hi mommy, 1st scan usually between 8-12 weeks. better to go at 10week above so u can hear heartbeat and see baby. but if there's bleeding or any signs that make u feel uneasy can go early. 2nd trimester usually 16 week ish, depends too. not too sure if they allow for weekly scan, but usually if there are complications example threaten miscarriage they will follow up with you every 2 weeks.