I am 30 weeks pregnant and my baby has had slow growth also. At a 16 week scan she was approx. 2 weeks behind, 20 week scan showed 13 days behind, 26 week scan she was 8 days behind, now at 30 weeks she is in the lower range of average.

I cannot speak for twins or the HR however I was told that if anything her growth would slow more as my pregnany progressed, she is under fortnightly monitioring however she seems to be gaining weight at a great rate.

I hope this helps.

Good Luck.