快猫短视频

PREGNANT women who take the recommended folic acid supplements may be more
likely to have twins, say researchers in Sweden. The supplements cut the risk of
birth defects, but twins have their own problems鈥攖hey are more likely to
be premature, have low birth weights and suffer from cerebral palsy.

Many women take the vitamin folic acid before and during pregnancy to reduce
the risk that their babies will have neural-tube defects, such as spina bifida.
In the US, the compulsory addition of folic acid to breakfast cereals and
wholemeal bread since 1998 has reduced the incidence of spina bifida by 19 per cent
(快猫短视频, 30 June, p 17).
This has increased pressure on other nations to follow suit.

But the costs could outweigh the benefits, especially in countries where
spina bifida is relatively uncommon, according to Bengt K盲ll茅n of
the Tornblad Institute in Lund. He and his team have looked at records from the
Swedish Medical Birth Registry, which has gathered data on the use of medicines
by pregnant women since 1994.

According to the records, 2569 women said they used folic acid supplements.
The rate of twin births for these women was 2.8 per cent. In the general Swedish
population, however, 1.5 per cent of births in the late 1990s were twins.

The reasons for the difference are not clear. K盲ll茅n鈥檚 team tried
to allow for other factors鈥攐lder mothers and those using IVF, for
instance, who are already more likely to have twins. It鈥檚 possible that folic
acid somehow increases the probability of multiple ovulation or implantation of
more than one egg.

If folic acid does increase the number of twins, the supplements could cause
more problems than they solve. K盲ll茅n calculates that if 30 per cent
of 100,000 women in Sweden took folic acid supplements, there would be 225 extra
pairs of twins. These 450 babies would often be premature, have low birth weight
and an increased risk of cerebral palsy. At most, only 4 or 5 spina bifida cases
would be avoided.

K盲ll茅n says more research is needed to pin down the effects of
folic acid tablets. 鈥淚 think one should consider the pros and
cons鈥攅specially in areas like Sweden with a low rate of spina bifida,鈥� he
says.

The British government is considering making it compulsory to add folic acid
to flour. Two years ago the committee appointed to explore this suggestion
concluded that adding 240 micrograms of folic acid to every 100 grams of flour
could cut the numbers of babies born with neural-tube defects by 41 per
cent.

John Grimley Evans of Oxford University, who chaired the committee, says it鈥檚
important that any risks that might result from extra folic acid should be
identified. 鈥淭he more of these possible things we identify so that people can
monitor them, the better,鈥� he says. He has informed the Department of Health of
the Swedish report.

However, he stresses that more work needs to be done to establish whether the
link is genuine. Even if it is, he adds, it might mean one or both fetuses in
twin conceptions are spontaneously aborting in women who don鈥檛 take enough folic
acid: 鈥淚s that a good basis for public policy?鈥�

Nicholas Wald, an expert on preventive medicine at St Bartholomew鈥檚 Hospital
in London, is not convinced by the Swedish research. He would like to see a much
larger study looking only at younger women who all have a similar expected rate
of twins and are unlikely to have had fertility treatment.