Serum Creatinine in Pregnancy: A Systematic Review

Area of Science:

• Nephrology
• Obstetrics
• Clinical Chemistry

Background:

• Standard assessment of renal function in pregnancy relies on serum creatinine.
• Established normal gestational ranges for serum creatinine are lacking.
• Accurate ranges are needed to identify abnormal kidney function during pregnancy.

Purpose of the Study:

• To systematically review and define serum creatinine concentrations in healthy pregnancies.
• To compare pregnant women's serum creatinine levels with those of nonpregnant women.
• To establish reference ranges for identifying abnormal kidney function in pregnancy.

Main Methods:

• Systematic review of Medline, PubMed, Embase, Web of Science, theses, and obstetric texts up to July 2017.
• Included studies quantified serum creatinine in pregnant cohorts with local ranges or matched nonpregnant cohorts.
• Analyzed mean and upper reference limits for creatinine, expressed as pregnant:nonpregnant ratios, using meta-regression for heterogeneity.

Main Results:

• Data synthesized from 49 studies involving 4421 serum creatinine values.
• Mean serum creatinine in pregnancy was 84% (1st trimester), 77% (2nd trimester), and 80% (3rd trimester) of nonpregnant means.
• Upper limits (97.5th centile) were 85%, 80%, and 86% of nonpregnant upper limits across trimesters.

Conclusions:

• A serum creatinine level >77 micromol/l (0.87 mg/dl) is considered abnormal in pregnancy, based on a nonpregnant range of 45-90 micromol/l.
• This defined upper limit aids in identifying potentially compromised kidney function during gestation.
• Future research can correlate these serum creatinine values with adverse pregnancy outcomes.