It’s one of the great health debates: the hazards or benefits of small amounts of alcohol during pregnancy remains intensely contested.

But there is a “paucity of evidence” for either side to make an argument, according to a new meta-analysis published in the journal BMJ Open.

“Despite the distinction between light drinking and abstinence being the point of most tension and confusion for health professional and pregnant women and contributing to inconsistent guidance and advice now and in the past, our extensive review shows that this specific question is not being researched thorough enough, if at all,” they said. 

The University of Bristol researchers used the recently issued United Kingdom cutoff of 32 grams of alcohol per week as their starting point. That amounts to one pint of strong beer, or a medium size glass of white wine, per week.

They unearthed 4,680 studies from databases such as Medline, PsycINFO, Embase on Ovid, and the Cochrane Library. But based on screening, that trove was whittled down due to alcohol amounts, and other factors that didn’t fit their criteria. Over several steps, their scope was shrunk to just 26 studies, 24 that were prospective and two that were quasi-experimental in nature.

Birth weight, premature birth, and fetal alcohol syndrome features were among the criteria that were examined in those remaining studies.

Some small correlation was made between the light alcohol intake and being small at gestational age, and preterm birth – but the latter were not statistically significant. But the researchers simply found little if any correlation in the studies that made the cut.

Better safe than sorry, they conclude.

“As there was some evidence that even light prenatal alcohol consumption is associated with being (small for gestational age) and preterm delivery, guidance could advise abstention as a precautionary principle but should explain the paucity of evidence,” they write.

What is needed is further scientific studies – involving a variety of looks including comparisons between siblings and other controls, they add.

“Formulating advice on the basis of the current evidence is challenging because we are still building the full picture of what happens to the unborn baby when small amounts of alcohol reach the bloodstream or brain,” said Luisa Zuccolo, one of the co-authors of the study, in a Bristol release. “We wanted to give women the most up-to-date and reliable evidence in order to empower them to make an informed decision about drinking during pregnancy and balancing any possible risk with other factors in their lives.” 

“We found limited evidence for a causal role of light drinking in pregnancy, compared with abstaining on most of the outcomes examined,” they write. “Describing the paucity of current research and explaining that ‘absence of evidence is not evidence of absence’ appears warranted.”