Edwards (T18) and Patau's (T13) testing

Has anyone been told their bloods were too low to check for Edwards (T18) and Patau's (T13) Syndromes? I had mine done Monday at my scan, when she done the scan part to check, she it all looked perfectly normal.

The lady that did my bloods just called, and said the blood needs to be at 45 or above for them to be able to check it, but mine was slightly lower at like 44 point something, so literally just under, but they won’t check my bloods because of that.

She said I need to go in for another scan to check, instead of taking blood again, and the people that check the blood will accept an up to date scan instead of bloods.

I asked if it was anything to worry about because the scan was perfect & she was growing ahead by 3 days, but she said it’s nothing to worry about. I’m hoping it’s just a case of them needing an up to date scan, as nothing flagged up on Monday. I’m trying not to worry as the scan on Monday was perfect.

She didn’t seem concerned my bloods were low, so I don’t know if my bloods are low in general and it needs looking into, my bloods were fine at the tests I had done with the midwife at the beginning of June, or if it’s just my bloods were low for their testing.