does the size of my baby depend on my diet?

I just got my ultrasound for 33 weeks mark done yesterday at 32+6 days. Baby was estimated at about 1.9 kilos (abt 4.2 pounds). Just a little under the average weight mark which is still of course ok...but I'm just wondering does it have to do with diet? I've gained already abt 30 pounds😓 and I am eating really healthy....