Benchmark dose profiles for bivariate exposures.

While benchmark dose (BMD) methodology is well-established for settings with a single exposure, these methods cannot easily handle multidimensional exposures with nonlinear effects. We propose a framework for BMD analysis to characterize the joint effect of a two-dimensional exposure on a continuous outcome using a generalized additive model while adjusting for potential confounders via propensity scores. This leads to a dose-response surface which can be summarized in two dimensions by a contour plot in which combinations of exposures leading to the same expected effect are identified. In our motivating study of prenatal alcohol exposure, cognitive deficits in children are found to be associated with both the frequency of drinking as well as the amount of alcohol consumed on each drinking day during pregnancy. The general methodological framework is useful for a broad range of settings, including combinations of environmental stressors, such as chemical mixtures, and in explorations of the impact of dose rate rather than simply cumulative exposure on adverse outcomes.

Evolution of the Physical Phenotype of Fetal Alcohol Spectrum Disorders from Childhood through Adolescence.

BACKGROUND: This paper reports findings from the first longitudinal study on the evolution of the physical phenotypes of fetal alcohol syndrome (FAS) and partial FAS (PFAS) from early childhood through adolescence. METHODS: The sample consisted of 155 children (78 males and 77 females) born to women recruited at an antenatal clinic serving a Cape Coloured (mixed ancestry) population in Cape Town, South Africa. Two expert FASD dysmorphologists, blind regarding prenatal alcohol exposure, independently evaluated each child's growth and dysmorphology at 4 clinics conducted over an 11-year period. Case conferences were held to reach consensus regarding which children had FAS or PFAS growth and physical features using the Revised Institute of Medicine (2005) guidelines. RESULTS: The prevalence of the physical phenotype was stable across the 4 ages for about half of the children with FAS and about one-third of those with PFAS but more variable for the others. Test-retest reliability was substantial for the FAS phenotype, but poorer for PFAS. Two distinct patterns were seen: a "strong phenotype" that was consistently identified and a less consistent one in which dysmorphic features and/or anthropometric deficits fluctuated or diminished with age. The physical phenotype was most apparent during early childhood and least apparent during puberty, due to differences in timing of the growth spurt and the evolving adult face. Short palpebral features and small head circumference diminished with age, flat philtrum fluctuated, while thin vermilion and weight and height restriction were stable. CONCLUSIONS: Key facial features that characterize FASD in early childhood diminish or evolve in some individuals, making diagnostic examinations that rely on these characteristics most sensitive during early childhood and school age. Moreover, puberty poses classification problems due to variability in timing of the growth spurt. Given that several features and small head circumference diminished with age, many individuals would be misdiagnosed if only examined at a later age.

Maternal choline supplementation mitigates alcohol exposure effects on neonatal brain volumes.

BACKGROUND: Prenatal alcohol exposure (PAE) is associated with smaller regional and global brain volumes. In rats, gestational choline supplementation mitigates adverse developmental effects of ethanol exposure. Our recent randomized, double-blind, placebo-controlled maternal choline supplementation trial showed improved somatic and functional outcomes in infants at 6.5 and 12 months postpartum. Here, we examined whether maternal choline supplementation protected the newborn brain from PAE-related volume reductions and, if so, whether these volume changes were associated with improved infant recognition memory. METHODS: Fifty-two infants born to heavy-drinking women who had participated in a choline supplementation trial during pregnancy underwent structural magnetic resonance imaging with a multi-echo FLASH protocol on a 3T Siemens Allegra MRI (median age = 2.8 weeks postpartum). Subcortical regions were manually segmented. Recognition memory was assessed at 12 months on the Fagan Test of Infant Intelligence (FTII). We examined the effects of choline on regional brain volumes, whether choline-related volume increases were associated with higher FTII scores, and the degree to which the regional volume increases mediated the effects of choline on the FTII. RESULTS: Usable MRI data were acquired in 50 infants (choline: n = 27; placebo: n = 23). Normalized volumes were larger in six of 12 regions in the choline than placebo arm (t ≥ 2.05, p ≤ 0.05) and were correlated with the degree of maternal choline adherence (ß ≥ 0.28, p ≤ 0.04). Larger right putamen and corpus callosum were related to higher FTII scores (r = 0.36, p = 0.02) with a trend toward partial mediation of the choline effect on recognition memory. CONCLUSIONS: High-dose choline supplementation during pregnancy mitigated PAE-related regional volume reductions, with larger volumes associated with improved 12-month recognition memory. These results provide the first evidence that choline may be neuroprotective against PAE-related brain structural deficits in humans.

