Pregnancy and lactation in relation to range of acceptable carbohydrate and fat intake

The additional energy requirements of pregnancy are needed for increases in maternal (breast, uterus and adipose) and fete-placental tissue accrued du ring pregnancy as well as the additional running cost of pregnancy for exam ple increased cardiac output. Based on prospective longitudinal studies, th e additional energy requirements of pregnancy range from >500 MJ in Swedish women to net savings of approximately 50 MJ in women in The Gambia with th eir usual nutritional intake. In addition to the wide variation in estimate d energy expenditure among various ethnic populations, there is as much as a 10-20 fold range in the total energy cost of pregnancy and lactation with in relatively homogenous populations. The estimates of energy intake in these studies, however, are generally les s than the estimates of total energy expenditure. The discrepancy between e nergy intake and energy expenditure during pregnancy is most probably due t o several factors including decreased maternal activity, unreliable reporti ng of energy intake and possibly increased metabolic efficiency of basal me tabolic rate, thermic effect of foods and physical activity. Based on recent studies, variations in maternal pregravid glucose insulin s ensitivity may account for part of the observed variability associated with maternal metabolic adaptations during pregnancy. Decreases in insulin sens itivity have a significant inverse correlation with accretion of adipose ti ssue in early pregnancy. Likewise, there is a significant inverse correlati on between decreases in basal oxygen consumption with increases in endogeno us glucose production. The mechanism for these changes remain speculative. Additionally, although serum leptin concentrations increase 66% in early pr egnancy and are correlated with maternal fat mass and basal energy expendit ure, the increases in serum leptin occur prior to any significant increases in body far or basal metabolic rate suggesting that pregnancy represents a nother leptin resistant state. Based on these data, specific recommendations for acceptable carbohydrate a nd fat intake during pregnancy and lactation are nor possible for every wom an at this time. Additional prospective studies, evaluating long-term mater nal and neonatal outcome are needed before more meaningful nutritional reco mmendations can be proposed.