Station of the fetal presenting part. VI. Arrest of descent in nulliparas.

The specific labor aberration of arrest of descent was investigated in 253 nulliparas. It was found to be associated with fetopelvic disproportion in 52%. Delivery outcome was adversely affected by such factors as high fetal station at time of arrest and long duration of arrest. Arrest of descent occurring during the administration of oxytocin infusion was particularly ominous, no patient subsequently delivering vaginally. The best delivery prognosis was seen in those cases in which apparently causative inhibitory agents, including peridural anesthesia and sedation, were allowed to abate expectantly. Neither immediate operative delivery nor expectancy (other than in the specific abatement cases) was determined to be an appropriate approach to resolving this problem. Postarrest progression, especially if at a rate that was the same as or greater than prearrest descent, proved to be a favorable sign for delivery outcome. Neonatal depression and birth trauma were closely correlated with midforceps procedures, especially when done in conjunction with forceps rotation. Cephalopelvic disproportion yielded poor perinatal results, particularly among those delivered vaginally by instrumental means. Uterotonic stimulation of labor to correct the arrest problem therapeutically also had an adverse effect on the fetus when followed by operative delivery. Based on these observations a program of management was evolved for treating patients with arrest of descent.