Alcohol-Related Alterations in Placental Imprinted Gene Expression in Humans Mediate Effects of Prenatal Alcohol Exposure on Postnatal Growth.

BACKGROUND: A growing body of evidence in animal models has implicated alcohol-induced alterations in epigenetic programming as an important mechanism in fetal alcohol spectrum disorders (FASD). Imprinted genes, a subset of epigenetically regulated genes that are sensitive to the prenatal environment, are chiefly involved in growth and neurobehavior. We tested the hypothesis that alterations in placental imprinted gene expression mediate fetal alcohol growth restriction. METHODS: Placental expression of 109 genes previously shown to be imprinted and expressed in the placenta was assessed using the NanoString™ nCounter Analysis System in flash-frozen samples from 34 heavy drinkers and 31 control women in Cape Town, South Africa, from whom prospective pregnancy alcohol consumption data had been obtained. Length/height, weight, and head circumference were measured at 6.5 and 12 months and at an FASD diagnostic clinic (at ages 1.1 to 4.6 years) that we organized. Imprinted gene expression between exposed and control placentas was compared using the limma R package. The relation of alcohol exposure to World Health Organization length-for-age z-scores was examined before and after inclusion of expression for each alcohol-related imprinted gene, using hierarchical mixed regression models with repeated measures. RESULTS: Heavy drinkers averaged 8 standard drinks on 2 to 3 days/wk (vs. 0 for controls). Prenatal alcohol exposure was associated with smaller length/height and weight during the postnatal period. Heavy exposure was related to alterations in expression of 11 of 93 expressed imprinted genes, including increased expression of 5 genes found to be negatively associated with growth and decreased expression of 3 genes positively associated with growth. Alcohol-related alterations in expression of 5 genes statistically mediated the effect of prenatal alcohol exposure on length. CONCLUSIONS: These findings identify alcohol-related alterations in placental imprinted gene expression as potential biomarkers of adverse effect in FASD and suggest that these alterations may play a mechanistic role in fetal alcohol growth restriction. Future studies are needed to determine whether alterations in imprinted gene expression also mediate FASD neurobehavioral deficits and whether such alterations are amenable to intervention.

Feasibility and Acceptability of Maternal Choline Supplementation in Heavy Drinking Pregnant Women: A Randomized, Double-Blind, Placebo-Controlled Clinical Trial.

BACKGROUND: Choline, an essential nutrient, serves as a methyl-group donor for DNA methylation and is a constituent of the neurotransmitter acetylcholine and a precursor to major components of cell membranes. Findings from animal studies suggest that choline supplementation during pregnancy can mitigate adverse effects of prenatal alcohol exposure on growth and neurocognitive function. We conducted a randomized, double-blind exploratory trial to examine feasibility and acceptability of a choline supplementation intervention during pregnancy. METHODS: Seventy heavy drinkers, recruited in mid-pregnancy, were randomly assigned to receive a daily oral dose of 2 g of choline or a placebo from time of enrollment until delivery. Each dose consisted of an individually wrapped packet of powder that, when mixed with water, produced a sweet tasting grape-flavored drink. Adherence was assessed by collecting used and unused drink packets on a monthly basis and tabulating the number used. Side effects were assessed in monthly interviews. Blood samples obtained at enrollment and at 4 and 12 weeks after randomization were assayed for plasma choline concentration. RESULTS: Adherence was good-to-excellent (median doses taken = 74.0%; interquartile range = 53.9 to 88.7%) and was not related to a range of sociodemographic characteristics or to alcohol consumption ascertained using a timeline follow-back interview. By 4 weeks, plasma choline concentrations were significantly higher in the choline supplementation than the placebo arm, and this group difference continued to be evident at 12 weeks. The only side effect was a small increase in nausea/dyspepsia. No effects were seen for diarrhea, vomiting, muscle stiffness, blood pressure, or body odor changes. CONCLUSIONS: This study demonstrated that a choline supplementation program with very heavy drinkers during pregnancy is feasible even among highly disadvantaged, poorly educated women. The broad acceptability of this intervention is indicated by our finding that adherence was not related to maternal education, intellectual function, depression, nutritional status, or alcohol use.

