What causes fetal macrosomia in gestational diabetes mellitus (GDM)?

Updated: Apr 29, 2020
  • Author: Thomas R Moore, MD; Chief Editor: George T Griffing, MD  more...
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Excess nutrient delivery to the fetus causes macrosomia and truncal fat deposition, but whether fasting or peak glucose values are more correlated with fetal overgrowth is less clear. Data from the Diabetes in Early Pregnancy project indicate that fetal birth weight correlates best with second- and third-trimester postprandial blood sugar levels and not with fasting or mean glucose levels. [37] When postprandial glucose values average 120 mg/dL or less, approximately 20% of infants can be expected to be macrosomic. When postprandial levels range as high as 160 mg/dL, macrosomia rates can reach 35%.

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