Risk factors for small for gestational age infants: a New Zealand study. New Zealand Cot Death Study Group.

AIM

The aim was to identify risk factors for small for gestational age infants.

METHOD

Case-control study. The study population was 1800 infants selected randomly from all babies born over a three year period over 78% of the country. Of these 1800 infants, 85 (4.8%) were classified as preterm (< 37 weeks completed gestation) and were excluded. 157 (8.9%) were classified as small for gestational age (cases) and 1519 (86.3%) were fullterm, nonsmall for gestational age infants (controls). Risk factors were investigated using data collected from obstetric records and parental interviews.

RESULTS

Risk factors associated with small for gestational age after controlling for potential confounders included maternal smoking during pregnancy (Odds ratio (OR) 2.61, 95% confidence interval (CI) 1.65, 4.15), primiparity (OR 2.96, 95% CI 1.59, 5.48), lack of antenatal care in the first trimester (OR 1.83, 95% CI 1.13, 2.98) and young age when mother left school (OR 1.56, 95% CI 1.01, 2.41). Use of marijuana in pregnancy significantly increased risk of small for gestational age at the 6% level (OR = 1.86, 95% CI 0.98, 3.52). The population attributable risk for maternal smoking was 31.1% (95% CI 18.2, 41.9).

CONCLUSION

Maternal smoking was the most important modifiable risk factor in this dataset for small for gestational age.