Efficacy of Maternal Choline Supplementation During Pregnancy in Mitigating Adverse Effects of Prenatal Alcohol Exposure on Growth and Cognitive Function: A Randomized, Double-Blind, Placebo-Controlled Clinical Trial.

BACKGROUND: We recently demonstrated the acceptability and feasibility of a randomized, double-blind choline supplementation intervention for heavy drinking women during pregnancy. In this study, we report our results relating to the efficacy of this intervention in mitigating adverse effects of prenatal alcohol exposure (PAE) on infant growth and cognitive function. METHODS: Sixty-nine Cape Coloured (mixed ancestry) heavy drinkers in Cape Town, South Africa, recruited in mid-pregnancy, were randomly assigned to receive a daily oral dose of either 2 g of choline or placebo from time of enrollment until delivery. Each dose consisted of an individually wrapped packet of powder that, when mixed with water, produced a sweet tasting grape-flavored drink. The primary outcome, eyeblink conditioning (EBC), was assessed at 6.5 months. Somatic growth was measured at birth, 6.5, and 12 months, recognition memory and processing speed on the Fagan Test of Infant Intelligence, at 6.5 and 12 months. RESULTS: Infants born to choline-treated mothers were more likely to meet criterion for conditioning on EBC than the placebo group. Moreover, within the choline arm, degree of maternal adherence to the supplementation protocol strongly predicted EBC performance. Both groups were small at birth, but choline-treated infants showed considerable catch-up growth in weight and head circumference at 6.5 and 12 months. At 12 months, the infants in the choline treatment arm had higher novelty preference scores, indicating better visual recognition memory. CONCLUSIONS: This exploratory study is the first to provide evidence that a high dose of choline administered early in pregnancy can mitigate adverse effects of heavy PAE on EBC, postnatal growth, and cognition in human infants. These findings are consistent with studies of alcohol-exposed animals that have demonstrated beneficial effects of choline supplementation on classical conditioning, learning, and memory.

Development and validation of a quantitative choline food frequency questionnaire for use with drinking and non-drinking pregnant women in Cape Town, South Africa.

BACKGROUND: Although animal and human studies have demonstrated interactions between dietary choline and fetal alcohol spectrum disorders, dietary choline deficiency in pregnancy is common in the US and worldwide. We sought to develop and validate a quantitative food frequency questionnaire (QFFQ) to estimate usual daily choline intake in pregnant mothers. METHODS: A panel of nutrition experts developed a Choline-QFFQ food item list, including sources with high choline content and the most commonly consumed choline-containing foods in the target population. A data base for choline content of each item was compiled. For reliability and validity testing in a prospective longitudinal cohort, 123 heavy drinking Cape Coloured pregnant women and 83 abstaining/light-drinking controls were recruited at their first antenatal clinic visit. At 3 prenatal study visits, each gravida was interviewed about alcohol, smoking, and drug use, and administered a 24-hour recall interview and the Choline-QFFQ. RESULTS: Across all visits and assessments, > 78% of heavy drinkers and controls reported choline intake below the Dietary Reference Intakes adequate intake level (450 mg/day). Women reported a decrease in choline intake over time on the QFFQ. Reliability of the QFFQ across visits was good-to-acceptable for 2 of 4 group-level tests and 4 of 5 individual-level tests for both drinkers and controls. When compared with 24-hr recall data, validity of the QFFQ was good-to-acceptable for 3 of 4 individual-level tests and 3 of 5 group-level tests. For controls, validity was good-to-acceptable for all 4 individual-level tests and all 5 group-level tests. CONCLUSIONS: To our knowledge, this is the first quantitative choline food frequency screening questionnaire to be developed and validated for use with both heavy and non-drinking pregnant women and the first to be used in the Cape Coloured community in South Africa. Given the high prevalence of inadequate choline intake and the growing evidence that maternal choline supplementation can mitigate some of the adverse effects of prenatal alcohol exposure, this tool may be useful for both research and future clinical outreach programs.

