Effect of smoking among Indigenous and non-Indigenous mothers on preterm birth and full-term low birthweight

Objective: To estimate the percentage of preterm (< 37 weeks) and full-term low-birthweight (37-41 weeks, < 2500 g) babies born to mothers who smoke, stratified by Indigenous status and statistically adjusted for the potential confounding effects of social and demographic factors, medical conditions and pregnancy complications. Design, setting and participants: Population-based study of singleton babies born to mothers resident in Queensland who gave birth in Queensland from 1 July 2005 to 31 December 2006. Main outcome measures: Adjusted percentages of preterm birth and full-term low birthweight for babies born to Indigenous and non-Indigenous mothers. Results: Of the 79803 babies studied, 4228 (5.3%) were born to Indigenous mothers and 16395 (20.5%) were born to mothers who smoked during pregnancy. The percentage of Indigenous mothers who smoked (54%) was almost triple that for non-Indigenous mothers (risk ratio, 2.90; 95% Cl, 2.81-2.99). The adjusted outcomes for babies born to Indigenous non-smokers were similar to those for non-Indigenous non-smokers (preterm, 7.1% v 6.1%; full-term low birthweight, 1.6% v 1.1%). The adjusted percentages for smokers were high regardless of Indigenous status (preterm, Indigenous v non-Indigenous, 8.3% v 7.8%; full-term low birthweight, Indigenous v non-Indigenous, 5.3% v 3.7%). Conclusions: Antenatal smoking remains an important cause of poor health among both Indigenous and non-Indigenous newborn babies. Most pregnant smokers receive their antenatal care in the public sector. State and federal governments, who directly fund this sector, have a particular responsibility to ensure that interventions are offered to all pregnant smokers to help them quit smoking.