Occipital posterior and occipital transverse positions: reappraisal of the obstetric risks

Abstract

Malpositions in labour in a vertex-presenting fetus are known to be associated with increased risks of operative delivery A retrospective analysis of all deliveries over 4 years in a university teaching obstetric unit was performed using the available obstetric database. All cases of live births with cephalic presenting babies after 36 completed gestational weeks were analysed, and included 17,533 out of 20,533 total deliveries over the study period. The study group included those cases with occipital posterior and transverse positions, based on the documentation of the position of the vertex at the time of delivery, or at the last clinical examination before obstetric intervention, while occipital anterior cases constituted the control group. The overall incidence of malpositions was 14%, and operative delivery rate in the study group was 82.5% versus 20.7% in the control group. After excluding cases of operative delivery for non-mechanical indications, such as fetal distress, the adjusted odds ratio for the malposition group was 9.8 (95% CI 8.91-10.8) for total assisted delivery and 30.2 (95% CI 25.6-35.5) for Caesarean section compared to the occipital anterior group. Malpositions are definitely associated with a marked increase in the risk of operative delivery including Caesarean section. Labour complicated by malposition should be considered high risk, and should warrant due preparation for obstetric intervention.

Outcome of labor in vertex malposition in Cameroon

“…1,4,6 Cephalopelvic disproportion (CPD) rate in our series (77.8%) was similar to the rate of 78% reported by some authors. 6 The diagnosis of CPD was done when the descent of the fetal head remained between 5/5 and 3/5 one hour after full cervical dilatation with irreducible overlapping of fetal head sutures.…”

“…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.…”

“…15 Even when vaginal deliveries occurred in the VM group, they needed more instrumental deliveries (RR 7.7), as noticed by some authors. 4,6 Our rate of instrumental vaginal deliveries (32.4%) was slightly higher than the rates of 24-26% observed by the same authors. This is explained by the fact that since the diameter of the presenting fetal head was bigger, the fetal head could be arrested in the maternal pelvis and could favor prolonged second stage.…”

“…[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.…”

Instrumental delivery and ultrasound : a multicentre randomised controlled trial of ultrasound assessment of the fetal head position versus standard care as an approach to prevent morbidity at instrumental delivery

“…2 Failure to identify a malposition (especially an occipito-posterior position) is one of the factors that increases the likelihood of failed instrumental delivery and neonatal trauma. [13][14][15][16][17][18][19] The fetal head position is diagnosed on vaginal examination by delineating the suture lines of the fetal skull and fontanelles; however, accurate clinical diagnosis can be unreliable, varying between 20 and 75%. [20][21][22][23][24][25][26][27][28][29] The use of abdominal ultrasound to enhance the diagnosis of the fetal head position has been described in a number of small studies, but only two have evaluated the role of ultrasound at instrumental delivery.…”