Boozing while pregnant has been a hard “no” for years, but now scientists are claiming that light drinking could be harmless.

Moms-to-be who tip back a few glasses of wine a week might not endanger their unborn baby, a new study by the British Medical Journal suggests.

Researchers reviewed 5,000 studies and selected 26 that looked at the impact of light drinking —  the equivalent to about two pints of beer or two glasses of wine per week (32 grams of alcohol)  — compared with no alcohol at all. They looked closely at complications of pregnancy and birth characteristics such as miscarriage, premature birth and undersized babies, and longer term concerns like developmental delays and impaired behaviors. They found drinking up to 32g a week was associated with an 8% higher risk of having a small baby, compared with no drinking at all, and a 10% increased risk of premature birth. But there wasn’t much evidence proving a “safe limit” or “detrimental impact” of how much one should or shouldn’t drink.

“Women who have had a drink while pregnant should be reassured that they are unlikely to have caused their baby considerable harm, but if worried, they should discuss this with their GP or midwife,” Senior Research Associate Dr. Loubaba Mamluk said.

Recently, more women are drinking during pregnancy. One in 10 pregnant women reported drinking in the last 30 days, with more than 3% reporting to binge, in a 2015 report by the US Centers for Disease Control and Prevention (CDC).  

However, doctors have long warned that consuming any alcohol while pregnant can come with serious medical risks, such as the possibility of a miscarriage, stillbirth, or mental, physical or behavioral problems in the baby known as fetal alcohol spectrum disorders. And the American Academy of Pediatrics says no amount of alcohol should be considered safe.

This new BMJ study calls for more research on the effects of light drinking during pregnancy in order to figure out potential risks and find answers to how much alcohol could be okay to consume.

“As there was some evidence that even light prenatal alcohol consumption is associated with being underweight and preterm delivery, guidance could advise abstention as a precautionary principle,” said Mamluk.

The Institute of Medicine estimates the yearly societal cost of preterm birth at $26 billion in the United States.  And the average cost of medical care for a premature or low birth-weight baby for its first year of life is about $49,000, according the March of Dimes Foundation.

A study from 2010 published in the Journal of Epidemiology and Community Health found that children of mothers who drink one or two glasses of boozy drinks per week during pregnancy were not at an increased risk of behavioral or cognitive problems by age five. And in 2013, another study published by the BMJ Open found no proof that a mother-to-be drinking moderately during pregnancy had an adverse effect on her child’s neurological development at age 10.