UK experts are backing the call for flour to be fortified with folic acid - a move which they say would have prevented around 2,000 cases of serious birth defects since 1998.
The failure to fortify flour has caused serious disabilities, including spina bifida, and resulted in terminations and stillbirths, their study said.
The US and 77 other countries already have a policy in place.
The Department of Health said it was currently considering the matter.
This follows the Scientific Advisory Committee on Nutrition recently saying it was in favour of folic add being added to flour for bread in the UK.
Folic acid is found naturally in some foods, such as green vegetables, nuts and granary bread.
It is added to some breakfast cereals, but it is very difficult for pregnant women to get enough from diet alone.
That is why in 1992, the Department of Health in England recommended that women take folic acid supplements before pregnancy to reduce their risk of having a baby with a neural tube defect (NTD) - which involve defects of the brain, spine or spinal cord.
But recent research shows that only 28% of pregnant women take them at the correct time.
However the government has so far been reluctant to force manufacturers to add folic acid to all bread.
This study, published in the Archives of Disease in Childhood, said the current policy was not working and the UK should be following the example of the US in fortifying flour with folic acid.
The US has seen a 23% fall in pregnancies with neural tube defects since the policy was introduced in 1998.
The researchers estimated that a similar policy in the UK would have prevented 1,798 pregnancies with NTD in England and Wales, 152 in Scotland and 64 in Northern Ireland over a 14-year period up to 2012.
This equates to a fall of 21% in pregnancies with neural tube defects over that period.
While most of the NTD pregnancies are terminated, around 75 babies a year are born with serious disabilities.
The research team, led by Prof Joan Morris from the Wolfson Institute of Preventative Medicine at Queen Mary University of London, said putting folic acid in flour was safe and could only be a good thing.
"Europe is the only region not to have a policy of fortifying flour with folic acid, despite evidence that it can cut the risk of neural tube defects by around 70%."
Reaching more women
Dr Alison Tedstone, chief nutritionist at Public Health England, said too many women had folic acid levels below the new World Health Organization recommendation for women entering pregnancy.
"This highlights the importance for pregnant women, and those trying or likely to get pregnant, of taking a daily folic acid supplement of 400 micrograms - before and up to the 12th week of pregnancy."
Prof Alan Cameron, vice president of clinical quality for the Royal College of Obstetricians and Gynaecologists, said: "Food fortification will reach women most at risk due to poor dietary habits or socio-economic status as well as those women who may not have planned their pregnancy."