Elizabeth Elliott

ALCOHOL consumption rates in Australian women of child-bearing age are high and the prevalence of harmful drinking patterns, including “binge” drinking, have increased over the past decade.

Alcohol is a known teratogen, which increases the risk of a range of fetal effects so women need a consistent message about alcohol consumption during pregnancy.

The best message is the one aligned with the Australian alcohol guidelines, which state: “for women who are pregnant or planning a pregnancy, not drinking is the safest option”.

However, it is important not to instil panic in women who have consumed alcohol during pregnancy, particularly when the alcohol was consumed inadvertently prior to pregnancy recognition.

But with heavy or binge drinkers the news does not look good.

A recent study in Pediatrics shows that heavy prenatal alcohol exposure in the first trimester increases the risk of some birth defects by more than fourfold.

About 3% of women in the study who consumed alcohol at heavy levels had a child with an alcohol-related birth defect (ARBD) compared with less than 1% of the referent group.

Although this indicates that the risk of harm to the individual is relatively low, it confirms that fetal exposure to teratogens such as alcohol should be avoided.

Data for the study came from a randomly selected, population-based cohort of non-Aboriginal women who gave birth to a live infant in Western Australia 1995‒97 (n = 4714).

The women were surveyed about a wide range of social factors and health behaviours, including alcohol use, smoking, and other drug use for the 3 months pre-pregnancy and separately for each trimester of pregnancy.

These data were then linked to data from the WA Birth Defects Registry (BDR).

Birth defects were reviewed and classified as alcohol-related — according to criteria in the United States Institute of Medicine (IOM) guidelines for an ARBD — by WA BDR director Professor Carol Bower, who was blinded to the prenatal alcohol exposure of study participants.

Birth defects attributable to other known causes (eg, chromosomal abnormalities, genetic disorders, or other recognised syndromes) were excluded.

Compared with women who abstained from alcohol throughout pregnancy, women consuming at heavy levels during the first trimester had a fourfold increased odds of an ARBD (adjusted OR, 4.6; 95% CI, 1.5‒14.3).

Heavy prenatal alcohol exposure was defined as more than seven standard drinks per week (standard drink = 10 g alcohol) including binge levels of consumption (five or more standard drinks per occasion).

No increase in risk was found for moderate (three to four drinks per occasion, up to seven drinks per week) or low (one to two per occasion and fewer than seven per week) alcohol consumption during the first trimester.

The IOM guidelines classify a wide range of birth defects as alcohol-related but these are based on studies of high-risk groups.

Only a few of these birth defects were present in this population-based cohort — primarily cardiac defects (ventricular and atrial septal defects and conotruncal heart defects) and renal defects (kidney aplasia/dysplasia/hypoplasia, ureteral duplications, horseshoe kidney) — and additional population-based studies are required to validate the current IOM guidelines.

Fetal exposure to heavy alcohol consumption in the first trimester has likely increased since these cohort data were collected, particularly as about half of pregnancies are unplanned.

As well as an increase in binge drinking, serves of alcohol are generally much larger than the standard drink classifications used in research studies, so it takes relatively few drinks to reach the classification of heavy drinking used in this study.

This study adds to the evidence that the medical profession needs to be “on message” when talking to patients who are pregnant or planning a pregnancy.

Professor Elizabeth J Elliott is professor of paediatrics and child health at the Sydney Medical School, University of Sydney; consultant paediatrician at The Children’s Hospital, Westmead; National Health and Medical Research Council (NHMRC) practitioner fellow; and director of the Australian Paediatric Surveillance Unit.

Dr Colleen M O’Leary is an NHMRC postdoctoral research fellow, National Drug Research Institute, Curtin University, and research associate at the Division of Population Sciences Telethon Institute for Child Health Research.

This article was written with assistance from Clinical Professor Carol Bower, NHMRC senior principle research fellow at the Division of Population Sciences Telethon Institute for Child Health Research Centre for Child Health Research, University of Western Australia and director of the Birth Defects Register, WA.

Posted 6 December 2010