Low to Moderate Prenatal Alcohol Exposure and Neurodevelopmental Outcomes: A Narrative Review and Methodological Considerations

Prenatal exposure to alcohol and its impact on reward processing and substance use in adulthood

Heavy maternal alcohol drinking during pregnancy has been associated with altered neurodevelopment in the child but the effects of low-dose alcohol drinking are less clear and any potential safe level of alcohol use during pregnancy is not known. We evaluated the effects of prenatal alcohol on reward-related behavior and substance use in young adulthood and the potential sex differences therein. Participants were members of the European Longitudinal Study of Pregnancy and Childhood (ELSPAC) prenatal birth cohort who participated in its neuroimaging follow-up in young adulthood. A total of 191 participants (28-30 years; 51% men) had complete data on prenatal exposure to alcohol, current substance use, and fMRI data from young adulthood. Maternal alcohol drinking was assessed during mid-pregnancy and pre-conception. Brain response to reward anticipation and reward feedback was measured using the Monetary Incentive Delay task and substance use in young adulthood was assessed using a self-report questionnaire. We showed that even a moderate exposure to alcohol in mid-pregnancy but not pre-conception was associated with robust effects on brain response to reward feedback (six frontal, one parietal, one temporal, and one occipital cluster) and with greater cannabis use in both men and women 30 years later. Moreover, mid-pregnancy but not pre-conception exposure to alcohol was associated with greater cannabis use in young adulthood and these effects were independent of maternal education and maternal depression during pregnancy. Further, the extent of cannabis use in the late 20 s was predicted by the brain response to reward feedback in three out of the nine prenatal alcohol-related clusters and these effects were independent of current alcohol use. Sex differences in the brain response to reward outcome emerged only during the no loss vs. loss contrast. Young adult men exposed to alcohol prenatally had significantly larger brain response to no loss vs. loss in the putamen and occipital region than women exposed to prenatal alcohol. Therefore, we conclude that even moderate exposure to alcohol prenatally has long-lasting effects on brain function during reward processing and risk of cannabis use in young adulthood.

A dose-response analysis of the effects of prenatal alcohol exposure on cognitive development

BACKGROUND

Most studies of the effects of prenatal alcohol exposure (PAE) on cognitive function have assumed that the dose-response curve is linear. However, data from a few animal and human studies suggest that there may be an inflection point in the dose-response curve above which PAE effects are markedly stronger and that there may be differences associated with pattern of exposure, assessed in terms of alcohol dose per drinking occasion and drinking frequency.

METHODS

We performed second-order confirmatory factor analysis on data obtained at school age, adolescence, and early adulthood from 2227 participants in six US longitudinal cohorts to derive a composite measure of cognitive function. Regression models were constructed to examine effects of PAE on cognitive function, adjusted for propensity scores. Analyses based on a single predictor (absolute alcohol (AA)/day) were compared with analyses based on two predictors (dose/occasion and drinking frequency), using (1) linear models and (2) nonparametric general additive models (GAM) that allow for both linear and nonlinear effects.

RESULTS

The single-predictor GAM model showed virtually no nonlinearity in the effect of AA/day on cognitive function. However, the two-predictor GAM model revealed differential effects of maternal drinking pattern. Among offspring of infrequent drinkers, PAE effects on cognitive function were markedly stronger in those whose mothers drank more than ~3 drinks/occasion, and the effect of dose/occasion was strongest among the very frequent drinkers. Frequency of drinking did not appear to alter the PAE effect on cognitive function among participants born to mothers who limited their drinking to ~1 drink/occasion or less.

CONCLUSIONS

These findings suggest that linear models based on total AA/day are appropriate for assessing whether PAE affects a given cognitive outcome. However, examination of alcohol dose/occasion and drinking frequency is needed to fully characterize the impact of different levels of alcohol intake on cognitive impairment.

Dose-response effect of prenatal alcohol exposure on perinatal outcomes

BACKGROUND

A better understanding of the effects of lower levels of prenatal alcohol exposure (PAE), as a common exposure, is needed. The goal of this study was to examine the effects of mild-moderate PAE and episodic binge drinking on perinatal outcomes.

METHODS

The data were obtained from three prospective cohorts with a combined sample of 281 participants: 125 with PAE and 156 without PAE. Alcohol-related measures included the Alcohol Use Disorders Identification Test, timeline follow-back questionnaires (covering the periconceptional period, mid-gestation, and late gestation), and biomarkers. Absolute alcohol per day (AAD) and per drinking day (AADD), number of binge episodes, and maximum number of drinks in a 24-h period were estimated. Perinatal outcomes included gestational age and anthropometric measures. Data were analyzed using correlation and multivariable regression analysis.

RESULTS

Among women with PAE, average alcohol consumption across the periconceptional period and pregnancy was 0.37 oz ± 0.74 AA/day (~5 drinks/week). After adjusting for tobacco co-exposure and sociodemographic characteristics, significant associations between all alcohol measures and gestational age at delivery were observed, including cumulative measures of AAD (β = -0.58; 95% CI: -0.98; -0.17) and AADD (β = -0.58; 95% CI: -0.90; -0.26) during pregnancy and the periconceptional period. A significant association between the maximum number of drinks in a 24-h period and birth length percentile (β = -0.70; 95% CI: -1.36; -0.04) was observed in the final model. PAE was associated with lower birth weight percentile in univariate analyses only.

CONCLUSIONS

Results of this study demonstrate a negative association between mild-moderate PAE and episodic binge drinking with gestational age at delivery and birth length percentile after controlling for other factors. Robust negative effects of PAE, including in the periconceptional period before pregnancy recognition, on duration of gestation highlight the need for primary prevention efforts aimed at PAE in persons of reproductive age.

Predicting fetal alcohol spectrum disorders in preschool-aged children from early life factors

BACKGROUND

Early life factors, including parental sociodemographic characteristics, pregnancy exposures, and physical and neurodevelopmental features measured in infancy are associated with fetal alcohol spectrum disorders (FASD). The objective of this study was to evaluate the performance of a classifier model for diagnosing FASD in preschool-aged children from pregnancy and infancy-related characteristics.

METHODS

We analyzed a prospective pregnancy cohort in Western Ukraine enrolled between 2008 and 2014. Maternal and paternal sociodemographic factors, maternal prenatal alcohol use and smoking behaviors, reproductive characteristics, birth outcomes, infant alcohol-related dysmorphic and physical features, and infant neurodevelopmental outcomes were used to predict FASD. Data were split into separate training (80%: n = 245) and test (20%: n = 58; 11 FASD, 47 no FASD) datasets. Training data were balanced using data augmentation through a synthetic minority oversampling technique. Four classifier models (random forest, extreme gradient boosting [XGBoost], logistic regression [full model] and backward stepwise logistic regression) were evaluated for accuracy, sensitivity, and specificity in the hold-out sample.

RESULTS

Of 306 children evaluated for FASD, 61 had a diagnosis. Random forest models had the highest sensitivity (0.54), with accuracy of 0.86 (95% CI: 0.74, 0.94) in hold-out data. Boosted gradient models performed similarly, however, sensitivity was less than 50%. The full logistic regression model performed poorly (sensitivity = 0.18 and accuracy = 0.65), while stepwise logistic regression performed similarly to the boosted gradient model but with lower specificity. In a hold-out sample, the best performing algorithm correctly classified six of 11 children with FASD, and 44 of 47 children without FASD.

CONCLUSIONS

As early identification and treatment optimize outcomes of children with FASD, classifier models from early life characteristics show promise in predicting FASD. Models may be improved through the inclusion of physiologic markers of prenatal alcohol exposure and should be tested in different samples.