Something blocking the baby on ultrasound?

Unique • Baby #2 11-3-23 ❤️

So I had an ultrasound today at 11 weeks 3 days. We couldn’t see the baby because something was “shadowing” over it. The baby heart rate was great at 140 and was able to see some movement. What could be blocking us from seeing the baby on the ultrasound? Has anyone had this before?