Maternal Alcohol Use and Nutrition During Pregnancy: Diet and Anthropometry.

BACKGROUND: Despite known risks of prenatal nutritional deficiencies and studies documenting increased prevalence of poor dietary intake among nonpregnant alcohol abusers, the nutritional status of heavy drinking pregnant women remains largely unstudied. Animal models have found interactions between prenatal ethanol exposure and micronutrients, such as choline, folate, B12, and iron, and human studies have reported that lower maternal weight and body mass confer increased fetal alcohol-related risk. METHODS: One hundred and twenty-three heavy drinking Cape Coloured pregnant women and 83 abstaining controls were recruited at their first antenatal clinic visit. At 3 prenatal study visits, each gravida was interviewed about alcohol, smoking, and drug use and weight, height, and arm skinfolds were measured. Dietary intakes of energy, protein, fat, and major micronutrients were assessed from three 24-hour recall interviews. RESULTS: The majority of women gained less than the recommended 0.42 kg/wk during pregnancy. Whereas methamphetamine use was associated with smaller biceps skinfolds, an indicator of body fat, alcohol consumption was not related to any anthropometric indicator. Alcohol was related to higher intake of phosphorus, choline, and vitamins B12 and D. Alcohol, cigarette, and methamphetamine use were related to lower vitamin C intake. Insufficient intake was reported by >85% of women for 10 of 22 key nutrients, and >50% for an additional 3 nutrients. CONCLUSIONS: Alcohol consumption during pregnancy was not associated with meaningful changes in diet or anthropometric measures in this population, suggesting that poor nutrition among drinkers does not confound the extensively reported effects of prenatal alcohol exposure on growth and neurobehavior. The poor gestational weight gain and high rates of insufficient intake for several nutrients in both the alcohol-exposed and control groups are also of public health importance.

Heavy Prenatal Alcohol Exposure is Related to Smaller Corpus Callosum in Newborn MRI Scans.

BACKGROUND: Magnetic resonance imaging (MRI) studies have consistently demonstrated disproportionately smaller corpus callosa in individuals with a history of prenatal alcohol exposure (PAE) but have not previously examined the feasibility of detecting this effect in infants. Tissue segmentation of the newborn brain is challenging because analysis techniques developed for the adult brain are not directly transferable, and segmentation for cerebral morphometry is difficult in neonates, due to the latter's incomplete myelination. This study is the first to use volumetric structural MRI to investigate PAE effects in newborns using manual tracing and to examine the cross-sectional area of the corpus callosum (CC). METHODS: Forty-three nonsedated infants born to 32 Cape Coloured heavy drinkers and 11 controls recruited prospectively during pregnancy were scanned using a custom-designed birdcage coil for infants, which increases signal-to-noise ratio almost 2-fold compared to the standard head coil. Alcohol use was ascertained prospectively during pregnancy, and fetal alcohol spectrum disorders diagnosis was conducted by expert dysmorphologists. Data were acquired using a multi-echo FLASH protocol adapted for newborns, and a knowledge-based procedure was used to hand-segment the neonatal brains. RESULTS: CC was disproportionately smaller in alcohol-exposed neonates than controls after controlling for intracranial volume. By contrast, CC area was unrelated to infant sex, gestational age, age at scan, or maternal smoking, marijuana, or methamphetamine use during pregnancy. CONCLUSIONS: Given that midline craniofacial anomalies have been recognized as a hallmark of fetal alcohol syndrome in humans and animal models since this syndrome was first identified, the CC deficit identified here in newborns may support early identification of a range of midline structural impairments. Smaller CC during the newborn period may provide an early indicator of fetal alcohol-related cognitive deficits that have been linked to this critically important brain structure in childhood and adolescence.

