Women who find out they are pregnant after already having drunk during early pregnancy, should avoid further drinking, but should be aware that it is unlikely in most cases that their baby has been affected.
Still, he said, "the message from the March of Dimes is: Don't drink alcohol if you're pregnant, trying to get pregnant or think you may be pregnant". 10% report drinking in the last 30 days with greater than 3% reporting to debauch in 2015 report by U.S. center for Disease Control and Prevention (CDC).
Still, most experts agree that even a small risk is still a serious risk when it comes to a child's health. How light alcohol exposure may affect a developing fetus is less clear.
From 26 studies, the team found that drinking up to four units a week while pregnant, on average, was associated with an eight per cent higher risk of having a small baby compared with drinking no alcohol.
But they strongly advised mothers-to-be to avoid alcohol as a precaution.
In the new review, researchers found very little evidence that light drinking in pregnancy causes harm to babies, including birth defects, developmental delay, behavioural problems and impaired intelligence.
There is a risk of cognitive and behavioral problems in children whose mothers regularly drank more than 2 standard units per day.
"There is no safe amount for any pregnant women to drink because it is different from one person to another", Grunebaum told Newsweek.
According to a report appeared in the Guardian, drinking in pregnancy is a fraught issue and causes much anxiety.
Senior Research Associate Dr. Loubaba Mamluk said: "In conclusion, we found limited evidence for a causal role of light drinking in pregnancy, compared with abstaining, on most of the outcomes examined".
Researchers stated: "Despite the distinction between light drinking and abstinence being the point of most tension, and confusion for health professionals 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 thoroughly enough, if at all".
"We were surprised that this very important topic was not researched as widely as expected", she said. The risks of minimal alcohol consumption should not be overemphasized. It has been hard to associate low levels of alcohol intake in pregnancy and harm, and this work confirms this.
It is known that quantity and frequency of use, particularly binging, does correlate with increased risk. Could a small glass of wine here or there pose risks to a baby's health? For example, one study didn't adjust its figures so it wouldn't be thrown off by factors such as high or low numbers of participants who smoked and were poor, but others did. "There are all sorts of non-risk-based beverages or ways to relax or express one's emotions that do not confer fetal or lifelong effects", she said.