The effect of smoking tobacco on neonatal body composition

OBJECTIVE: Our purpose was to examine the differences in body composition in infants of women who smoke compared with those of nonsmokers, STUDY DESIGN: Within 24 hours of birth anthropometric measurements and total body electrical conductivity estimates of body composition were obtained on 129 term infants (30 born to women who smoked tobacco during pregnancy and 99 born to women who did not smoke). Anthropometric measurements included weight, skinfolds, circumferences, and crown-heel and extremity lengths. RESULTS: There was a significant decrease in weight in the infants of smokers (3145 +/- 414 gm vs 3354 +/- 525 gm, p = 0.05). There was a decrease in crown-heel length (49.2 +/- 2.0 cm vs 50.1 +/- 2.2 cm, p = 0.03); the length of the lower leg (7.9 +/- 0.6 cm vs 8.4 +/- 0.6 cm, p = 0.0001), upper leg (9.1 +/- 0.7 cm vs 9.9 +/- 0.8 cm, p = 0.0001), and the lower arm (7.2 +/- 0.5 cm vs 7.5 +/- 0.4 cm, p = 0.0001). There were no significant differences in the skinfold and limb circumference measurements. infants of smokers had significantly decreased fat-free mass as estimated by total body electrical conductivity (2799 +/- 292 gm vs 2965 +/- 359 gm, p = 0.02) but no significant difference in fat mass (343 +/- 164 gm vs 387 +/- 216 gm, p = 0.32). CONCLUSIONS: The decrease in birth weight in infants of women who smoked is primarily due to a decrease in fat-free mass.