Sudden hyperflexion of thigh over abdomen (Mc Roberts manoeuvre) with of the following nerve is commonly involved?

McRoberts’ manoeuvre consists of forcible abduction of patients legs by sharply flexing them on the abdomen. It is the single most effective manoeuvre and should be the first manoeuvre to be performed in case of shoulder dystocia. McRobert’s manoeuvre results in straightening of the sacrum relative to the lumbar vertebra along with rotation of symphysis pubis towards the maternal head and it decreases the angle of pelvic inclination. Sometimes, over zealous use of McRobert’s manoeuvre may result in separation of the maternal pubic symphysis and injury to lateral cutaneous nerve of thigh.