Optimal foetal growth in the reduction of learning and behaviour disorder and prevention of sudden infant death (SIDS) after the first month.

A theory is presented that a diet low in polyunsaturated fatty acids (PUFA) in the third trimester of pregnancy may delay myelination and brain maturation. This may underpin learning and behaviour disorders and sudden infant death (SIDS) after the first month, conditions that are associated with lower than average birthweight. Epidemiological evidence is reviewed showing an inverse relation between the proportion of heavy newborns (> 3500 g) and infant mortality rate. Some countries with a lower proportion of heavy newborns despite equally high standards of living and medical care have higher post-neonatal death rates. The higher rates are solely due to SIDS which has a peak mortality within 80-100 days. It is hypothesised that as this is a time when myelination peaks, SIDS may be due to maturational delay. Evidence of subtle CNS changes in brainstem structures and in the neuromuscular system supports an instability in brainstem control systems. Moderate iatrogenic dietary restriction predominates today, but a rising number of women favour a low-caloric low-fat diet especially in the third trimester when the foetus is most susceptible. This may lead to a depressed birthweight, delayed somatic growth and neuronal maturation, such as is observed in SIDS victims. The majority exposed to suboptimal conditions survive, but a few suffer SIDS; confirming post-neonatal susceptibility. Many, especially males, present minor CNS signs and learning/behaviour disorders that could be the sequelae of repeated hypoxic episodes, such as recorded in more than 80% of SIDS victims. To reduce learning/behaviour disorders and prevent death from SIDS after the first month, it is necessary to ensure optimal development by promoting foetal growth. It is advised to avoid unnecessary dieting and to favour a diet high in PUFAs, thus prolonging pregnancy and so increasing birthweight.