There are manual stretching exercises you can do, or get your dh to help. I have some diagrams on how to do them but i never got around to it and i had a 2nd degree tear to so i wish i did and will be doing them throughout the pregnancy this time - maybe try a google search as i'm not sure where i got this pamphlet from.
Also if you find the scar tissue is still tender or uncomfortable you can have a pessary treatment which somehow heals it. I did this as mine was still too painful to touch after 11 months, after the treatment it was fine.
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