In The BMJ this week, experts discuss the evidence and current guidelines on the controversial topic of alcohol consumption during pregnancy.
"Alcohol is not essential to the health or well being of a pregnant woman and is known to be harmful to her baby," argue Mary Mather, a retired paediatrician, and Kate Wiles, a doctoral research fellow in obstetric medicine at Guys and St Thomas NHS Trust.
They say "the only ethical advice that can be given is complete abstinence from alcohol in pregnancy."
Infants can suffer from fetal alcohol syndrome, mental retardation, development and behavioural abnormalities, and low birth weight. But how and when fetal damage occurs is unknown and will vary according to each individual pregnancy, they explain.
"Pregnant women must know there is no evidence of a threshold level of alcohol consumption in pregnancy below which there can be certainty that exposure is safe," they argue. They also say that "current guidance flies in the face of evidence and international consensus," adding that these present a "contradictory, confusing barrage of mixed messages."
The Department of Health, NICE and the Royal College of Obstetricians and Gynaecologists (RCOG) make inconsistent suggestions on the number of alcohol units that are safe for pregnant women.
Furthermore, few pregnant women or healthcare professionals understand what a unit of alcohol means, and "choose to drink" is open to misinterpretation. Many pregnant women drink alcohol during pregnancy and put their babies at risk, they say.
Meanwhile, many countries including Canada, Denmark, Norway, Australia, Ireland, the Netherlands and Scotland advise against alcohol consumption completely.
Guidelines need to be clear, consistent and acknowledge that no evidence shows that alcohol consumption below a certain level is safe, they argue. "Until this is provided, pregnant women in England and Wales will remain unable to make an informed choice about their use of alcohol in pregnancy."
Patrick O-Brien, a consultant and honorary senior lecturer in obstetrics and gynaecology at University College London Hospital agrees that "we have produced a raft of conflicting guidance for women."
However, he says that "this is our failing, not theirs," and the solution is not to consequently advise pregnant women to abstain from alcohol consumption. Instead, "we need to resolve these inconsistencies, then present the evidence in a clear and unambiguous way."
Guidelines must also acknowledge that in some areas evidence cannot provide a definite answer, he adds. There is no robust evidence that drinking within advised limits after 12 weeks of pregnancy is harmful for the fetus, but there can never be a 100% guarantee that any lower limit is safe.
In addition, he says there is considerable uncertainty around the blurred edges of robust evidence on the effects of alcohol consumption on fetal development, and how many associated conditions can be reasonably attributed to alcohol use.
And again, instead of telling women to abstain because the evidence is not certain, healthcare professionals should explain the current evidence and its limitations, and help pregnant women to make a decision, he insists.
"If they perceive that we have been making value judgements on their behalf, or professing certainty where none exists, we are certain to lose their trust," he concludes.