What accounts for ethnic differences in newborn skinfold thickness comparing South Asians and White Caucasians? Findings from the START and FAMILY Birth Cohorts

Abstract

Objective: South Asians are a high-risk group for type 2 diabetes and coronary heart disease. We sought to determine ethnic differences in newborn adiposity comparing South Asians (SA) to White Caucasians (Whites).

Methods: Seven hundred ninety pregnant women (401 SA, 389 Whites) and their full-term offspring from two birth cohorts in Canada were analyzed. Pregnant women completed a health assessment including a 75-g oral glucose tolerance test to assess for dysglycemia. Birthweight, length, waist and hip circumference, and triceps and subscapular skinfold thickness (a surrogate measure of body adiposity) were measured in all newborns. Multivariate regression was used to identify maternal factors associated with newborn skinfold measurements.

Results: South Asian women were younger (30.1 vs 31.8 years, P<0.001), their prepregnancy body mass index was lower (23.7 vs 26.2, P<0.0001) and gestational diabetes was substantially higher (21% vs 13%, P=0.005) compared with Whites. Among full-term newborns, South Asians had lower birthweight (3283 vs 3517 g, P=0.0001), had greater skinfold thickness (11.7 vs 10.6 mm; P=0.0001) and higher waist circumference (31.1 vs 29.9 cm, P=0.0001) compared with Whites. Risk factors for newborn skinfold thickness included South Asian ethnicity (standardized estimate (s.e.): 0.24; P<0.0001), maternal glucose (s.e.: 0.079; P=0.04) and maternal body fat (s.e.: 0.14; P=0.0002).

Conclusions: South Asian newborns are lower birthweight and have greater skinfold thickness, compared with White newborns, and this is influenced by maternal body fat and glucose. Interventions aimed at reducing body fat prior to pregnancy and gestational diabetes during pregnancy in South Asians may favorably alter newborn body composition and require evaluation.

Figure 1

Mean skinfold thickness by birthweight quartiles comparing South Asian and White newborns adjusting for newborn age, sex and age at birth visit. Using continuous birthweight, South Asian newborns have higher skinfolds over all birthweights (P<0.0001); the increasing trend in both ethnic groups is significant (P<0.0001). Note that adjustment for GDM makes no appreciable difference in the results.

Figure 2

Newborn skinfold thickness by ponderal index (kg m⁻³). White newborns have a higher ponderal index over all skinfolds (P<0.0001); the increasing trend in both ethnic groups is significant (P<0.0001). There is no significant interaction (P=0.19).

Figure 3

Newborn body composition by maternal AUC glucose tertiles (women receiving insulin during pregnancy excluded), adjusting for newborn sex and gestational age. Ethnic differences are significant for each newborn parameter (P<0.0001 for each). Birthweight, skinfold thickness, and ponderal index increase with increasing AUC glucose (continuous measure) adjusting for newborn sex and gestational age (P<0.0001, P=0.0006, P<0.0001 respectively); while there is no trend found with birthlength (P=0.57).