I'm 20 weeks with #2 and just had my 20 week ultrasound yesterday. The doctor mentioned that I had a good size placental lake (a mass of blood) and that these can be indicators of intrauterine growth restriction in the 3rd trimester but are typically not of concern in patients who have not had prior C-sections or D&Cs, etc. (I have not), but he did recommend I come back for another ultrasound in the 3rd trimester to check on everything. From what I read online, they sound like fairly common findings on ultrasounds nowadays because of better technology and are rarely an issue. Anyone else see a placental lake on their ultrasound?