WOMEN WITH low levels of a common B vitamin in early pregnancy have a significantly increased risk of delivering a child with spina bifida, a new study has found. It showed that women with the lowest levels of B12 were almost five times more likely to deliver a child with this and related conditions.
The new findings on what collectively are known as “neural tube defects” were published yesterday in the journal Pediatrics. The findings are particularly important for Irish women, given Ireland has the second highest incidence of neural tube defects in the world.
Conditions such as spina bifida and anencephaly affect about one in 1,000 pregnancies here, with about 75 new cases each year.
The neural tube begins to form early in the growing foetus and protects the developing spinal cord. It begins to form just three to four weeks after conception and finally closes completely in the 26th or 27th week.
These disorders occur when the tube fails to close properly, something which leads to varying degrees of disability and, in the worst case, to death.
The research team including Dr Anne Molloy and Prof John Scott of Trinity College and Dr Peadar Kirke of the Health Research Board analysed B12 levels in blood samples collected during early pregnancy from three groups of Irish women between 1983 and 1990.
They found these defects were between 2.5 and almost five times more likely in women with low levels of B12. They were also able to show that these risks were separate to the known dangers of having low levels of another nutrient, folic acid, in the first stages of pregnancy, risks that have been recognised since the early 1990s.
Strict vegetarians could be particularly at risk, the authors suggest, given that the richest sources of vitamin B12 were meat and animal-based foods.
These results “suggest that the two vitamins are jointly involved in influencing a woman’s risk”, stated lead author Dr Molloy.
Taking folic acid supplements before pregnancy did not prevent all neural tube defects, indicating other factors were also involved, Prof Scott said. “Our study suggests that women can reduce their risk further by ensuring that they have adequate B12 levels before they become pregnant.”
The study involved researchers from Trinity College Dublin, the Health Research Board and the US National Institutes of Health (NIH). The Health Research Board and the US NIH co-funded the important new study.
Spina Bifida Hydrocephalus Ireland welcomed the findings but urged caution in their interpretation. “I would like a bit more proof,” stated the group’s chief executive officer, George Kennedy.
“If that is proven that would be brilliant news,” he said. He cautioned however against self- medication with supplements until more evidence was available from follow-up studies.
This could be the first clear evidence that B12 had a role to play in neural tube defects, said Helene McNulty, professor of nutritional science in the University of Ulster’s biomedical sciences research institute.
She has conducted extensive research into how low levels of folic acid could increase the risk of these disorders. Folic acid and B12 were related substances in the body and so the findings were “certainly very believable”, she said. “It is entirely consistent with what we know about folic acid that B12 could have a role,” she added.