NEW YORK (Reuters Health) – The number of newborns in Europe affected by heart defects appears to have fallen in recent years, but it’s not clear why, says a new study.

A team of European Union researchers analyzing millions of birth records found that the number of European babies born with heart defects fell from around seven in every thousand births in 2004 to around six per thousand by 2007- a drop of around four percent each year.

While any drop in the numbers of babies born with birth defects is good news, experts noted that the decline is a modest one and the researchers can only speculate about the reasons for it.

There is cause “for a high level of skepticism,” said Dr. Joe Simpson at the New York-based March of Dimes foundation, a non-profit organization that works to improve babies’ health.

“It would be lovely if… true,” Simpson told Reuters Health, but given the lack of explanation for the change, “whether it persists over time remains unclear.”

For the new study, a team led by Dr. Babak Khoshnood at the National Institute for Health and Medical Research (INSERM), in Paris, France, looked at data on congenital heart defects collected in 16 mostly western-European countries between 1990 and 2007.

They found 47,000 cases of congenital heart disease among more than seven million births.

According to the report, published in the Journal of Pediatrics, cases of the most severe forms of CHD – including conditions like hypoplastic left heart syndrome, when the left side of the heart doesn’t develop properly – has held steady at around five per 10,000 births since 1990.

But less severe conditions, like ‘hole in the heart’ syndrome, decreased from around 50 to 40 cases per 10 000 births, between 2004 and 2007. For a country like France, with around 780,000 births a year, that means about 780 fewer babies born with heart problems every year.

Khoshnood speculates that increased folic acid intake by European women is a possible cause of the decline in defects. But, “we don’t have the data to know for sure,” he added.

A recent study in Quebec, Canada, found that the number of babies born with heart defects dropped after 1998, shortly after the government began adding folic acid to staple foods like cereal and bread.

Folic acid fortification programs were introduced in both Canada and the U.S. in 1998 to reduce the number of serious birth defects in the spine and brain, known as neural tube defects. But there are no such programs in Europe.

It’s possible that European women have increased their consumption of folic acid and are starting to follow recommendations to take it before and during pregnancy, Khoshnood said.

“People are realizing that there is a lot of voluntary fortification. In some breakfast cereals and so on, there is folic acid added, although it’s not mandatory. Women are getting folic acid even if they don’t take any.”

Dr. Sunil Malhotra, a surgeon specializing in congenital defects at New York University, points out, however, “Folic acid has been a part of prenatal care in the U.S. for the better part of a decade, but there hasn’t been a similar decrease (in heart defects) here.”

According to the American Heart Association, the causes of congenital heart defects are still unknown. So researchers can only speculate about what could be causing the European decline.

Simpson and Malhotra noted further limits to the new study

Methods to diagnose birth defects have changed during the last 20 years, said Simpson. And with babies leaving the hospital within a day of being born, there is less time to spot heart defects.

Some conditions, including hole in the heart syndrome, don’t show up until a couple of days after birth, he said.

“I was not overwhelmed by the strength of the data,” Malhotra added. The study draws on data from a lot of different country registries that each collect and store data in a different way, and that data can often be incomplete, he explained.

According to the Centers for Disease Control and Prevention, 40,000 babies are born with heart defects in the U.S. every year. Close to one million adults in the U.S. live with congenital heart disorders, which can cause tiredness, shortness of breath and abnormal heart rhythms.

Advances in surgical techniques mean it’s now possible to treat many heart defects, although life-long follow-up care is still essential. Mild cases can often be treated with medication.

“One thing we do know,” Malhotra said, is that detection of CHD in the womb has “improved markedly, as has care for mothers with babies with CHD.” As a result, those mothers can get more prenatal attention and “have better outcomes when those babies deliver.”

SOURCE: bit.ly/N0bJuX Journal of Pediatrics, online 26 July, 2012.