What problems arise from having a fibroid during pregnancy? And what does it mean to have a prominent area behind the placenta?

I can answer part one of your question. During a pregnancy the fibroids shrink and can disappear. That is what my OB/GYN specialist told me with my second pregnancy and that is what happened. However, mine did grow back after a year.

Part two of your question - it could be a membrane. I would ask my doctor as to avoid any speculation.