Are we missing at-risk babies? Comparison of customised growth charts v. standard population charts in a diabetic population
Background. Diabetes in pregnancy is associated with both accelerated fetal growth and intrauterine growth restriction.
Objective. To compare the difference in occurrence of large-for-gestational-age (LGA) and small-for-gestational-age (SGA) fetuses in a pregnant diabetic population using population-based growth charts and customised growth charts.
Methods. Retrospective observational study at Steve Biko Academic and Kalafong hospitals, Pretoria, South Africa. Information from an electronic database was used to retrospectively generate customised centiles using a web-based tool (www.gestation.net). The first fetal growth scan of the third trimester, as determined by ultrasound, was plotted for each patient on both the population-based and customised growth charts. We compared the growth category on the population-based growth chart with that on the customised growth chart.
Results. Of the patients, 44 had type 1, 66 type 2 and 173 gestational diabetes. The growth of 79/283 fetuses would have been reclassified had customised growth charts been used. Of cases in which fetal growth was classified as appropriate for gestation on the populationbased growth charts, 58 fetuses would have been LGA and 14 SGA had customised growth charts been used. Four of the fetuses that were SGA and three that were LGA on the population-based growth charts would have been classified as appropriately grown on the customised growth charts. This was a statistically significant difference (p<0.001), with a Cohen’s kappa of 0.45 indicating moderate agreement.
Conclusions. Customised growth charts identified more babies with aberrations of growth, who may need vigilant antenatal care and elective delivery and may be at increased health risk in the future.