Why does the OB need to check the mum 6 weeks after delivery? Not to mention doing an IE.

This examination is crucial for the gynae to ensure that the stitches have more or less recovered and your body is "back to normal" or on the right track for recovery. This is especially so for women who have severe vaginal tears, complicated pregnancies/deliveries or c-sections where the risk of infection is higher if the stitches were not done well.