My son, now 21 months did the Cadiff Half, the Tour of Torfaen, The Sodbury Slog, The Pembrey Multi Terrain 10 and the Lliswerry 8. The only effects seem to be that he is blimmin active !
The wife didn't know she was in the club for the first 3 of those races and ran them full steam. She ran (albeit didn't race) right the way thru her pregnancy right up until her waters broke.
My instinct though would be that nothing too strenuous ?