Folic acid 'doubles twin chance'

Folic Acid is thought to protect against birth defects

Pregnant women who take folic acid supplements to guard against birth defects are twice as likely to have twins, say scientists.

Health experts recommend women take folic acid before and during pregnancy to reduce the risk of their unborn child developing spinal cord defects, such as spina bifida.

It would be disastrous to see these efforts undermined, and for women to stop taking the recommended dose

John Grounds

In the US, the compulsory addition of the supplement to breakfast cereals and wholemeal bread since 1998 has reduced the incidence of spina bifida by 19%.

The UK Government is now considering following the US lead.

But the Swedish scientist whose team carried out the new research has questioned whether the risk of taking folic acid might outweigh the benefit.

Twins are more likely to be premature, have low birth weights, and suffer from cerebral palsy.

However, previous research has suggested no link between folic acid and twins, and campaigners have warned it would be disastrous if women were scared into not taking the supplement.

Data

Dr Bengt Kallen, from the Tornblad Institute in Lund, and his team looked at records from the Swedish Medical Birth Registry, which has gathered data on the use of medicines by pregnant women since 1994, New Scientist magazine reports.

Folic acid is added to bread in the US

A total of 2,569 women had used folic acid supplements, according to the records.

Among these women, the rate of twin births was 2.8 per 100 individuals, compared with a rate of 1.5% for the general Swedish population.

Dr Kallen calculated that if 30% of 100,000 women in Sweden took folic acid supplements there would be 225 extra pairs of twins.

Many of these 450 babies would be premature, have a low birth weight, and be at increased risk of cerebral palsy. At most, only four or five spina bifida cases would be avoided.

The reason why folic acid increases the risk of twins is unclear.

Call for more research

Dr Kallen suspects the supplement may increase the possibility of multiple ovulation or implantation of more than one egg in the womb.

He wants to see more research carried out to evaluate the effects of folic acid tablets.

He said: "I think one should consider the pros and cons - especially in areas like Sweden with a low rate of spina bifida."

Two years ago a committee was appointed by the UK Government to explore the possibility of compulsorily adding folic acid to flour.

It concluded that adding 240 micrograms of folic acid to every 100 grams of flour could cut the number of babies born with neural-tube defects by 41%.

Oxford University professor Sir John Grimley Evans, who chaired the committee, said it was important to identify any risks that might result from taking extra folic acid.

He told New Scientist: "The more of these possible things we identify so that people can monitor them, the better."

However he stressed that more work had to be done to confirm that the link was genuine.

Efforts 'undermined'

Professor Richard Smithells carried out pioneering research 30 years ago which identified the protective qualities of folic acid.

He said there was no firm evidence that folic acid caused multiple births.

However, he added: "There is evidence that folic acid helps prevent a wide range of birth defects, including more than originally thought."

Professor Smithells' work was funded by the charity Action Research.

John Grounds, a spokesman for the charity, said: "Action Research and other awareness campaigns have made significant progress in the fight against these serious birth defects.

"It would be disastrous to see these efforts undermined, and for women to stop taking the recommended dose."