Baby's HC measuring small

hi all, i recently had my ultrasound scan at 31+4 weeks. during the scan, i saw that my baby's HC (head circumference) was about 30 weeks but doctor said that everything looks good. she later then scheduled another detailed scan at my 34 weeks (so far already did 2 detailed scan) abit worried now since i have GDM and also dealing with high BP. any mummies with GDM too that had to do 3 detailed scan? and should i be worried about baby's head measuring smaller? #pleasehelp #advicepls