Background and aims: Exposure to gestational diabetes mellitus (GDM) affects fetal growth, although this may vary between ethnic groups. There is limited knowledge about how GDM relates to postnatal growth. We aimed to investigate the association between GDM and body mass index (BMI) growth patterns from birth to 4-5 years of age in a multi-ethnic cohort in Norway, and the influence of ethnicity, mothers’ pre-pregnant BMI and gestational weight gain. 
Methods: Participants were children (ethnic European (n=346), South Asian (n=181), Middle East/North African (n=152)) drawn from the population-based STORK Groruddalen cohort of healthy women and offspring, followed from early pregnancy, all screened for GDM.  Using General linear models and Mixed models, we studied differences in BMI units and growth in BMI units per month (kg/m2). Growth intervals between 0-6 months and 6 months to 4-5 years of age were analyzed separately, and we adjusted for maternal age, parity, socioeconomic position, gestational age, and sex.
Results: Children exposed to GDM were not heavier at birth, but had a slower BMI growth (B=-0.120; 95%CI: -0.18- -0.04) during the first 6 months, compared to children not exposed to GDM. From 6 months to 4-5 years they had a faster BMI growth (B=0.009; 95%CI: 0.002-0.02), until their BMI at 4-5 years was similar to children not exposed to GDM. Maternal pre-pregnant obesity was associated with a higher BMI at birth, and a stable high BMI up to 4-5 years. Maternal pregnancy weight gain (highest tertile) was associated with higher BMI at birth and faster BMI growth from 6 months to 4-5 years (B=0.007; 95%CI: 0.0002-0.01). The relations between maternal GDM, pre-pregnant obesity, and gestational weight gain, and child BMI growth and were similar in all ethnic groups.
Conclusion: Children exposed to GDM were not heavier at birth, but had a slower body mass index (BMI) growth (catch-down growth) during the first 6 months.  Maternal pre-pregnant obesity was associated with a higher BMI at birth, and stable high BMI up to 4-5 years. Maternal pregnancy weight gain (highest tertile) was associated with higher BMI at birth, compared with the middle tertile, followed by faster BMI growth from 6 months to 4-5 years.

GROWTH PATTERNS IN A NORWEGIAN MULTI-ETHNIC COHORT OF PREESCHOOL CHILDREN; ASSOCIATIONS WITH IN UTERO EXPOSURE TO GESTATIONAL DIABETES MELLITUS