Alcohol, Methamphetamine, and Marijuana Exposure Have Distinct Effects on the Human Placenta.

BACKGROUND: Animal studies have demonstrated adverse effects of prenatal alcohol exposure on placental development, but few studies have examined these effects in humans. Little is known about effects of prenatal exposure to methamphetamine, marijuana, and cigarette smoking on placental development. METHODS: Placentas were collected from 103 Cape Coloured (mixed ancestry) pregnant women recruited at their first antenatal clinic visit in Cape Town, South Africa. Sixty-six heavy drinkers and 37 nondrinkers were interviewed about their alcohol, cigarette smoking, and drug use at 3 antenatal visits. A senior pathologist, blinded to exposure status, performed comprehensive pathology examinations on each placenta using a standardized protocol. In multivariable regression models, effects of prenatal exposure were examined on placental size, structure, and presence of infections and meconium. RESULTS: Drinkers reported a binge pattern of heavy drinking, averaging 8.0 drinks/occasion across pregnancy on 1.4 d/wk. 79.6% smoked cigarettes; 22.3% used marijuana; and 17.5% used methamphetamine. Alcohol exposure was related to decreased placental weight and a smaller placenta-to-birthweight ratio. By contrast, methamphetamine was associated with larger placental weight and a larger placenta-to-birthweight ratio. Marijuana was also associated with larger placental weight. Alcohol exposure was associated with increased risk of placental hemorrhage. Prenatal alcohol, drug, and cigarette use were not associated with chorioamnionitis, villitis, deciduitis, or maternal vascular underperfusion. Alcohol and cigarette smoking were associated with a decreased risk of intrauterine passing of meconium, a sign of acute fetal stress and/or hypoxia; methamphetamine, with an increased risk. CONCLUSIONS: This is the first human study to show that alcohol, methamphetamine, and marijuana were associated with distinct patterns of pathology, suggesting different mechanisms mediating their effects on placental development. Given the growing body of evidence linking placental abnormalities to neurodevelopmental deficits, these findings may be important in the long-term teratogenic effects of prenatal alcohol and drug exposure.

Infant emotional withdrawal: a precursor of affective and cognitive disturbance in fetal alcohol spectrum disorders.

BACKGROUND: Our aim was to test the hypothesis that emotional withdrawal is an early indicator of affective disorder in infants heavily exposed prenatally to alcohol, which is independent of alcohol-related effects on mother-infant interaction and temperament and discriminated between children later diagnosed with fetal alcohol syndrome (FAS) and partial FAS (PFAS) and predicted cognitive and affective outcomes at 5 and 9 years. METHODS: The sample consisted of Cape Coloured (mixed ancestry) infants, whose mothers were interviewed during pregnancy regarding their alcohol consumption using a timeline follow-back approach. Infant emotional withdrawal (n = 85) was assessed on the Alarm Distress Baby Scale at 6.5 months. Mother-infant interaction was evaluated from video recordings during free play and infant feeding at 6.5 months (n = 127). Infant temperament was assessed by maternal report on the EAS Temperament Survey at 13 months (n = 119). Sociodemographic and psychological correlates of maternal alcohol use and infant iron deficiency were examined as potential confounders. The children were diagnosed for FAS/PFAS by expert dysmorphologists at 5 years, cognitive and affective function at 5 and 9 years. RESULTS: Prenatal alcohol exposure was associated with increased infant emotional withdrawal and decreased activity, but unrelated to mother-infant interaction or any other temperament measures. Children later diagnosed with FAS and PFAS at 5 years exhibited more emotional withdrawal and less responsivity and activity as infants. Infant withdrawal, responsivity, quality of interaction, and maternal sensitivity also predicted poorer IQ and affective response at 5 and 9 years. When all 4 infant affective measures were examined simultaneously in a regression analysis, only infant emotional withdrawal persisted as a significant predictor of 9-year IQ. CONCLUSIONS: This study is the first to document a direct effect of fetal alcohol exposure on emotional withdrawal in infancy. These data link prenatal alcohol to a specific aspect of infant affective function not attributable to mother-infant interaction, infant temperament, or other socioemotional aspects of the infant's environment and identify infant emotional withdrawal as an early indicator of affective disturbance, particularly in children later diagnosed with FAS and PFAS.

