Small yolk sac?

Stuuuaaart

I'm 36 and pregnant with my second child. I had my second sono today at 8 weeks. The sonogram was to determine the exact due date because the baby looked smaller than it should be in the first sono. I had some spotting Monday Tuesday and then again yesterday so I was nervous going in to this appointment. They said the baby grew from last week and was measuring on target and that the heart beat was good (174) but that the yolk sac may be small. Has anyone experienced this? I have a follow up in 2 weeks but I would like to hear stories if anyone has any to share. I looked this up online and found a bunch of negative relative results.