Yep I had the numbness in the leg with this pregnancy. I found that when I would lay on the left leg (coz that was the one to go numb) that I would awake to find it numb. So I tried laying on the right side. Only to have my groin ache like buggery. Mine got bad that I had to lay practically sitting up as the pain in the groin would hurt so much I could hardly lift my leg to get out of bed. I had what I believe was Pelvic Pain. Tell your sis inlaw to mention it to her OB or at her next check up. Just to be safe. It could be something a lot less simple than what I have.