Taking sneakpeek at 18 weeks?

Basically they pushed my ultrasound date till the ending of next month past when their suppose to do it because they're going off my original due date rather than my adjusted one its nearly at 23 weeks. So i ordered the test just to see what'll come out. I know if contamination occurs it could say boy and usually if it says girl then its definitely a girl. But would being 18 weeks make the results any more accurate?

So i told my husband if it says boy then to take it with a grain of salt and we'll just wait till our ultrasound that ill most likely be going to alone because of the virus. But that if it says girl then its most likely a girl? Good way of thinking?