Effects of prenatal alcohol exposure on testosterone and pubertal development.

BACKGROUND: Animal models have demonstrated fetal alcohol-related disruptions in neuroendocrine function in the hypothalamic-pituitary-gonadal axis and downstream effects on pubertal development and sexual behavior in males and females, but little is known about these effects in humans. This study examined whether prenatal alcohol exposure is associated with alterations in testosterone during adolescence and whether it affects timing of pubertal development. METHODS: The sample consisted of 265 African American adolescents from the Detroit Longitudinal Cohort Study for whom testosterone and/or pubertal development data were available. Subjects were offspring of women recruited at their first prenatal clinic visit to over represent moderate-to-heavy alcohol use, including a 5% random sample of low-level drinkers/abstainers. Mothers were interviewed at every prenatal visit about their alcohol consumption using a timeline follow-back approach and about their smoking and drug use and sociodemographic factors. At age 14 years, adolescents provided salivary samples, which were analyzed for testosterone (pg/ml), self-reported Tanner stages for pubertal development, and age at menarche (females). RESULTS: Prenatal alcohol exposure was related to elevated testosterone concentrations for males and females but not to changes in Tanner stages or age at menarche, after controlling for confounders. In regression models stratified by alcohol exposure, the expected relation between testosterone and pubic hair development was seen among males with light-to-no prenatal alcohol exposure, but not among those with moderate-to-heavy prenatal alcohol exposure. This interaction between testosterone and prenatal alcohol exposure was confirmed in multivariable models including an alcohol exposure group × testosterone interaction term and potential confounders. CONCLUSIONS: This study is the first to show a relation between prenatal alcohol exposure and increased testosterone during adolescence and evidence of decreased testosterone responsiveness in tissues related to pubertal development in humans. Further studies examining androgen receptor expression and other hormonal and cellular factors affecting pubertal development may reveal important mechanisms underlying these teratogenic effects of alcohol exposure.

RNA-seq analysis reveals prenatal alcohol exposure is associated with placental inflammatory cells and gene expression.

BACKGROUND: Fetal alcohol spectrum disorders (FASD) are the most common preventable cause of birth defects and neurodevelopmental disorders worldwide. The placenta is the crucial interface between mother and fetus. Prenatal alcohol exposure (PAE) has been shown to alter placental structure and expression of genes in bulk placental tissue samples, but prior studies have not examined effects on placental cell-type composition or taken cell-type into consideration in transcriptome analyses. METHODS: We leveraged an existent placenta single-cell RNA-seq dataset to perform cell-type deconvolution of bulk placental RNA-seq data from 35 heavy drinking pregnant women and 33 controls in a prospective birth cohort in Cape Town, South Africa. We used bivariate analyses and multivariable adjusted linear regression models to assess the relation of PAE on inferred placental cell-type proportions. We also examined differential expression of inflammatory response genes and PAE, using multivariable adjusted linear models. RESULTS: Deconvolution analyses showed heterogeneous placenta cell-type composition in which stromal (27 %), endothelial (26 %) and cytotrophoblasts (18 %) were the predominant cell-types. PAE around conception was associated with a higher proportion of Hofbauer cells (B = 0.51, p = 0.035) in linear models adjusted for maternal age, infant sex, and gestational age. Among the 652 inflammatory genes examined, 35 were differential expressed in alcohol exposed placentas (FDR p < 0.05). CONCLUSIONS: Our findings suggest that heavy alcohol exposure during pregnancy can influence the proportion of fetal placental villi macrophages (Hofbauer cells) and increased expression of inflammatory genes. Future studies are needed to further characterize these effects and to assess the potential functional roles of placental inflammation in FASD.

Prenatal alcohol exposure is associated with changes in placental gene co-expression networks.

