Is Having Small Placental Lake With Fetus Measuring In 52nd Percentile A Cause For Concern?

I am 20wks 3days pregnant with my second child (my first child was delivered via C-section at 35 wks due to being breach...not sure what caused early labor...I assume it was my extreme swelling) I delivered my first in June of 2013. Today at my u/s I was told I have a small placental lake, but not to be alarmed bc my baby is measuring in the 52nd percentile. I go back for an u/s to monitor the lakes at 28wks. I haven t found a lot of informational web pages regarding this issue. Can you help? What do dr s typically do if the lakes grow larger and cause a decrease or hault in fetal development?