Modelling foetal growth in a bi-ethnic sample: results from the Born in Bradford (BiB) birth cohort

Background: Attempts to explain the increased risk for metabolic disorders observed in South Asians have focused on the "South Asian'' phenotype at birth and subsequent post-natal growth, with little research on pre-natal growth. Aim: To identify whether divergent growth patterns exist for foetal weight, head (HC) and abdominal circumferences (AC) in a sample of Pakistani and White British foetuses. Subjects and methods: Models were based on 5553 (weight), 5154 (HC) and 5099 (AC) foetuses from the Born in Bradford birth cohort. Fractional polynomials and mixed effects models were employed to determine growth patterns from similar to 15 weeks of gestation-birth. Results: Pakistani foetuses were significantly smaller and lighter as early as 20 weeks. However, there was no ethnic difference in the growth patterns of weight and HC. For AC, Pakistani foetuses displayed a trend for reduced growth in the final trimester. Conclusion: As the pattern of weight and HC growth was not significantly different during the period under investigation, the mechanism culminating in the reduced Pakistani size at birth may act earlier in gestation. Reduced AC growth in Pakistanis may represent reduced growth of the visceral organs, with consequences for post-natal liver metabolism and renal function.