Alcohol consumption during pregnancy can result in a range of adverse postnatal outcomes among exposed children. However, identifying at-risk children is challenging given the difficulty to confirm prenatal alcohol exposure and the lack of early diagnostic tools. Placental surveys present an important opportunity to uncover early biomarkers to identify those at risk. Here, we report the first transcriptome-wide evaluation to comprehensively evaluate human placental pathways altered by fetal alcohol exposure. In a prospective longitudinal birth cohort in Cape Town, South Africa, we performed bulk tissue RNAseq in placenta samples from 32 women reporting heavy drinking during pregnancy and 30 abstainers/light drinkers. Weighted gene co-expression network analysis (WGCNA) and differential gene expression analysis were performed to assess associations between fetal alcohol exposure and placental gene expression patterns at a network-wide and single gene level, respectively. The results revealed altered expression in genes related to erythropoiesis and angiogenesis, which are implicated in established postnatal phenotypes related to alcohol exposure, including disruptions in iron homeostasis, growth, and neurodevelopment. The reported findings provide insights into the molecular pathways affected by prenatal alcohol exposure and highlight the potential of placental biomarkers for detecting and understanding the effects of alcohol on fetal development.

Genetic admixture predictors of fetal alcohol spectrum disorders (FASD) in the South African Cape Coloured population.

Ancestrally admixed populations are underrepresented in genetic studies of complex diseases, which are still dominated by European-descent populations. This is relevant not only from a representation standpoint but also because of admixed populations' unique features, including being enriched for rare variants, for which effect sizes are disproportionately larger than common polymorphisms. Furthermore, results from these populations may be generalizable to other populations. The South African Cape Coloured (SACC) population is genetically admixed, with one of the highest prevalences of fetal alcohol spectrum disorders (FASD) worldwide. We profiled its admixture and examined associations between ancestry profiles and FASD outcomes using two longitudinal birth cohorts ( N =308 mothers, 280 children) designed to examine effects of prenatal alcohol exposure on development. Participants were genotyped via MEGA-ex array to capture common and rare variants. Rare variants were overrepresented in our SACC cohorts, with numerous polymorphisms being monomorphic in other reference populations (e.g., ∼30,000 and ∼221,000 variants in gnomAD European and Asian populations, respectively). The cohorts showed global African (51%; Bantu and San); European (26%; Northern/Western); South Asian (18%); and East Asian (5%; largely Southern regions) ancestries. The cohorts exhibited high rates of homozygosity (6%), with regions of homozygosity harboring more deleterious variants when lying within African local-ancestry genomic segments. Both maternal and child ancestry profiles were associated with FASD risk and altered severity of prenatal alcohol exposure-related cognitive deficits in the child. Our findings indicate that the SACC population may be a valuable asset to identify novel disease-associated genetic loci for FASD and other diseases.

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.

Commentary on Day and colleagues : the association between prenatal alcohol exposure and behavior at 22 years of age--adverse effects of risky patterns of drinking among low to moderate alcohol-using pregnant women.

Day and colleagues have presented the first data showing that the behavioral effects of low to moderate prenatal alcohol exposure seen in childhood and adolescence persist into adulthood. Using the Achenbach Adult Self-Report, they found dose-dependent effects of prenatal exposure on internalizing, externalizing, and attention problems that persist in young adults and, thus, appear to be permanent. To date, few studies have attempted to identify thresholds at which prenatal alcohol exposure is harmful, although the animal literature suggests that even 1 to 2 binge episodes can result in adverse effects in the offspring. Four prospective longitudinal studies have reported adverse effects at what can be characterized as moderate exposure levels based on NIAAA criteria, but moderate drinking women often concentrate their alcohol use on 1 to 2 days per week, thereby engaging in binge drinking. In this study, binge drinking was not a strong predictor of adverse outcome when average daily dose was held constant, a conclusion that the authors note runs "counter to studies that have reported that binge drinking has a greater effect." This inconsistency may be due to the difficulty of allocating variance that is shared (overlapping) between average daily dose and binge drinking (i.e., dose/occasion). Data from laboratory animal studies, in which dosage can be manipulated experimentally, demonstrate that a higher dose per occasion, the key feature of binge drinking, leads to more severe adverse effects. Day and colleagues' findings of adverse effects at low levels of exposure provides clear evidence that there is no safe level of drinking during pregnancy and that, even at low levels, drinking results in irreversible behavioral impairment. On the other hand, given the evidence from the animal and most human studies, it is important for all women who drink during pregnancy, even at light to moderate levels, to recognize that minimizing their intake per occasion and refraining from binge drinking can reduce risk to the fetus.

