Sudden infant death syndrome (SIDS) may be caused by the mother's lack of iodine, a Canadian professor has hypothesized. This lack, which may be exacerbated by excesses or deficiencies of selenium, could also be the cause of respiratory distress synd

Prof Harold Foster, from the University of Victoria, points out that SIDS and RDS have a number of common factors, and occur most commonly in male babies with low birth weight, in babies from multiple births, while the mother tends to be very young and from a poor background. Such a child who has survived RDS has a very increased risk of deaths from SIDS, he adds. Iodine deficiency in the mother could result in maternal goiter, accompanied by depressed fetal blood levels thyroxine (T4) or triidothyronine (T3), levels of which can be depressed by a lack of selenium. "It would not be surprising if fetal and infant blood levels T4 and/or T3 deficiencies were responsible for the subtle neurological, cardiorespiratory and metabolic developmental deficits seen in SIDS autopsies," says Prof Foster.

He points out that the level of SIDS deaths is at its highest in the Indian reservation of King County, Washington, with a rate of eight per 1,000 births, and in Canterbury, New Zealand, where the SIDS mortality rate is 7.9 per 1,000 births. Both locations are iodine and selenium deficient. Conversely, the lowest rates are recorded in Stockholm, Sweden; urine samples have shown that Stockholm children have the highest levels of iodine of infants tested from 14 European cities (Townsend Letter for Doctors, December, 1995).

l Toxic gases released from contaminated polyvinyl chloride (PVC) mattress covers do not cause SIDS, new research has established. The theory was suggested by analytical chemist Barry Richardson, and was taken up in a Roger Cook television programme in 1994 in Britain.

Richardson claimed that fire retardants, such as antimony, on the mattresses could release toxic fumes if they reacted to moulds and other substances. But a trial launched to investigate his claims did not find sufficient evidence to support his theory (The Lancet, December 9, 1995).