The studies of PERILIP are conveniently divided into 10 workpackages or into 5 themes. Inevitably, there are a number of questions which are addressed by more than one of these study areas or thematic areas. Below we present the questions and the conclusions drawn from the new PERILIP studies.

The combined observations confirm that IUGR is associated with reduced placental development and function. Reduced transfer of some essential fatty acids, increased oxidative stress and low concentrations of important pregnancy hormones all contribute to impaired foetal growth. Animal studies have suggested some long-term implications of low birth weight on the glucose-insulin axis.

The combined results from several studies suggest that fish oil supplementation can have beneficial results for the development of the placenta and for the development of the foetus and newborn. Furthermore, the physiology of the pregnant or lactating female seems to be adapted to make best use of available long-chain n-3 fatty acids. Nevertheless, caution is required because there is evidence that too much n-3 fatty acid may disrupt the balance with n-6 fatty acids or put extra stress on anti-oxidation mechanisms (see below) and could have detrimental effects.

With respect to the lipid content of the diet at least, it is clearly important that the optimum content and composition is available from the very beginning of pregnancy. This would appear to be particularly important for brain development. During the anabolic phase (roughly the first half) of gestation, adipose tissue provides a store of the essential fatty acids which can be made available during the catabolic phase (second half) of gestation, particularly at times of dietary restriction, and at the onset of lactation. For these reasons, the prior dietary history of the mother is probably also important, suggesting that potential mothers should start thinking about their dietary requirements some time before beginning their families.

The experiments with pigs showed clear benefits of supplementing the diets of pregnant sows with 10% extra energy either in the form of particular lipids or of extra carbohydrate. The benefits were seen in terms of the health and viability of the offspring and in the condition of the mother. It is not clear whether these results are transferable to humans especially in Western Europe where dietary restriction (unlike the situation with commercial pigs) is rare, except possibly for psycho-social reasons. The recommendation of our expert panel was that “dietary fat intake during pregnancy and lactation (as a proportion of energy intake) should be the same as that recommended for the general population.”; it made no recommendations about the total energy intake but it is accepted that it should be increased as pregnancy progresses. There were no clear differences between the energy intakes of women with IUGR pregnancies compared to (normal) AGA pregnancies.

n-3 PUFA when present in excess are more susceptible to oxidation than n-6 PUFA and result in greater utilisation (seen as lower concentrations) of anti-oxidant vitamins.

It is possible to manipulate the fatty acid composition of milk by altering the fatty acid composition of the maternal diet but small supplements are unlikely to have much effect. As mentioned above, changes in early pregnancy (and earlier) are likely to be the most effective. Because of interactions between the biosynthetic pathways leading to LC-PUFA, the effects are more complex than first imagined and steps to ensure an adequate supply of arachidonic acid (AA; derived from dietary precursors) are advised.

Great care has to be taken before it is possible to extrapolate results from model systems to living humans, especially when there are clear differences in their anatomy or physiology (as with the placental structure of pigs, for example). Nevertheless, careful use of these systems can yield (and has yielded) results and lead to conclusions that would not otherwise have been possible.