Fetal alcohol-related growth restriction from birth through young adulthood and moderating effects of maternal prepregnancy weight.

BACKGROUND: Fetal alcohol-related growth restriction persists through infancy, but its impact later in life is less clear. Animal studies have demonstrated important roles for maternal nutrition in fetal alcohol spectrum disorders, but the impact of prenatal maternal body composition has not been studied in humans. This study examined the effects of prenatal alcohol exposure on longitudinal growth from birth through young adulthood and the degree to which maternal weight and body mass index (BMI) moderate these effects. METHODS: Nearly 480 mothers were recruited at their first prenatal clinic visit to overrepresent moderate-to-heavy use of alcohol during pregnancy, including a 5% random sample of low-level drinkers and abstainers. They were interviewed at every prenatal visit about their alcohol consumption using a timeline follow-back approach. Their children were examined for weight, length/height, and head circumference at birth, 6.5 and 13 months, and 7.5, 14, and 19 years. RESULTS: In multiple regression models with repeated measures (adjusted for confounders), prenatal alcohol exposure was associated with longitudinal reductions in weight, height, and weight-for-length/BMI that were largely determined at birth. At low-to-moderate levels of exposure, these effects were more severe in infancy than in later childhood. By contrast, effects persisted among children whose mothers drank at least monthly and among those born to women with alcohol abuse and/or dependence who had consumed ≥ 4 drinks/occasion. In addition, effects on weight, height, and head circumference were markedly stronger among children born to mothers with lower prepregnancy weight. CONCLUSIONS: These findings confirm prior studies demonstrating alcohol-related reductions in weight, height, weight-for-height/BMI, and head circumference that persist through young adulthood. Stronger effects were seen among children born to mothers with smaller prepregnancy weight, which may have been because of attainment of higher blood alcohol concentrations in smaller mothers for a given amount of alcohol intake or to increased vulnerability in infants born to women with poorer nutrition.

Fetal Alcohol-Related Postnatal Growth Restriction Is Independent of Infant Feeding Practices and Postnatal Alcohol Exposure in a Prospective South African Birth Cohort.

Prenatal alcohol exposure (PAE) causes growth restriction that worsens in the first year of life. However, the roles of postnatal nutrition in fetal alcohol growth restriction and the impact of postnatal alcohol exposure via breastmilk on growth remain unknown. We aimed to compare infant feeding practices during the first 6.5 months of life between heavy drinkers and abstainers/light drinkers, to examine whether these practices play confounding roles in fetal alcohol growth restriction, and to determine the impact of postnatal alcohol exposure via breastmilk on growth. Eighty-seven heavy-drinking pregnant women and 71 abstainers/light drinkers (controls) were recruited prenatally from antenatal clinics in Cape Town, South Africa. Demographic background and alcohol, cigarette, marijuana, and methamphetamine use during pregnancy were assessed pre- and postnatally. Infant feeding practices were assessed at 6.5 months postpartum using the USDA Infant Feeding Questionnaire. Infant weight, length, and head circumference were measured at 2 weeks, 6.5 and 12 months, and 5 years. Neither prenatal nor postnatal alcohol consumption was related to the duration of breastfeeding, exclusive breastfeeding, exclusive formula, or mixed feeding. Complementary feeding practices were remarkably similar between exposure groups. PAE was related to all postnatal anthropometry measures at all age points, independent of infant feeding practices. Postnatal alcohol exposure via breastmilk was unrelated to any anthropometry outcome after control for PAE. In conclusion, fetal alcohol-related postnatal growth restriction was not attributable to differences in postnatal infant feeding practices or postnatal alcohol exposure and is thus likely a direct teratogenic effect of PAE.