Prenatal alcohol exposure and child sleep problems: A family-based quasi-experimental study.

Background: We examine whether associations between prenatal exposure to hazardous maternal alcohol consumption during the first trimester of pregnancy and sleep problems in young children represent a causal association.

Methods: The population-based sample consists of 15,911 mothers with 30,395 offspring from the Norwegian Mother, Father, and Child Cohort Study (MoBa) and the Medical Birth Registry of Norway (MBRN). Women self-reported pre-pregnancy alcohol consumption and consumption during the first trimester of pregnancy twice: at gestational weeks 17 and 30. Mothers reported their children's sleep problems, when they were 1.5 and 3 years (mean = 50; SD = 10). We tested models adjusting for (1) measured confounders, (2) unmeasured familial risk factors by sibling design, and (3) maternal hazardous drinking in the 3 months prior to pregnancy as an instrumental variable within the sibling design.

Results: Children of mothers with hazardous drinking during the first trimester were at increased risk of sleep problems at 1.5 ( = 1.14, 95%CI 0.04-2.25) and 3 ( = 2.86, 95%CI 1.85-3.87) years of age. These associations were reduced to close to zero and non-significant at 1.5 ( = -0.32, 95%CI -1.91-1.26) and 3 ( = 0.06, 95%CI -1.56-1.64) years when controlling for both familial and measured environmental risk factors.

Conclusions: There is a moderate association between maternal hazardous drinking during pregnancy and offspring sleep problems up to age three. This association is explained by risk factors differing between families and does not reflect a cause-effect relationship.