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Persistent Fetal Occiput Posterior Position

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.

Obstetric Outcomes According to Position in Nulliparas and Multiparas Combined 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 Chorioamnionitis 1.1 4.7 <.001 Delivery type         Spontaneous 83.9 37.7     Assisted vaginal 9.4 24.6 <.001   Cesarean 6.6 37.7   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 *--N = 6,401 for overall length, 5,703 for length of first stage, and 5,293 for length of second stage of labor. Data are missing for the stages of labor because the time of full dilatation (onset of second stage) was not known. The number of women with data for second stage is also smaller because some women (n = 410) did not have a second stage, because they were delivered by cesarean before reaching full dilatation. Reprinted with permission from Ponkey SE, Cohen AP, Heffner LJ, Lieberman E. Persistent fetal occiput posterior position: obstetric outcomes. Obstet Gynecol 2003;101:917.

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.

ANNE D. WALLING, M.D.

Ponkey SE, et al. Persistent fetal occiput posterior position: obstetric outcomes. Obstet Gynecol May 2003;101:915-20.

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