PitFalls in GFR: Pregnancy

A 29 year old pregnant female with a serum crt of 0.8mg/dl and eGFR of 90cc/min.
During Pregnancy, GFR increases by 40-65%, as a result, crt will fall and be lower than usual state of health in most part of pregnancy. 

Per studies, the MDRD formula underestimates the true GFR on the basis of inulin clearance by more than 40ml.min.  Another study found the bias to be less- around 20cc/min. There are currently no published data on the accuracy of the MDRD formula in pregnant subjects with GFR <60 ml/min. Given these issues, 24-h urine collection for CrCl remains the gold standard for GFR estimation in pregnancy. In the above case, it may reflect diminished renal function in the setting of pregnancy. 

Ref:
http://www.ncbi.nlm.nih.gov/pubmed/17970797
http://www.ncbi.nlm.nih.gov/pubmed/17909992