The head of Scotland's food watchdog has said it is unlikely Scotland would be able to go it alone and add folic acid to flour products such as bread.
Ross Finnie of Food Standards Scotland said the evidence was clear that fortification could help prevent birth defects such as spina bifida.
However, he said that the current industry set-up meant it could only be achieved on a UK-wide basis.
The UK government said it was "carefully considering" the issue.
An estimated 85% of women do not take enough folic acid in their diet.
The NHS currently recommends that women trying to conceive a child should consume 400 micrograms of folic acid, also known as vitamin B9, a day.
The vitamin is already added to some spreads and breakfast cereals, but ministers at Westminster have so far resisted ruling that it should be added to flour.
Referring to the latest advice from the Scientific Advisory Committee on Nutrition (SACN), Mr Finnie said: "The scientific evidence has shown for some years now that this is an effective way of reducing the liability to neural tube defects.
"Scottish ministers have been in favour of that for many years now and what Food Standards were asked, having previously been asked for scientific advice, what we were asked this time was to see if there were practical ways of implementing the policy in Scotland alone.
"Unfortunately we discovered, and it's nobody's fault, but the way in which the flour and milling industries are structured, they are structured in a way that delivers effective and efficiently, from their point of view, flour across the United Kingdom.
"Trying to separate that out, such that you would have separate plants having fortification of folic acid for delivery just in Scotland, the costs associated with that were disproportionate to the effort that was required."
The Scottish government has previously stated its support for mandatory fortification amid concern about low folate levels in Scotland.
Mr Finnie said there was also broad support for the initiative in Wales and in Northern Ireland.
He said: "Curiously enough, Public Health England actually supports this measure, but there appears to be some political resistance in England against this."
A UK government spokeswoman said: "We recognise the risk of pregnancies and births affected by neural tube defects and are grateful to SACN for their review of the evidence of folic acid.
"Ministers will carefully consider SACN's conclusions and respond in due course."