Risks of small-for-gestational-age births in immigrants: A nationwide epidemiological study in Sweden

Aim: To examine if there is an association between country of birth in parents and small-for-gestational-age (defined as a birthweight of more than two standard deviations (SDs) below the mean) in first singletons births. Methods: In this follow-up study, national population and healthcare registers were used to identify small-for-gestational-age births in all first singleton births in Sweden between 1 January 1982 and 31 December 2006. Odds ratios, standardised with regard to maternal age at birth, period of birth, marital status, family income, geographical region, employment, maternal height, and smoking history, were estimated by maternal and paternal country of birth. Singletons with both parents born in Sweden were used as reference group. Results: There were 1,060,467 records for first singletons births over the study period, of whom 3.5% were small-for-gestational-age. The rate was higher in newborns with non-Swedish born than in those with Swedish born mothers (4.1 and 3.3%, respectively). Immigrants from Southern European countries, Africa, and Asia had higher risks of small-for-gestational-age in than those in the reference group, and the risks were even higher in compatriot parents. Conclusions: Country of birth affected the risk of small-for-gestational-age. Maternity care should pay a special attention to pregnancies in certain population groups.