Differences in BMI z-scores between offspring of smoking and nonsmoking mothers: a longitudinal study of German children from birth through 14 years of age.
BACKGROUND
Children of mothers who smoked during pregnancy have a lower birth weight but have a higher chance to become overweight during childhood.


OBJECTIVE
We followed children longitudinally to assess the age when higher body mass index (BMI) z-scores became evident in the children of mothers who smoked during pregnancy, and to evaluate the trajectory of changes until adolescence.


METHODS
We pooled data from two German cohort studies that included repeated anthropometric measurements until 14 years of age and information on smoking during pregnancy and other risk factors for overweight. We used longitudinal quantile regression to estimate age- and sex-specific associations between maternal smoking and the 10th, 25th, 50th, 75th, and 90th quantiles of the BMI z-score distribution in study participants from birth through 14 years of age, adjusted for potential confounders. We used additive mixed models to estimate associations with mean BMI z-scores.


RESULTS
Mean and median (50th quantile) BMI z-scores at birth were smaller in the children of mothers who smoked during pregnancy compared with children of nonsmoking mothers, but BMI z-scores were significantly associated with maternal smoking beginning at the age of 4-5 years, and differences increased over time. For example, the difference in the median BMI z-score between the daughters of smokers versus nonsmokers was 0.12 (95% CI: 0.01, 0.21) at 5 years, and 0.30 (95% CI: 0.08, 0.39) at 14 years of age. For lower BMI z-score quantiles, the association with smoking was more pronounced in girls, whereas in boys the association was more pronounced for higher BMI z-score quantiles.


CONCLUSIONS
A clear difference in BMI z-score (mean and median) between children of smoking and nonsmoking mothers emerged at 4-5 years of age. The shape and size of age-specific effect estimates for maternal smoking during pregnancy varied by age and sex across the BMI z-score distribution.
Institute of Social Paediatrics and Adolescent Medicine, and.
Christina
C
Riedel
Nora
N
Fenske
Manfred J
MJ
Müller
Sandra
S
Plachta-Danielzik
Thomas
T
Keil
Linus
L
Grabenhenrich
Rüdiger
R
von Kries
D000293:Adolescent; D000367:Age Factors; D015992:Body Mass Index; D002648:Child; D002675:Child, Preschool; D005260:Female; D005858:Germany; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008137:Longitudinal Studies; D008297:Male; D009035:Mothers; D050177:Overweight / Q000139:chemically induced / Q000453:epidemiology*; D011247:Pregnancy; D011297:Prenatal Exposure Delayed Effects / Q000139:chemically induced / Q000453:epidemiology*; D012044:Regression Analysis; D012307:Risk Factors; D012907:Smoking / Q000009:adverse effects*