Postnatal growth in children born small for gestational age with and without smoking mother

Background: Maternal smoking impairs fetal growth; however, if postnatal growth differs between children born small for gestational age (SGA) with smoking and non-smoking mother is unknown. Methods: Cohort-study of term born children born appropriate for gestational age with non-smoking mother (AGA-NS, n=30,561), SGA (birthweight <10th percentile) with smoking mother (SGA-S, n=171) or SGA with non-smoking mother (SGA-NS, n=1761). Means of height and weight measurements, collected at birth, 1.5, 3, 4 and 5 years, were compared using a generalized linear mixed effect model. Relative risks of short stature (<10th percentile) were expressed as adjusted risk ratios (aRR). Results: At birth, children born SGA-S were shorter than SGA-NS, but they did not differ in weight. At 1.5 years, SGA-S had reached the same height as SGA-NS. At 5 years, SGA-S were 1.1 cm taller and 1.2 kg heavier than SGA-NS. Compared with AGA-NS, SGA-S did not have increased risk of short stature at 1.5 or 5 years, while SGA-NS had increased risk of short stature at both ages; aRRs 3.0 (95% CI 2.6;3.4) and 2.3 (95% CI 2.0;2.7), respectively. Conclusions: Children born SGA-S have a more rapid catch-up growth than SGA-NS. This may have consequences for metabolic and cardiovascular health in children with smoking mothers.