Intrauterine exposure to alcohol and tobacco use and childhood IQ: findings from a parental-offspring comparison within the Avon Longitudinal Study of Parents and Children

Prenatal substance use, prenatal stress and offspring behavioural outcomes: considerations for future studies

BACKGROUND

Numerous studies have been conducted in which the most common forms of maternal substance use during pregnancy (smoking, drinking or using cannabis) and maternal stress during pregnancy and her offspring's developmental or behavioural outcome have been the focus of interest. These studies seem to suggest that any perturbation caused by maternal substance use or maternal stress during fetal development may have (enduring) effects on offspring behaviour. However, recent developments in research methodology used to examine these associations question whether these prenatal influences actually cause altered offspring outcomes.

AIMS

This review provides a short overview of previous studies in this field of research, some methodological issues particularly involved in studies that focus on the association between maternal substance use or stress during pregnancy and offspring's outcomes. Furthermore, it introduces several new approaches that have been applied recently to test these associations.

RESULTS

Studies that applied these designs to disentangle prenatal influences from associated or inherited factors consistently show an effect of prenatal substance use exposure on birth weight, but yield little evidence for causal effects on behaviour. In contrast, prenatal stress may have a causal effect on some aspects of behaviour, although only one study thus far has been able to differentiate heritable factors from environmental factors.

Prevalence and predictors of alcohol use in pregnancy and breastfeeding among Australian women

BACKGROUND

Previous research suggests that alcohol use during pregnancy and breastfeeding has a negative impact on birth and neonatal outcomes. No threshold for this effect has been determined. The aim of this study is to determine the prevalence and correlates of alcohol use in pregnancy and lactation in a large representative sample of Australian women.

METHOD

Data were used from a large representative sample of Australian women drawn from the 2007 National Drug Strategy Household Survey. A complex sampling framework was used to elicit prevalence estimates for alcohol use during pregnancy and lactation. A logistic regression analysis was used to determine the psychosocial characteristics associated with alcohol use during the perinatal period.

RESULTS

Alcohol use was reported by 29 percent of women who were pregnant in the past 12 months. In addition, 43 percent of women who were breastfeeding in the past 12 months reported alcohol use, whereas 36 percent of women who were both pregnant and breastfeeding in the past 12 months reported alcohol use. Most women (95%) reported a reduction in the quantity of their alcohol use while pregnant or breastfeeding. Older age was significantly associated with alcohol use in pregnancy, and also with alcohol use while breastfeeding (after controlling for other psychosocial characteristics). Higher educational attainment, and breastfeeding for more weeks in the past 12 months were significantly associated with alcohol use while breastfeeding, after controlling for confounding psychosocial factors.

CONCLUSIONS

More research is needed to ease uncertainty about "safe" levels of alcohol use during pregnancy and while breastfeeding. A high proportion of the sample reported alcohol use during pregnancy or lactation, despite uniform international government guidelines recommending that no alcohol should be consumed during the prenatal and postnatal periods. These results indicate that public health education campaigns about the risks of alcohol during these periods are needed.

Postnatal cadmium exposure, neurodevelopment, and blood pressure in children at 2, 5, and 7 years of age

BACKGROUND

Adverse health effects of cadmium in adults are well documented, but little is known about the neuropsychological effects of cadmium in children, and no studies of cadmium and blood pressure in children have been conducted.

OBJECTIVE

We examined the potential effects of low-level cadmium exposure on intelligence quotient, neuropsychological functions, behavior, and blood pressure among children, using blood cadmium as a measure of exposure.

METHODS

We used the data from a multicenter randomized clinical trial of lead-exposed children and analyzed blood cadmium concentrations using the whole blood samples collected when children were 2 years of age. We compared neuropsychological and behavioral scores at 2, 5, and 7 years of age by cadmium level and analyzed the relationship between blood cadmium levels at 2 years of age and systolic and diastolic blood pressure at 2, 5, and 7 years of age.

RESULTS

The average cadmium concentration of these children was 0.21 microg/L, lower than for adults in the National Health and Nutrition Examination Survey (NHANES), but comparable to concentrations in children < 3 years of age in NHANES. Except for the California Verbal Learning Test for Children, there were no differences in test scores among children in different cadmium categories. For children with detectable pretreatment blood cadmium, after adjusting for a variety of covariates, general linear model analyses showed that at none of the three age points was the coefficient of cadmium on Mental Development Index or IQ statistically significant. Spline regression analysis suggested that behavioral problem scores at 5 and 7 years of age tended to increase with increasing blood cadmium, but the trend was not significant. We found no significant associations between blood cadmium levels and blood pressure.

CONCLUSION

We found no significant associations between background blood cadmium levels at 2 years of age and neurodevelopmental end points and blood pressure at 2, 5, and 7 years of age. The neuropsychological or hypertensive effects from longer background exposures to cadmium need further study.

Alcohol consumption during pregnancy and its effects on neurodevelopment: what is known and what remains uncertain

It has been claimed that mothers' drinking during pregnancy may affect the neurodevelopment of around 1% of all children. If this is true, then prenatal alcohol exposure represents an important risk factor for neurodevelopmental problems, giving rise to a large burden of disability which could be potentially preventable. Evidence to support this idea has come from animal experiments and human observational studies. However, such findings need to be supported by more robust research designs. Because randomized controlled trials in this area are neither feasible nor ethical, suggestions are made for further research making more use of natural experiments.

Moderate use of alcohol, tobacco and cannabis during pregnancy: new approaches and update on research findings

Interest in fetal origins of adverse offspring outcomes has grown extensively in the last decade. This has resulted in many published studies focusing on exposure in utero to substances and human offspring outcomes. Exposure to maternal substance use in pregnancy is believed to be a preventable hazard, and is therefore a main issue for public health concern and policy. However, an important question in human studies remains whether prenatal substance use exposure has an aetiological role in pathways to adverse developmental and behavioural outcomes via teratological effects. Recent insights and developments in research methodology will aid the adequate and more refined testing of associations between prenatal substance use and offspring outcomes. In particular, novel approaches could assist in disentangling the exposure to substance effects from correlated risk factors. The purpose of this manuscript is therefore to provide an overview of methodological issues involved in studies that focus on the association between maternal substance use during pregnancy and offspring's outcomes, to describe novel approaches to test these associations, and present some examples of new and well-designed studies and discuss their findings.