Large birth size programs an elevated risk of type 2 diabetes in adulthood, but data are absent concerning glucose metabolic health impact in infancy. We sought to determine whether the large birth size is associated with insulin resistance and β-cell function in infancy and evaluate the determinants.
Design and participants
In the Canadian 3D birth cohort, we conducted a nested matched (1:2) study of 70 large-for-gestational-age (LGA, birth weight >90th percentile) and 140 optimal-for-gestational-age (OGA, 25th–75th percentiles) control infants. The primary outcomes were homeostasis model assessment of insulin resistance (HOMA-IR) and beta-cell function (HOMA-β) at age 2-years.
HOMA-IR and HOMA-β were similar in LGA and OGA infants. Adjusting for maternal and infant characteristics, decelerated growth in length during early infancy (0–3 months) was associated with a 25.8% decrease (95% confidence intervals 6.7–41.0%) in HOMA-β. During mid-infancy (3–12 months), accelerated growth in weight was associated with a 25.5% (0.35–56.9%) increase in HOMA-IR, in length with a 69.3% increase (31.4–118.0%) in HOMA-IR and a 24.5% (0.52–54.3%) increase in HOMA-β. Decelerated growth in length during late infancy (1–2 years) was associated with a 28.4% (9.5–43.4%) decrease in HOMA-IR and a 21.2% (3.9–35.4%) decrease in HOMA-β. Female sex was associated with higher HOMA-β, Caucasian ethnicity with lower HOMA-IR, and maternal smoking with lower HOMA-β.
This study is the first to demonstrate that large birth size is not associated with insulin resistance and β-cell function in infancy but infancy growth pattern matters. Decelerated infancy growth may be detrimental to beta-cell function.