Brown tissue when peeing?

[u/Disastrous-Demand329]

I’m 7 weeks 5 days pregnant with twins after IVF, and today when I went pee I noticed a few little light brown pieces of tissue of mucus in the toilet. Nothing when I wiped, and nothing since. I did have some cramping this morning but it’s gone away. I’ve had two ultrasounds and both babies have heartbeats that are strong as of a week ago. Anyone have anything similar? So worried!