Association of light-to-moderate alcohol drinking in pregnancy with preterm birth and birth weight: elucidating bias by pooling data from nine European cohorts

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Katrine Strandberg-Larsen, Gry Poulsen, Bodil Hammer Bech, Leda Chatzi, Sylvaine Cordier, Maria Teresa Grønning Dale, Marieta Fernandez, Tine Brink Henriksen, Vincent W. V. Jaddoe, Manolis Kogevinas, Claudia J. Kruithof, Morten Søndergaard Lindhard, Per Magnus, Ellen Aagaard Nohr, Lorenzo Richiardi, Clara L. Rodriguez-Bernal, Florence Rouget, Franca Rusconi, Martine Vrijheid, Anne-Marie Nybo Andersen

Women who drink light-to-moderately during pregnancy have been observed to have lower risk of unfavourable pregnancy outcomes than abstainers. This has been suggested to be a result of bias. In a pooled sample, including 193 747 live-born singletons from nine European cohorts, we examined the associations between light-to-moderate drinking and preterm birth, birth weight, and small-for-gestational age in term born children (term SGA). To address potential sources of bias, we compared the associations from the total sample with a sub-sample restricted to first-time pregnant women who conceived within six months of trying, and examined whether the associations varied across calendar time. In the total sample, drinking up to around six drinks per week as compared to abstaining was associated with lower risk of preterm birth, whereas no significant associations were found for birth weight or term SGA. Drinking six or more drinks per week was associated with lower birth weight and higher risk of term SGA, but no increased risk of preterm birth. The analyses restricted to women without reproductive experience revealed similar results. Before 2000 approximately half of pregnant women drank alcohol. This decreased to 39% in 2000–2004, and 14% in 2005–2011. Before 2000, every additional drink was associated with reduced mean birth weight, whereas in 2005–2011, the mean birth weight increased with increasing intake. The period-specific associations between low-to-moderate drinking and birth weight, which also were observed for term SGA, are indicative of bias. It is impossible to distinguish if the bias is attributable to unmeasured confounding, which change over time or cohort heterogeneity.
Original languageEnglish
JournalEuropean Journal of Epidemiology
Volume32
Issue number9
Pages (from-to)751-764
Number of pages14
ISSN0393-2990
DOIs
Publication statusPublished - Sep 2017

    Research areas

  • Alcohol, Birth weight, Cohort study, Confounding, Preterm birth, Small for gestational age

ID: 188196961