A patient with a previous classical (vertical) uterine incision caesarean section at 32 weeks is now 36 weeks pregnant. What is the MOST significant risk differentiating her from a woman with a previous low transverse caesarean section (LSCS)?

• A Risk of uterine rupture is 4–9% with trial of labour, occurring earlier in gestation and more often catastrophically ✓
• B Higher risk of placenta praevia in the current pregnancy
• C Absolute contraindication to any labour; rupture rate equals that of transverse incision
• D Higher wound infection risk only; rupture risk is equivalent to low transverse scar

Explanation

A classical (vertical corporeal) uterine incision carries a risk of uterine rupture of 4–9% in subsequent labour and importantly may rupture during pregnancy (even before onset of labour) and at earlier gestations (32–36 weeks). In contrast, a low transverse scar (LSCS) has a rupture risk of only ~0.5–0.8% in labour and does not typically rupture before labour. Classical caesarean sections are therefore considered a contraindication to trial of labour after caesarean (TOLAC), and elective repeat caesarean section at 36–37 weeks is recommended to pre-empt the risk of rupture before 39 weeks.

Reference: Williams Obstetrics, 26th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.