37 weeks is fairly advanced pregnancy. Not much time is left after that. We expect baby to gain about 500 gm in the next 3 weeks, provided the placental function is normal. This diagnosis must be from Ultrasound. They would also have done Doppler study. So more important aspect is that if baby is growth retarded because of placental compromise,  then we should try to get the baby out of the hostile environment. Baby will flourish better outside .

Not much time left But definitely adequate rest , high protein diet , some supplements wil help .