The 18-20 wk scan is the one they like you to have.

Any earlier cans are normally only done for dating, spotting etc, or the 12 week one for downs syndrome screening.

I had the 12 week one (public patient, MIA at public hospital), my doctor asked if I wanted it or not & referred me. It cost $100 and was not claimable on medicare.

All my other scans where I was referred have had a medicare rebate (6, 19 and 36 weeks)