A Commentary on the
Book: “Expecting Better: Why the Conventional Pregnancy Wisdom is Wrong and
What You Really Need to Know” by Emily Oster, Ph.D. Associate Professor of Economics, University
of Chicago.
Multiple
health authorities, including The United States Surgeon General, the American
College of Obstetricians and Gynecologists, the Canadian Society of
Obstetricians and Gynecologists, and the Public Health Agency of Canada, all
advise that pregnant women and women who may become pregnant should abstain
from alcohol consumption. In her recent
book, Dr. Oster challenges these health authorities and this recommendation, arguing
that moderate drinking during pregnancy is safe (for example, a glass of wine
per day). Although the definition of
moderate drinking varies by country, consumption of 1 standard drink/day (containing
approximately 0.5 fl oz of pure ethanol in the U.S.) is generally considered
moderate drinking for non-pregnant women (Dufour,
1999).
Dr. Oster’s book suggests that the available scientific evidence does
not support the recommendation to abstain from alcohol use during pregnancy. This is not the case, as the current
scientific evidence strongly indicates that even light drinking during
pregnancy can have long-lasting negative impact on brain function in children
that persists into adulthood. Below is a
summary of key scientific studies that have demonstrated significant adverse
effects of alcohol at levels that can be achieved during light drinking. We will begin with a review of studies that
have been conducted with humans.
1.
In a population
cohort with low socio-economic status and mixed ethnicity (46% Caucasian and
54% African-American) moderate alcohol exposure during the first trimester of
pregnancy was associated with significant deficits in verbal learning during
adolescence (Willford
et al., 2004).
2.
Other studies with different human populations have
demonstrated a link between light drinking and behavioral and cognitive
problems during childhood and/or adolescence, including alterations in working
memory, attention and social interactions (Burden
et al., 2005, Coles et al., 1991, O'Leary
et al., 2010, Sayal et al., 2007, Sood
et al., 2001).
3.
A recent study demonstrated that five variants of genes
involved in alcohol metabolism in children and their mothers were associated
with cognitive ability at 8 years of age in children born to mothers that reported
drinking alcohol in moderation (1-6 drinks/week) during pregnancy. This finding
indicates that certain pregnant women may be more susceptible to the effects of
light drinking and that this may be related to genetic factors that regulate
their ability to metabolize alcohol (Lewis
et al., 2012).
4.
In a landmark longitudinal cohort study, Day and
collaborators (Day
et al., 2013) demonstrated that low-moderate prenatal alcohol causes
significant behavioral problems (for example, attention deficits) that persist
into adulthood (22 years of age).
5.
A recent brain imaging study demonstrated that
low-moderate ethanol exposure during fetal development was associated with
reductions in gray matter volume in several brain regions at approximately 20
years of age (Eckstrand
et al., 2012).
6.
A recent analysis of several separate studies (i.e., a meta-analysis)
found a significant detrimental effect of light-moderate prenatal alcohol
exposure on child behavior (Flak
et al., 2013). The problem
behaviors identified in exposed children include increased need for attention,
deficient interactive play skills, and behavioral modulation alterations.
7.
A study with humans found that newborns of mothers that
consumed light amounts of alcohol during pregnancy had a higher frequency of
facial malformations and alterations in umbilical cord artery contractility (Iveli
et al., 2007).
Studies with laboratory
animals support the findings of these human studies, demonstrating persistent
effects of light-moderate alcohol exposure on the brain (Valenzuela
et al., 2012). The importance
of animal studies is that other risk factors (for example, nutrition, genetics,
environmental influences) are controlled for and, therefore, the effects of
alcohol exposure can be quantified.
1.
Adult offspring of pregnant rats who consumed low levels
of alcohol displayed deficits in behavioral tests of learning and memory (Savage
et al., 2002, Savage et al., 2010). Alterations in
the strength of transmission of information between neurons were identified as
a potential factor responsible for these deficits in learning and memory (Varaschin
et al., 2010).
2.
In addition, it was discovered that moderate alcohol
exposure affects the generation of new neurons in brain regions important for
learning and memory, and this could also contribute to the deficits observed in
the exposed offspring (Choi
et al., 2005, Uban et al., 2010, Akers
et al., 2011, Roitbak et al., 2011).
3.
Exposure of pregnant macaque monkeys to moderate alcohol
levels has also been shown to impair motor coordination and delayed response
speed in infant offspring (reviewed in (Schneider
et al., 2011)).
4.
Long-lasting alterations in social behavior were recently
demonstrated in adult offspring of rats exposed to moderate alcohol levels
during pregnancy (Hamilton
et al., 2010).
5.
Moderate alcohol
exposure increased preference and consumption of alcohol-containing solutions
in adult offspring; adult rats from the ethanol group also exhibited increased
cocaine and amphetamine consumption after cocaine exposure (Barbier
et al., 2009, Barbier et al., 2008). This moderate
prenatal alcohol exposure may increase the risk of developing alcoholism and
other addiction-related disorders.
6.
A study with primates showed a reduction in aversive
responses to repetitive tactile stimulation in young adult monkeys exposed to low
levels of alcohol throughout gestation that could result in impaired control of
sensory input (Schneider
et al., 2008, Schneider et al., 2011).
In
conclusion, the collective evidence from human and animal studies strongly suggests
that even light drinking during pregnancy can produce significant long-lasting alterations
in the brain, adversely affecting behavior, cognition, and social skills. Given
the current state of the scientific evidence, the safest course of action is to
advise pregnant women and women who may become pregnant to avoid drinking
alcohol, even at low levels, during any stage of pregnancy.
James
Reynolds, Ph.D. President
C. Fernando
Valenzuela, M.D., Ph.D., Vice-president
Alexandre
Medina, Ph.D., Treasurer
Jeffrey
Wozniak, Ph.D. Secretary
Fetal Alcohol Spectrum Disorder Study
Group-Research Society on Alcoholism
References
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