Oblique Lie

Oblique lie is a fetus whose long axis lies at an angle of about 45 degrees to the long axis of the mother, with the head or breech in one iliac fossa. It is an unstable and transient lie, and it usually changes to a longitudinal lie in labour as the lower segment tightens. It matters because if it persists it becomes a shoulder presentation, with a high risk of cord prolapse and obstructed labour.

• Risk factors: grand multiparity, polyhydramnios, placenta previa, uterine fibroids or anomaly, prematurity, twin pregnancy.
• The presenting part is in an iliac fossa, not over the pelvic brim.
• Many convert spontaneously before or in early labour.

Women have an asymmetrical abdomen with the fundal height lower than dates, a head felt in one iliac fossa and the breech high on the other side, and an empty pelvis. Most have no symptoms.

• Uterus tilted to one side with the fetal heart heard in a flank.
• Presenting part not engaged.
• Differential diagnosis: transverse lie, unstable lie, breech presentation, twin pregnancy, placenta previa, uterine anomaly, fibroid.
• Complications: cord prolapse, conversion to shoulder presentation, obstructed labour, uterine rupture, fetal death, caesarean section, postpartum haemorrhage.

The diagnosis is made by abdominal palpation and confirmed by ultrasound.

• Abdominal examination: oblique axis with the presenting part in an iliac fossa, head and breech on opposite sides.
• Ultrasound: lie, placental site, liquor volume, fetal anomaly, uterine anomaly, fibroids or adnexal mass, estimated fetal weight.
• Cardiotocography; blood group and haemoglobin.
• Repeat scan at 36 to 37 weeks and at each visit to follow the lie.

The principle is to confirm the lie, exclude a cause, attempt external cephalic version if the lie persists at 36 to 37 weeks and admit when labour starts, with caesarean section if the lie does not correct.

• Supportive: avoid vaginal examination until placenta previa is excluded; advise to attend at once for contractions, leaking fluid or bleeding. Admit at 37 weeks if a grand multipara or living far from the facility; in labour, position the mother on the side of the head and use abdominal binders only under supervision; group and cross-match in labour.
• Pharmacological:
  • Terbutaline 0.25 mg subcutaneous once, 15 minutes before external cephalic version.
  • Anti-D immunoglobulin 500 IU IM within 72 hours after version for RhD negative women.
  • Oxytocin 10 IU in 1 litre Ringer's lactate (10 mU/mL) started at 12 mL per hour (2 mU/minute) and doubled every 30 minutes to a maximum of 192 mL per hour (32 mU/minute). Use only for stabilising induction once the lie is longitudinal, with the head held over the pelvis, senior review and never in a scarred uterus.
  • Cefazolin 2 g IV as a single dose before caesarean section.
  • Oxytocin 10 IU IM after birth, then 20 IU in 1 litre at 125 mL per hour for 4 hours.
• Procedures:
  • External cephalic version at 36 to 37 weeks in a theatre capable facility (contraindicated by placenta previa, recent bleeding, abnormal tracing and ruptured membranes).
  • Stabilising induction with amniotomy after correction of the lie to a longitudinal lie at 38 to 39 weeks, with the head held over the pelvis and continuous cardiotocography.
  • Planned caesarean section at 38 to 39 weeks if the lie persists.
  • Emergency caesarean section for rupture of membranes with a non longitudinal lie, cord prolapse or bleeding.
• Special groups: preterm oblique lie before 34 weeks is observed because most convert; a uterine scar has caesarean section instead of stabilising induction.
• Red flags: contractions, leaking fluid, bleeding, cord prolapse, reduced fetal movements, shoulder or arm felt in the vagina.
• Follow-up: weekly review from 36 weeks with a scan for lie; newborn examination; counselling that the next birth should be in a facility.