Not fortifying flour with folic acid is a "public health failure" for the UK, say the researchers.
It is important that women get enough folic acid during pregnancy; the vitamin is important for healthy development of the fetus, reducing the risk of neural tube defects (NTDs) such as spina bifida and anencephaly.
According to the US Public Health Service, the Centers for Disease Control and Prevention (CDC) and the UK's Department of Health, all women of childbearing age should take 400 micrograms (mcg) of folic acid a day.
It is difficult for such women to get a high enough folic acid intake from dietary modifications alone. As such, the use of folic acid supplements or consumption of foods fortified with the vitamin is advised.
In 1998, the US Food and Drug Administration (FDA) required all manufacturers to fortify flour - as well as cereals, pasta, rice and other grain products - with folic acid, a program that has been estimated to increase mean folic acid intake in the US by around 200 mcg daily. Such a requirement is also present in 77 other countries - but the UK is not one.
In this latest study - published in the Archives of Disease in Childhood - Prof. Joan Morris, of Queen Mary University of London in the UK, and colleagues set out to estimate how many cases of neural tube defects could have been prevented if the UK had adopted fortification of flour with folic acid since 1998, as has been done in the US.
Prevalence of NTDs could have been reduced by 21%
To do so, Prof. Morris and colleagues analyzed data from the British Isles Network of Congenital Anomaly Registers (BINOCAR) to assess the number of NTDs and associated terminations of pregnancy that occurred in the UK between 1991-2012.
The team estimated the number of pregnancies with an NTD that could have been avoided with fortification of flour with folic acid, based on previous estimates that such fortification provides women of childbearing age with an additional 200 mcg daily.
The researchers identified a prevalence of pregnancies with an NTD of 1.28 per 1,000 births between 1991-2012, and 81% of these pregnancies were terminated.
While there was a 23% reduction in prevalence of pregnancies with NTDs in the US between 1998-2012 - after mandatory fortification of flour with folic acid was introduced - there was no significant change in the UK during the 14-year period.
The researchers also found no significant changes in UK prevalence of spina bifida, anencephaly with or without spina bifida or encephalocele when analyzing each condition separately.
The team estimated that 2,014 fewer pregnancies with an NTD could have been avoided between 1998-2012 if the UK had adopted the same fortification policy, representing a possible fall in NTD prevalence of 21% in the 14-year period.
Unless the UK adopt mandatory fortification of flour with folic acid, there will be an additional 150 pregnancies with an NTD each year, around half of which will be due to spina bifida without anencephaly, according to the researchers.
What is more, if such pregnancies are not terminated, almost all would result in the birth of severely disabled children.
Failure to fortify a 'public health failure'
The team compares this current situation with the thalidomide epidemic - a drug that caused around 500 people in the UK to be born disabled.
"Justifiably, steps were introduced to immediately halt the epidemic, and regulatory precautions were introduced to avoid another similar epidemic," they note. "Unfortunately, no such sense of urgency has been applied to the prevention of spina bifida."
The researchers add:
"It is illogical to take preventive public health action to avoid a drug-induced congenital anomaly, but to largely ignore action in relation to a congenital anomaly which can be prevented by vitamin fortification of flour, when the failure to act has resulted in, and continues to result in, many more serious cases.
It is a public health failure that Britain has not implemented the fortification of flour with folic acid for the prevention of spina bifida and other NTDs."
It seems the UK Government is taking note of calls to adopt the mandatory fortification policy, however. Last year, the Department of Health revealed they are "currently considering the case of mandatory fortification of flour with folic acid and will reach a decision in the light of new data from the National Diet and Nutrition Survey."
Folic acid may not only be effective for reducing the risk of NTDs; a study reported by Medical News Today earlier this year found that for people with high blood pressure, folic acid may reduce the risk of first stroke.