I'm going to schedule a pregnancy ultrasound, my vet likes to do them at 30 days. Because of my schedule I can have the ultrasound on day 28 or day 32. I know it's not critical and an embryo count is usually not accurate but if my girls is prego's which day will give me a better assessment for litter size?

I would do day 32 if I were you. Good luck and let us know either way!

If you are only looking for litter size, than don't do a sonogram at all. Wait till close to whelp date, and xray. Much more accurate count than sono. I only do a sonogram to confirm pregnancy when there is a reason I will need to know before it is obvious, such as a show closing date, etc.

Why not a relaxin test? It is fast and fairly accurate. The faster and darker the second line, the bigger the litter - go with 32 days

I like to wait for day 32. Better chance of seeing more. Good luck.

Another vote for 32.