IGF1 and obesity due to melanocortin 4 receptor deficiency: Infants with higher IGF-I levels were comparable to those with lower levels with respect to maternal age (P = 0.65), race (P = 0.83), maternal education (P = 0.38), maternal smoking (P = 0.63), obesity (P = 0.28), and gestational age (P = 0.91) (Table 2), although they may differ by delivery route (P = 0.14).