Occiput posterior position diagnosis: vaginal examination or intrapartum sonography? A clinical review

Abstract

The occiput posterior (OP) position is one of the most frequent malposition during labor. During the first stage of labor, the fetal head may stay in the OP position in 30% of the cases, but of these only 5-7% remains as such at time of delivery. The diagnosis of OP position in the second stage of labor is made difficult by the presence of the caput succedaneum or scalp hair, both of which may give some problem in the identification of fetal head sutures and fontanels and their location in relationship to maternal pelvic landmarks. The capability of diagnosing a fetus in OP position by digital examination has been extremely inaccurate, whereas an ultrasound approach, transabdominal, transperineal and transvaginal, has clearly shown its superior diagnostic accuracy. This is true not only for diagnosis of malpositions, detected in both first and second stage of labor, but also in cases of marked asynclitism.

Outcome of labor in vertex malposition in Cameroon

“…Our rate of VM in labor (5.3%) is lower than that of 10-30% reported elsewhere [3][4][5] , but that of persistent Occipito-Posterior (OP) position (89.2%) is higher than the rates of 1.8% to 10.8% found by others. 1,6,15 Because of low spontaneous rotation rate, our rate of persistent OP position at delivery (3.0%) is within the range of 1.8% to 6.0% found elsewhere.…”

“…[3][4][5] Risk factors for VM include nulliparity, maternal obesity, excessive fetal weight, pelvic (especially mid cavity) immaturity or abnormalities, epidural anesthesia and labor augmentation. 2,6,7 Diagnosis of OP position is done through a digital vaginal examination which finds the lambda fontanel towards the maternal sacrum.…”

“…6 Around 5-11% of cases of malposition persist till delivery. 1,3,5,11 Although instrumental vaginal deliveries are commoner in cases of VM, vacuum extraction is associated with higher failure rate than (Kielland's) forceps. 12,13 Manual rotation may correct the malposition.…”

Sonographic diagnosis of lateral asynclitism: a new subtype of fetal head malposition as a main determinant of early labor arrest

“…In most of these cases the option of proceeding to Cesarean delivery is considered despite failing to achieve a precise diagnosis of the underlying cause of dystocia. On the other hand, as previously reported also by our group for anterior asynclitism or face presentation, the use of ultrasound may assist the clinician in the exact diagnosis and the visual documentation of a malposition.…”

Randomised Italian Sonography for occiput POSition Trial Ante vacuum (R.I.S.POS.T.A.)

“…Over the past decades, several studies have demonstrated that clinical diagnosis of fetal head position by means of digital examination is highly inaccurate, particularly in cases of occiput posterior or occiput transverse position. On the other hand, evaluation of the fetal head position using transabdominal sonography (TAS), either during labor or before instrumental delivery, has proven to be far more accurate.…”