This topic will discuss the diagnosis, clinical course, and management of occiput transverse (OT) position. OT position is unrelated to transverse lie, in which the long axis of the fetal body is perpendicular to that of the mother.
Digital examination — The diagnosis of OT is generally based on findings from the transvaginal digital examination. The fetal sagittal suture and fontanelles are palpable in the transverse diameter of the pelvis. The fetal ears can be palpated superiorly under the symphysis and inferiorly above the sacrum/coccyx. If the occiput (posterior fontanelle) is on the mother's left side, the position is LOT; if the occiput (posterior fontanelle) is on the mother’s right side, the position is ROT.
Ultrasound examination — While digital vaginal examination of fetal position has been the accepted standard for diagnosis, there is evidence to suggest that ultrasound assessment of fetal position can be more consistent.Either transabdominal, transvaginal, or transperineal ultrasound can be employed, though at least one group reported greater success using a transvaginal approach. If ultrasound is used to determine fetal positon, the obstetric provider should receive specialized training for the procedure and undergo supervision by a more experienced diagnostician until he/shedevelops proficiency.
The key diagnostic feature for identification of OT position is the location of the fetal orbits. Both orbits are posterior when the fetus is occiput anterior (OA) and both are anterior when the fetus is occiput posterior (OP), whereas in OT position, one orbit is anterior and the other is posterior. If both orbits are on the maternal left, then the fetal position is ROT. If both orbits are on the maternal right, then the position is LOT.
Differential diagnosis — Anterior or posterior asynclitism, defined as rotation of the sagittal suture away from or toward the pubic symphysis, respectively, may result in misdiagnosis of OT as either occiput anterior or occiput posterior. Palpation of the fetal ears superiorly and inferiorly can help distinguish OT position from asynclitism. If the diagnosis is uncertain after careful physical assessment, ultrasound examination can be used to clarify the fetal position.