'Foetal lie' is the term which refers to the long axis of the foetus relative to the longitudinal axis of the uterus.

The 3 types of lie are:

• longitudinal lie (99.7% of foetuses at term)
• transverse lie (<0.3% of foetuses at term)
• oblique (<0.1% of foetuses at term)

The incidence of transverse lie is slightly higher than oblique lie. However, the causes and management options are the same for both. Oblique lie is easier to correct because the foetus is closer to longitudinal lie.

Transverse lie is an abnormal foetal presentation whereby the foetal longitudinal axis lies perpendicular to the long axis of the uterus. In real terms, this means the foetal head is on the lateral side of the pelvis and the buttocks are opposite. When in transverse lie, the foetus can be either 'scapulo-anterior' (most common) where the foetus faces towards the mother's back or 'scapulo-posterior' where the foetus faces towards the mothers front.

Epidemiology

• Early in gestation, transverse lie is very common. Most have moved to longitudinal lie by 32 weeks.
• At term, one in 300 foetuses are in transverse lie.

Risk factors:

• Most commonly occurs in women who have had previous pregnancies
• Fibroids and other pelvic tumours
• Pregnant with twins or triplets
• Prematurity
• Polyhydramnios
• Foetal abnormalities