Objective To examine the individual association between advancing maternal age, body mass index (BMI) and racial origin with the development of gestational diabetes mellitus (GDM) and the interaction between these factors. Design Retrospective study. Setting Fifteen maternity units in northwest London between 1988 and 2000. Population The study included 1688 women who developed GDM and 172 632 who did not. All women were nulliparous. BMI was calculated at first antenatal visit and maternal age and racial origin (White European, Black African, Black Caribbean or South Asian) were self-reported. Methods Binary logistic regression analysis. Main outcome measures Development of GDM within each racial group. Results There was a strong positive association between advancing maternal age and increasing BMI, individually, and the development of GDM (P < 0.01 for both). Compared with White Europeans aged 20-24 years, the odds ratios for GDM development were significantly higher in women older than 30 years if they were White Europeans (P < 0.001), older than 25 years if they were Black Africans (P < 0.001) and older than 20 years if they were South Asians (P < 0.001). The odds ratios for GDM development were significantly higher in Black Africans and South Asians (P < 0.001 for both) irrespective of BMI, compared with White Europeans with normal BMI. Conclusion Maternal age and BMI interact with racial group in relation to the prevalence of GDM. Both factors are important in the development of GDM, particularly so in Black African and South Asian women.
