Girls, who had something like this yesterday was at ultrasound at 30 w…

Girls, who had something like this yesterday was at ultrasound at 30 weeks and 6 days, and the belly circumference of the baby corresponds to 30 weeks and 3 days. Weight by ultrasound is 1480, they put a small fetus and ultrasound control in 2 weeks. In 2 weeks she gained 120 grams. What could it be? Could it be that she's just small on her own?