Hi Mrs B.
My SIL had this with her little girl born last year. She had an extra scan just to check that the baby was growing ok. But everything was fine. As far as I can rememebr the main implications are possible small baby and early labour. Neither of these things happened to SIL, her little girl was born a few days after her due date and weighed 7lb something.
Hope its a similar story for your mums cousins daughter xx