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Eur J Epidemiol. 2017 Sep;32(9):751-764. doi: 10.1007/s10654-017-0323-2. Epub 2017 Oct 12.

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

Author information

1
Section for Social Medicine, Department of Public Health, University of Copenhagen, Øster Farimagsgade 5, Postbox 2099, 1014, Copenhagen K, Denmark. ksla@sund.ku.dk.
2
Section for Social Medicine, Department of Public Health, University of Copenhagen, Øster Farimagsgade 5, Postbox 2099, 1014, Copenhagen K, Denmark.
3
Department of Public Health, Section for Epidemiology, Aarhus University, Aarhus, Denmark.
4
Department of Social Medicine, Faculty of Medicine, University of Crete, Rethimno, Greece.
5
National Institute of Health and Medical Research (INSERM), U1085-IRSET, University of Rennes, Rennes, France.
6
Norwegian Institute of Public Health, Oslo, Norway.
7
Department of Psychology, University of Oslo, Oslo, Norway.
8
University of Granada, Granada, Spain.
9
Department of Pediatrics, Perinatal Epidemiology Research Unit, Aarhus University Hospital, Aarhus, Denmark.
10
The Generation R Study Group, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands.
11
Department of Epidemiology, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands.
12
Department of Pediatrics, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands.
13
ISGlobal Centre for Research in Environmental Epidemiology (CREAL), Barcelona, Spain.
14
Research Unit for Gynaecology and Obstetrics, Institute of Clinical Research, University of Southern Denmark, Odense M, Denmark.
15
Cancer Epidemiology Unit, Department of Medical Sciences, University of Turin and CPO-Piemonte, Turin, Italy.
16
FISABIO-Universitat Jaume I-Universitat de València Joint Research Unit of Epidemiology and Environmental Health, València, Spain.
17
Health Services Research Area, FISABIO Salud Pública.Valencia, Valencia, Spain.
18
Red de Investigación en Servicios de Salud en Enfermedades Crónicas (REDISSEC), Tenerife, Spain.
19
Unit of Epidemiology, Meyer Children's University Hospital, Florence, Italy.
20
University Pompeu Fabra, Barcelona, Spain.
21
CIBER Epidemiología y Salud Pública (CIBERESP), Madrid, Spain.

Abstract

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.

KEYWORDS:

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

PMID:
29027084
DOI:
10.1007/s10654-017-0323-2
[Indexed for MEDLINE]
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