How is fetal growth assessed 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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Monitoring fetal growth continues to be a challenging and imprecise process. Although currently available tools (serial plotting of fetal growth parameters based on ultrasonographic measurement) are superior to those used previously for clinical estimations, accuracy is still only within ±15%. [98]

In the obese fetus, the inaccuracies are further magnified. In 1992, Bernstein and Catalano reported that significant correlation exists between the degree of error in the ultrasonogram-based estimation of fetal weight and the percentage of body fat on the fetus. [99] Perhaps this is the reason no single formula has proven to be adequate in identifying a macrosomic fetus with certainty.

Despite problems with accuracy, ultrasonogram-based estimations of fetal size have become the standard of care. Estimate fetal size once or twice at least 3 weeks apart in order to establish a trend. Time the last examination to be at 36-37 weeks' gestation or as close to the planned delivery date as possible.

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