Thymic size correlates with cord blood zinc levels in low-birth-weight newborns

Thymus is essential for immunity as it provides environment for T cell differentiation and maturation. There is limited information on various factors which determine thymic size at birth. We studied the influence of cord blood zinc and copper levels and maternal and neonatal nutritional status on thymic size in term low-birth-weight (LBW) newborns. A prospective observational study on 44 term LBW (< 2,500 g) newborns (cases) and 71 gestational age-matched newborns weighing a parts per thousand yen2,500 g (controls). Sonographically determined thymic index was correlated to cord blood zinc and copper levels and maternal and neonatal nutritional status. Thymic index measured 3.74 +/- 1.57 cm(3) in LBW newborns compared to 4.90 +/- 2.33 cm(3) in normal-birth-weight newborns. Thymic index was significantly correlated to cord blood zinc levels but not to cord blood copper levels and had linear relationship to the maternal body mass index and midarm circumference and neonatal anthropometric parameters. Conclusion: Thymic index is linearly related to cord blood zinc levels and maternal and neonatal nutritional status. Compared to thymic size in the Western newborns, the thymus is less than half in size in Indian newborns of normal birth weight. Reduced thymic size in Indian newborns in general and LBW infants in particular may have consequences for their immune competence and the risk of infections. Improving nutrition of pregnant women, particularly zinc nutriture might favorably influence thymic size in their offspring.