Experts have many theories about infant deaths. But are they any closer to finding a cause?

A stomach infection, might, it's suggested, be a cause of cot death. The new research, reported in the Archives of Diseases in Childhood, suggests a link between the stomach bug Helicobacter and Sudden Infant Death Syndrome (SIDS).

A stomach infection, might, it's suggested, be a cause of cot death. The new research, reported in the Archives of Diseases in Childhood, suggests a link between the stomach bug Helicobacter and Sudden Infant Death Syndrome (SIDS).

The researchers at Manchester Royal Infirmary found that children whose death was put down to SIDS had a higher level of the bug, which could have been transferred from the mother by saliva, triggering a cascade of events and symptoms that might result in the baby's death.

The researchers found the bug and SIDS have other things in common. "Both are more common in poor communities, to single-parent families, in males, and in overcrowded living conditions,'' says the report.

On the other hand, something completely different may be responsible for each, some, or all of the 400 or so deaths in Britain each year that are put down to SIDS.

For new mothers and fathers, the latest research on the stomach bug Helicobacter pylori adds to what has become a huge list of suspects and things to avoid. Plastic mattresses, toxic fumes, thick duvets, a low birth weight, twins, heart defects, stomach bugs, warm clothing, secondary smoking, drinking, sharing beds (or not sharing beds, depending which research you read), careless carers, and having too many babies too quickly, have all been named at one time or another as culprits.

Little wonder that many parents have difficulty in navigating their way around the likely, the unlikely and the downright impossible. For some parents, the fears and forebodings raised by research may blight their early months with the newborn baby. "I think I nearly froze Patrick to death in those first few months, I was so anxious about overheating him," says one new mother. "He certainly began to sleep better when I dared to add an extra blanket."

For parents whose child's death is put down to SIDS, each new piece of research may also give rise to feelings of guilt. Who can imagine the soul searching that must have been triggered by the results of the research, since found wanting, that found that toxic fumes from cot mattresses were to blame for cot deaths?

SIDS is defined as the sudden death of an infant or young child which is unexpected by the medical history, and in which a thorough post-mortem examination fails to show an adequate cause of death. Although it is often seen as a cause of death, it is not so much a diagnosis as a lack of one. A child does not die of SIDS: he or she dies of something that cannot, at present, be explained.

All illnesses and diseases involving children arouse emotions, but SIDS is in a category of it is own, largely because of its unknown causes, the previous good health of the child, and the fact that it strikes so quickly with no warning.

"It is not just neurotic mothers who don't know what to do. I'm afraid it may well be confusing for lots of mothers,'' says Joyce Epstein, director of the Foundation for the Study of Infant Deaths (FSID) "I wish a little more care and attention was devoted to what is published and what isn't. Parents never expect to outlive their child and if a child dies from unidentified causes, there is inevitably a feeling of 'What did I do wrong?' It is unavoidable, and parents are vulnerable to every new report that comes out. Of course, research has to go on, but it is a pity that researchers sometimes publish at the hypothetical stage, which then gets wider publicity in the media. What they say may sound scary to parents, but they don't know what it means.

"Toxic fumes and mattresses is a perfect example. At the time, we were always trying to say there was no evidence, but the media kept on about killer mattresses because it made a good story. But it never had any basis in fact. At FSID, we look at all the research and we don't put anything out unless it is backed by evidence.''

The numbers of cot deaths has been falling for a number of years. In 1969, there were 1,200 sudden infant deaths in England and Wales, but during the 1970s and 1980s, that had fallen to 1,000 a year. By the start of the 1990s, that figure had halved, thanks largely to the Back to Sleep campaign, which encouraged parents to place babies on their backs rather than their stomachs. Latest figures show about 419 deaths a year.

The Back to Sleep campaign may have resulted in a big drop in deaths, but no one knows why for sure. "We found through epidemiology research that babies who sleep on their backs are more likely to survive than babies who sleep on their fronts, but we still have no idea why. What has always been the case is that SIDS is multifactorial. There are likely to be a number of things happening to babies at a vulnerable stage in their development,'' says Epstein.

That suggests it is unlikely there will ever be one answer to SIDS, and that the cause of death may be different in each case.

FSID 24-hour helpline: 020-7233 2090