Pregnant women who occasionally overindulge in a night of drinking may not be harming their fetuses but more evidence is needed to determine whether this is really the case, British researchers said on Wednesday.
A review of 14 studies also suggested children whose mothers binge drank throughout pregnancy may suffer learning problems later in life, prompting a call for further research to see if any links exist.
"Just because we haven't been able to find much evidence doesn't mean there is no effect," said Ron Gray, a clinical epidemiologist at the University of Oxford, who led the study. "Our view is there needs to be more research."
A number of studies have linked heavy drinking on a regular basis during pregnancy to stunted growth, birth defects and brain development problems.
Less clear is the effect of occasional binge drinking, which amounted to about 5 drinks in one session in the studies Gray and his team reviewed.
The researchers initially identified more than 3,500 scientific papers between 1970 and 2005 looking at pregnancy and alcohol, which they winnowed down to 14 focusing on binge drinking.
They found little substantive evidence binge drinking once in a while caused problems such as miscarriage, stillbirth, abnormal birth weight, or birth defects such as fetal alcohol syndrome.
But one study suggested binge drinking could damage brain development resulting in reduced verbal IQ, learning problems and poorer academic performance.
"However, this study only counted women as bingers if they binged throughout pregnancy, not just on a single occasion," the researchers wrote.
Animal studies have shown harmful effects from binge drinking, which means pregnant women should still take care no matter how much they consume, Gray said.
At the same time until researchers have more evidence, women who binge drink on occasion should not fret unnecessarily about potential harm they are causing to their fetuses, he added.
"When pregnant women report isolated episodes of binge-drinking in the absence of a consistently high daily alcohol intake, as is often the case, it is important to avoid inducing unnecessary anxiety as, at present, the evidence of risk seems minimal," the researchers wrote.