Yet Another reason to avoid an epidural...

Obstet Gynecol. 2005 May;105(5):974-82. Related Articles, Links

Changes in fetal position during labor and their association with
epidural analgesia.

Lieberman E, Davidson K, Lee-Parritz A, Shearer E.

Departments of Obstetrics and Gynecology, Brigham and Women's
Hospital, Harvard Medical School, and Boston Medical Center, Boston,
Massachusetts.

OBJECTIVE: To evaluate whether epidural analgesia is associated with a
higher rate of abnormal fetal head position at delivery. METHODS: We
conducted a prospective cohort study of 1,562 women to evaluate changes
in fetal position during labor by using serial ultrasound examinations.
Ultrasound examinations were performed at enrollment, epidural
administration, 4 hours after the initial ultrasonography if epidural
had not been administered, and late in labor ( 8 cm). Information about
fetal head position at delivery was obtained from the provider. RESULTS:
Regardless of fetal head position at enrollment (occiput transverse,
occiput posterior, or occiput anterior), most fetuses were occiput
anterior at delivery (enrollment position: occiput transverse 78%,
occiput posterior 80%, occiput anterior 83%, P = .1). Final fetal
position was established close to delivery. Of fetuses that were occiput
posterior late in labor, only 20.7% were occiput posterior at delivery.
Changes in fetal head position were common, and 36% of women had an
occiput posterior fetus on at least one ultrasound examination. Women
receiving epidural did not have more occiput posterior fetuses at the
enrollment (23.4% epidural versus 26.0 no epidural, P = .9) or the
epidural/4-hour ultrasound examination (24.9% epidural, 28.3% no
epidural), but did have more occiput posterior fetuses at delivery
(12.9% epidural versus 3.3% no epidural, P = .002); the association
remained in a multivariate model (adjusted odds ratio 4.0, 95%
confidence interval 1.4-11.1). CONCLUSION: Fetal position changes are
common during labor, with the final fetal position established close to
delivery. Our demonstration of a strong association of epidural with
fetal occiput posterior position at delivery represents a mechanism that
may contribute to the lower rate of spontaneous vaginal delivery
consistently observed with epidural. LEVEL OF EVIDENCE: II-2.