant association with low maternal stature, previous cesarean section, longer first and second stage of labour, oxytocin augmentation, epidural analgesia, instrumental vaginal delivery, chorion-amniositis, vaginal perineal injures, loss of blood and post partum infections. A highest incidence of occipito-posterior fetal head position may depend by nulliparity, malnutrition with pelvic deformity, pelvic immaturity in the teenager and anterior placenta. Epidural analgesia is a risk factor for fetal head malposition. The majority of occipito-posterior fetal head positions is not due to a malrotation, but to a persistence in this position of the fetal head. In fact, this persistence leads to a failure of the fetal head rotation. The prolonged second stage is often the result of occipito-posterior fetal head position and instrumental delivery is required. The traditional vaginal examination is not useful for the determination of fetal head position, so and instrumental method is needed, such as ultrasound, for a correct evaluation of fetal head position, particularly if a vaginal instrumental delivery is necessary. This is recommended by the Canadian Society of Obstetrics and Gynecology. The evaluation of fetal head position is important in the prediction of labour induction.
