Relationship of Fetal Macrosomia to a 75g Glucose Challenge Test in Nondiabetic Pregnant Women

Summary: We determined in nondiabetic women, the relationship of plasma glucose values obtained 2 hours after a 75 g oral glucose challenge test (GCT) at 16–20 weeks' gestation, with the incidence of macrosomia in term deliveries (37–41 weeks' gestation). From 1988–1990, in a systematic screening programme data collected prospectively from 1,331 women were analysed retrospectively. Women with gestational diabetes or impaired glucose tolerance (n = 53) were excluded. The rest (n = 1,278) had no evidence of glucose intolerance including 1,215 women with normal plasma glucose by GCT (< 7.8 mmol/L 2 hours after 75 g oral glucose load) and 63 women with abnormal GCT but no abnormal value at a glucose tolerance test. The GCT values were divided into 5 groups: Group A (< 4.5 mmol/L), B (4.5-5.5 mmol/L), C (5.6-6.6 mmol/L), D (6.7-7.7 mmol/L) and E (> 7.8 mmol/L). The variables studied were age, parity, gestational age at delivery and incidence of macrosomia.
Using <4 kg birth-weight as the definition of macrosomia, the incidence increased from 1.2% to 9.5% with increasing plasma glucose values in the GCT from Group A (< 4.5 mmol/L) to E(> 7.8 mmol/L). Similar trends of increasing incidences from 7.2% to 15.8% and 2.9% to 9.5% were noted when 90th and 95th birth-weight percentiles, respectively were used as definitions of macrosomia. The test of linear trend in this association was significant (p < 0.01). These results were not influenced by parity or gestational age at delivery.
These data provide new information to help explain the biology of macrosomia and also highlight the need for stricter criteria for diagnosis and treatment of glucose intolerance.