the reason why there is a range is also depends on your baby’s position during the scan. sometimes the doctor cant do detail scan if the position tak ideal so you need to come again. you can go anytime around that range but no more than 24w.
i went last saturday at around 21w 6d, baby punya position agak menonggeng dalam tu jadi sonographer cakap susah sikit nak scan angle dia but check² semua ok.
I baru buat anatomy scan last week. 20weeks. Just pick in the middle to be safe