Although an estimated 5 percent of term cephalic singleton deliveries are in the persistent occiput posterior position, the outcomes and morbidity associated with this position are unclear. Ponkey and colleagues studied deliveries occurring in 1998 at a Boston teaching hospital to establish the labor outcomes associated with this fetal position.
They analyzed data from all term vertex singleton deliveries occurring in the hospital in 1998. After excluding cases complicated by diabetes mellitus, polyhydramnios, oligohydramnios, uterine abnormalities, intrauterine growth restriction, or death, the study comprised 6,074 occiput anterior and 360 occiput posterior deliveries. The data collected included maternal demographics, obstetric history, details of the current pregnancy and delivery, and pregnancy outcomes.
The overall rate of occiput posterior deliveries was 5.5 percent, but the proportion was nearly twice as high in nulliparas (7.2 percent) compared with multiparas (4 percent). Women with occiput anterior and posterior positions were similar in most variables, but those with posterior positions tended to be shorter and less likely to have Medicaid insurance. Mothers with occiput posterior position were more likely to have induced labors, but this increase was not significant (see the accompanying table). Conversely, most complications of labor were significantly more common in occiput position. Approximately one half of cases with occiput posterior position had prolonged first or second stages of labor and oxytocin induction. One fourth had assisted vaginal delivery, and more than one third had cesarean deliveries. The only negative outcome that was not increased significantly in occiput posterior positions was endometritis. The infants were similar in gestational age and birth weight. Low initial Apgar scores were significantly more common in the occiput posterior group, but scores at five minutes were comparable.
|Outcomes||Occiput anterior (n = 6,074)||Occiput posterior (n = 360)||P value|
|Induced labor (%)||31.1||35.8||.06|
|Length of labor > 12 hours (%)*||26.2||49.7||<.001|
|Length of stage 1 > 10 hours||30.3||48.3||<.001|
|Length of stage 2 > 2 hours||18.1||53.3||<.001|
|Oxytocin augmentation (%)||36.8||48.9||<.001|
|Epidural analgesia (%)||73.1||86.1||<.001|
|Delivery type (%)|
|Third- or fourth-degree tear (%)||6.7||18.2||<.001|
|Excessive blood loss (%)||9.9||13.6||.03|
|Postpartum infection (%)||0.8||2.2||.01|
|Gestational age (week)||39.4||39.4||.5|
|Male infant (%)||51.1||56.4||.05|
|Apgar, 1 minute (%)|
|0 to 6||7.1||12.4||<.001|
|7 to 10||92.9||87.6||—|
|Apgar, 5 minutes (%)|
|0 to 6||0.9||0.6||>.999|
|7 to 10||99.2||99.4||—|
|Shoulder dystocia (%)||2.1||0.8||.1|
|Nuchal cord (%)||21.6||18.6||.2|
|Birth weight (g)||3,504||3,492||.6|
The authors conclude that persistent occiput posterior position is associated with a higher rate of most complications of labor and delivery. Only one in four nulliparous women and just over one half of multiparous women with this presentation achieve a spontaneous vaginal delivery.