Cot death rates in England and Wales are going down. In Avon, which used to report one of the highest levels of sudden infant death syndrome (SIDS) in the country, there have been no unexplained deaths of babies under a year since March 1992.
Dr Peter Fleming, whose research at Bristol's Institute of Child Health inspired the government's Back to Sleep campaign in which parents were advised not to place sleeping infants in the prone (face down) position says he expects the new advice to halve the cot death rate nationwide.But is the simple expedient of lying a baby on its back sufficient to guard against sudden death? The government's campaign also advises against parental smoking and overheating of the baby, two factors known to increase the risk.
Meanwhile, the extraordinary work of Barry Richardson, a materials deterioration scientist, could offer an explanation for the rise in cot death during the 1980s. His theory that the biodeterioration of cot mattresses is a primary cause of SIDS may be controversial but it has not been refuted.
"All cot mattresses become naturally infected by an otherwise harmless domestic fungus Scopulariopsis berevicaulis, particularly in the area affected by warmth and perspiration," he says.
"After several months the organism becomes sufficiently active to convert any phosphorous, arsenic or antimony compounds in the mattress materials into toxic gases" .
Richardson notices that first born infants, "particularly those in higher economic classes", are least at risk from SIDS, and he suggests that such babies are most likely to be sleeping on new mattresses, in which fungal infection is not yet rife.
Even the overheating theory fits with Richardson's findings: "Overwrapping in response to cold weather traps the gases, but also causes overheating, which increases the rate of gas generation."
Other researchers have been concerning themselves with the implications of the cot itself. Professor D P Davies at the Department of Child Health at the University of Wales, Cardiff, compared the incidence of SIDS among local Bangladeshi and Welsh families.
Despite poorer socioeconomic conditions, crowded and unheated housing, younger mothers and more siblings, the Bangladeshi families (along with other Asian groups) suffer a low incidence of SIDS approximately half that of the white majority (BMJ, 2 January 1993).
"Bangladeshi infants are constantly in a busy social and tactile environment," says the report, "whereas Welsh babies grow up in smaller households in which independence is encouraged."
The study concluded: "Long periods of lone quiet sleep may be one factor that contributes to a higher rate of sudden deaths in white than in Asian infants."
As I have been saying this myself for some years, I was particularly interested to see the cautious response from the Foundation for the Study of Infant Death to the Cardiff research. It warned that other research has identified babies sleeping in the same bed as adults as a risk factor.
The "other research" which identifies co-sleeping as a risk factor is based on a study of the Maori population which suffers a cot death rate of four per 1,000 live births, the highest SIDS rate in the world.
Active birth pioneer Dr Michel Odent, who has conducted his own (unpublished) research into co-sleeping and cot death, immediately pointed out that there were unusual factors which made the Maori population an untypical group. Alcoholism is prevalent , and the group as a whole has a history of bronchial problems.
The New Zealand researchers themselves came back with a clear statement on the Maori study. Sleeping with your baby does not increase the risk of SIDS for your baby, since, as they point out, "bed sharing was a risk only in the Maori population." (BMJ, 2 January 1993).
In fact, it is the mothers' smoking (plus other factors including the poverty of families and lack of breastfeeding) which are most likely to endanger the life of the vulnerable baby.
Another suspicious area which has not been investigated is the work by Archie Kalokerinos attributing a larger percentage of the SIDS deaths among poorly nourished Australian aboriginal children to the whooping cough vaccination.
Is there a moral in all this? Firstly, it seems clear that the most useful research tends to dovetail. Toxic gases emanating from a cot mattress would make SIDS eight times more likely for a baby lying on his tummy, says Barry Richardson.
Smoking was "very rare" among Bangladeshi mothers in the Cardiff study. One study from Birmingham found that 22 per cent of Asian babies were put to sleep on their backs, 98 per cent slept in the same room as their parents for at least a year, 34 per cent in the same bed.
While we congratulate researchers from Bristol on the immediate impact of the Back to Sleep campaign, perhaps we should remind ourselves that a baby who sleeps with, and feeds from, his mother at night, will usually lie on his back or side.
Once again, science may be catching up with three million years of human evolution.