Since the 1960s the structural requirements for the growth, development and function of the brain have become better understood due to the recognition of the prodigious energy needs for brain development and its structural requirements for lipids. The most vulnerable period of neural development is during embryonic and fetal growth. There is now both retrospective and prospective evidence that maternal nutrition prior to conception is most important to pregnancy outcome. Our studies on maternal nutrition in pregnancy again illustrate the relationship of maternal nutrition to birthweight and head circumference. In a study of 513 pregnancies we found that nutrient intakes in mothers of low birthweight babies were well below those of mothers whose babies were in the 3.5-4.5 Kg range at which morbidity is at its lowest. Nutrient intakes tracked with birthweight, independent of smoking and alcohol up to, but not above 3,270 g. The closest correlations were obtained with the diet of the mother at or about the time of conception rather than later in the pregnancy. Our studies also reveal that premature and intrauterine growth retarded babies were born with deficits of the types of essential fatty acids (arachidonic AA, docosahexaenoic DHA acids) known to be required for brain development. Deficits of brain DHA have been found experimentally to impair visual and cognitive development and also to cause haemorrhage, not unlike peri-ventricular haemorrhage in low birthweight babies, the above evidence is suggestive of a route to test the prevention and treatment of these types of membrane related disorders.