Fluid in sac

At my 6+2 US last week, my doctor mentioned something about the fluid in my sac. I sent a mychart msg asking for clarification and this was his response:

“I saw a "lacy" pattern in the fluid in her gestational sac which I sometimes seen. This is usually without incident, but it can be re-checked when she comes in next week."

Does anybody know anything about this? Is this a cause for concern? The scan otherwise looked great - measuring a day ahead with a heart rate of 143!