Colin MacKenzie M.D.
December 23, 2020

Is even light alcohol use during pregnancy potentially harmful to the unborn child?


Alcohol is a well known fetal teratogen (agent that causes malformations) in utero. It has been shown to influence the development of fetal brain regions by causing hypoxia, cell death, and abnormalities in neural proliferation and migration. The teratogenic outcomes are variable across brain regions and correspond to differences in frequency, dose, and timing of alcohol exposure in the womb. 

The prevalence of alcohol consumption during pregnancy is approximately 10%. The exposure of alcohol during pregnancy is associated with illness in children postnatally including poor behavioral and cognitive effects. 

There are numerous studies regarding the unfavorable consequences linked with heavy alcohol exposure in pregnancy.  However, there is far less research dealing with the effects of lighter alcohol exposure during pregnancy, which is defined as 7 drinks per week.  


The study by Briana and Colleagues published in the American journal of psychiatry tries to address these effects. A total of 9,719 children (aged 9 -10 years) were included in the study of which 2,518 (25.9%) had been exposed to some degree of alcohol in utero. Various sources of data were used including child and parental self-reports, clinical interviews, cognitive tasks, and structural and resting-state functional MRI findings. 


The study found that children exposed prenatally to even light alcohol use had higher rates of psychological and behavioral problems.  Problems identified at a higher frequency included various phobias, separation anxiety disorder, oppositional defiant disorder, and attention deficit hyperactivity disorder [ADHD]. 

Some of the negative outcomes displayed a dose-dependent response.  Offspring of heavier drinkers displayed more depression, rule breaking, aggressive behaviors, and attention deficits in comparison to children of light drinkers. 

Prenatal alcohol exposure was also associated with anatomical alterations in the temporal, occipital, and parietal lobes. These anatomical differences were also linearly associated with the number of drinks consumed. Some of the behavioral and psychological outcomes at baseline and at the one-year follow-up could be explained by variations in brain structure in the exposed children. However, there was no change in resting-state functional connectivity in youth with in-utero alcohol exposure. 


Light exposure to alcohol is linked with psychological and behavioral issues inclusive of attention deficits, greater impulsivity, as well as mood and anxiety disorders. Exposure to alcohol during pregnancy has subtle, but important, psychological and behavioral effects in youth. Therefore, it is always advisable for females to refrain from alcohol intake throughout the pregnancy period.

Lees B, Mewton L, Jacobus J, Valadez EA, Stapinski LA, Teesson M, Tapert SF, Squeglia LM. Association of Prenatal Alcohol Exposure with Psychological, Behavioral, and Neurodevelopmental Outcomes in Children from the Adolescent Brain Cognitive Development Study. Am J Psychiatry. 2020 Nov 1;177(11):1060-1072. doi: 10.1176/appi.ajp.2020.20010086. Epub 2020 Sep 25. PMID: 32972200.