Double placenta?!

HazelRose626
I had my son 3 weeks ago just one baby, when I delivered my doctor was talking about my placenta and had the nurse save it to send for testing or something, I wasn't paying too much attention but when she came to check on me the next day I asked about it, she said the placenta is like a circle, and the umbilical cord attaches to the center, well I had two circles, that where attached I'm the middle by a thin membrane. She said it could have been an early twin but obviously at my 8 week ultrasound there was just my one baby. I did go in a 5 weeks because I had a little spotting and cramps on just one side. Anyways, what do you guys think? I see her again in 3 weeks for my postpartum checkup but I was just wondering why I had a weird alien placenta lol