The effect of different alcohol drinking patterns in early to mid-pregnancy

Sir,

We read with interest the series of papers by Kesmodel et al.^1–5 concerning a cohort of 5-year-old children prenatally exposed to alcohol, and the major conclusion that small volumes of alcohol consumed occasionally may not present serious concern.

This broad epidemiological study has several methodological problems related to the collection of data on prenatal exposure. First, recruitment with regard to the pregnancy period was made retrospectively and was obtained by telephone, with a probable memory bias. In addition, participation was far from 100%, excluding perhaps mothers who were alcoholics or tee-totallers. Second, it has been demonstrated that questionnaires on the blame-attributing question of alcohol consumption during pregnancy are not reliable, because women do not tell the truth or are unaware of their real alcohol consumption.⁶ It has been demonstrated that mothers who drink deny, and mothers who admit do not remember correctly, as biomarkers in the meconium show that, in fact, zero alcohol was consumed.⁷ Therefore, we must conclude that mothers do not usually underreport, but misreport. As a consequence, the division of the groups of women into various drinking levels cannot be considered to be reliable, which, in turn, makes it impossible to draw conclusions from the outcomes of tests on the children.⁶ Finally, the amount of alcohol which reaches the fetus depends not only on the volume of consumed alcohol, but also on genetic or epigenetic factors, and on transplacental passage, as has been demonstrated in twin studies.⁸ Thus, human observational studies must be based on objective measurements of prenatal alcohol exposure, that is, on alcohol biomarkers in alternative matrices.⁶

There is clear evidence from animal studies and from human clinical observation that prenatal exposure to alcohol has deleterious effects, even in low doses, specifically on neurodevelopmental aspects. Clearer answers on the effects of alcohol on humans are to be expected from several currently ongoing follow-up studies of newborns whose exposure was measured on the basis of meconium alcohol biomarkers.⁹

We are concerned about the conclusions that professionals and the public may have drawn from this study, and we take exception to the conclusion that ‘small quantities consumed occasionally in pregnancy DO NOT APPEAR [our emphasis] to pose serious issues’. In this case, no evidence of harm does not mean evidence of no harm.