...And how early can they start?
I never had any at all with DS but this time round (I am 20wks with DCDA twins) I have been getting mild period type pains a few times a day in my lower tummy/back. Generally it's when I have been sat at my desk for a long while without moving and stand up, or while I'm on the loo. They only last a few seconds then disappear.
Are these Braxton Hicks or is it just general muscle cramps/stretching?