The impact of maternal smoking on fetal and infant growth.
BACKGROUND
Low birth weight is associated with accelerated postnatal growth and adverse adult health outcomes. Maternal smoking is a major risk factor for low birth weight. This study aims to assess: Pre- and postnatal growth associated with maternal smoking compared to other risk factors for low birth weight. The effect of reduction of maternal smoking on growth.


METHODS
A cohort (n=269) followed with ultrasound measurements in the third trimester and postnatal anthropometric measurements until 6 months of age. Mothers were interviewed about their smoking habits at 18 and 28 weeks of pregnancy.


RESULTS
Maternal smoking was associated with a greater reduction in birth length SDS than other causes of equally reduced birth weight (mean difference: -0.25 SDS, P=0.013). The adjustment of gestational age, based on bi-parietal diameter at an early dating scan, indicated that mothers who reduced smoking carried smaller fetuses than mothers who continued to smoke heavily (mean difference=2.6 days, P=0.012). Birth weights in these two groups were similar (P=0.87). However at 3 months of age, reduced smoking was associated with lower weight (mean difference=-0.38 SDS, P=0.045).


CONCLUSIONS
Maternal smoking was associated with a reduction of linear growth, which was more marked than that of other risk factors, and which seemed to occur before the 3rd trimester. The results indicated a beneficial effect of reduction of smoking upon third trimester growth, and that the decision to reduce smoking in mid-pregnancy may be influenced by early fetal size.
Vielwerth
S E
SE
University Department of Neonatology, Rigshospitalet, Section 5023, Blegdamsvej 9, DK-2100 Copenhagen, Denmark. signe.vielwerth@rh.hosp.dk
Jensen
R B
RB
Larsen
T
T
Greisen
G
G
D005260:Female; D047109:Fetal Development / Q000187:drug effects*; D006801:Humans; D007223:Infant; D007230:Infant, Low Birth Weight / Q000254:growth & development*; D007231:Infant, Newborn; D011247:Pregnancy; D011297:Prenatal Exposure Delayed Effects; D012907:Smoking / Q000009:adverse effects*