Nutrition during pregnancy: an evaluation of maternal dietary intake and the development of foetal adiposity

Research Doctorate - Doctor of Philosophy (PhD)Early life environmental factors, including maternal dietary intake and nutritional status during pregnancy, can program offspring health outcomes in later life. Given the rapid worldwide burden of non-communicable conditions (e.g. obesity, type 2 Diabetes Mellitus (T2DM) and cardiovascular disease), early prevention by optimising maternal, foetal and infant nutrition has been identified as a strategy that is likely to be beneficial and cost effective. The primary purpose of this thesis is to evaluate the dietary intakes of women during pregnancy, and to investigate the relationship between maternal intake and foetal body composition. Three research studies were undertaken to meet these aims. A systematic review of the available literature determined the energy, macronutrient and micronutrient intakes of pregnant women in developed countries, and appraised the nutritional adequacy of intakes compared to current recommendations. Meta-analyses provided evidence that the dietary intakes of pregnant women do not match with international recommendations. Energy and carbohydrate intakes were generally below recommendations, total fat and saturated fat intakes were generally above recommendations, while protein intakes were within the recommendations. Secondly, pregnant women reported suboptimal micronutrient intakes with folate, iron and vitamin D intakes consistently below nutrient recommendations in all geographical regions. A cross-sectional study evaluated the dietary intakes of Australian women of reproductive age by pregnancy status, in comparison to national food group recommendations. This determined whether their eating patterns achieved the recommended intakes of nutrients important for pregnancy. Data were obtained from the Australian Longitudinal Study on Women‟s Health (ALSWH), young cohort aged 25 – 30 years in 2003 (n 9076). Pregnancy status was self-reported as pregnant (n 606), trying to conceive (n 454), given birth in the last 12 months (n 829) or other (n 5597). Diet was assessed using a validated 74-item food frequency questionnaire (FFQ). Daily food group servings and nutrient intakes were compared to the Australian Guide to Healthy Eating (AGHE) and Australian Nutrient Reference Values (NRVs). The study found that the AGHE does not enable pregnant women to meet all the NRVs and further the contemporary eating pattern of Australian women that do achieve nutrient intake targets does not align with the AGHE recommendations for daily servings of food groups. Longitudinal data, collected prospectively as part of the Women and Their Children‟s Health (WATCH) study from a cohort of 179 pregnant women, was used to evaluate whether maternal macronutrient intakes are associated with foetal body composition and secondly, whether the macronutrient content of maternal diet is associated with the adequacy of micronutrient intakes, compared to Australian dietary recommendations. Linear mixed-model regression analyses and parametric response surfaces provided evidence that there may be a target maternal macronutrient profile associated with optimal foetal body composition. The development of foetal abdominal visceral area throughout gestation was positively associated with higher maternal protein intakes, decreased starch intakes and a higher protein to carbohydrate (P:C) ratio. Foetal midthigh lean area was positively associated with increased maternal PUFA intakes and decreased SFA intakes. Response surfaces for micronutrient intakes were optimized when the percentage energy was within intermediate protein (18-20%E), intermediate fat (28-30%E) and intermediate carbohydrate (50-54%E) intakes. Results suggest a moderate protein intake may support pregnant women to consume the largest variety of nutrients across all food groups. In conclusion, the study findings presented in this thesis provide evidence that dietary intakes during pregnancy commonly fail to achieve target NRVs and that current dietary selection models to guide the food consumption of pregnant women in Australia may require revision. Findings also suggest that foetal body composition and maternal micronutrient adequacy may be modifiable by nutritional interventions in the mother, with a particular emphasis on protein as a key driver of these relationships. These results are likely to have important implications for the offspring‟s risk of non-communicable disease, and key recommendations for future research to support optimal health outcomes are provided