CORRECTING FOR ETHNICITY WHEN DEFINING LARGE FOR GESTATIONAL-AGE INFANTS IN DIABETIC PREGNANCIES

The large-for-gestational-age (LGA) infant, defined as >90th birthweig ht percentile, is associated with mild disturbances of maternal glucos e tolerance. In the UK the same birthweight percentile charts are used for all ethnic groups when assessing LCA infants. The influence of ma ternal hyperglycaemia on LGA infants of Asian (Indian Sub-continent) m others in the UK is likely to be under-reported, as Asian birthweights tend to be lower than White/Europid birthweights. We assessed the num ber of LGA infants born consecutively to 21 Asian and 26 White/Europid mothers with gestational diabetes mellitus (GDM), delivered between 3 7 and 42 weeks gestation, and also in 34 Asian and 121 White/Europid m others with a positive screening test for GDM but a normal 75 g oral g lucose tolerance test (OGTT). Large-for-gestational-age infants were i dentified using both the standard UK percentile charts of the Medical Research Council and percentile charts constructed from 30418 Asian an d 162477 White/Europid singleton births, delivered between 37 and 42 w eeks gestation to non-diabetic mothers delivered in the North West Tha mes Region of England. The standard Medical Research Council percentil e charts, compared with the ethnically derived charts, identified fewe r LCA Asian (7/56 vs 15/56) but more White/Europid infants (33/147 vs 21/147). When correcting for ethnicity more Asian than White/Europid G DM mothers delivered LCA infants (9/21 vs 3/26, chi(2) = 4.76, P < 0.0 5). The maternal 2 h OGTT plasma glucose was a significant independent contributor to birthweight in the Asian (r(2) = 0.319, p < 0.0005) bu t not the White/Europid infants, in whom gestational age and maternal height were significant independent contributors to birthweight (r(2) = 0.158, p < 0.0001). We conclude that ethnic influences are important when defining LGA infants and that mild disturbances of maternal glyc aemia have a greater influence on the birthweight of Asian than White/ Europid infants.