Resumen de Calidad de la dieta durante el embarazo y su relación con el crecimiento fetal
Background and objectives Foetal growth restriction is an important determinant of infant mortality and morbidity in the short and long term. The pre-conceptional nutritional status and the intake of certain nutrients or food groups during pregnancy have been associated with foetal growth; however, in high- income countries, where the population is assumed to have an adequate nutritional status, this association has not been clearly established. The study of individual dietary factors is a useful and valid approach, however, it does not take into account the interactions between nutrients, and therefore, may not reflect the actual global effect of dietary intake. As an alternative, there has been growing interest in assessing diet as a composite measure and its effect on health outcomes by using diet quality indices, however, their use in pregnant populations has been scarce.
Recent evidence suggests that women from high-income countries have inadequate dietary intakes during pregnancy, which if confirmed in our setting, could imply that improvement in specific dietary factors or the overall quality of diet, could potentially lead to benefits in foetal development. The aim of this thesis is to evaluate dietary intake and supplementation during pregnancy, diet quality, and its relationship to foetal growth in a population of pregnant women living in a Mediterranean area.
Methods We used data from 822 pregnant women and 787 infants belonging to the INMA-Valencia cohort. Pregnant women were recruited between February 2004 and June 2005 during weeks 10-13 of pregnancy and were interviewed with specific questionnaires, which collected information on socio-demographic and life-style variables. Dietary intake data was obtained through a validated food frequency questionnaire. Information on maternal anthropometry and newborn variables was obtained from medical records. A customized model based on parental socio-demographic and anthropometric characteristics in order to define foetal growth restriction in weight, height, and head circumference was used. A descriptive analysis of dietary intake during the first trimester of pregnancy was performed regarding food groups, macro and micronutrients. Adequacy was estimated according to current recommendations and considering both, food and dietary supplements intake. In addition, we explored the differences according to selected socio-demographic characteristics. To examine the effect of diet quality during pregnancy on foetal growth, we used the Alternate Healthy Eating Index (AHEI), adapting such index to pregnancy. This relationship was analysed using multivariate models. Furthermore, we conducted a descriptive review of evidence in relation to the intake or status of iron ¿which deficit is the more extended worldwide- during pregnancy, and its effect on foetal growth.
Results Over 50% of pregnant women did not meet the recommendations for the consumption of cereals and pulses, carbohydrates and n-3 and n-6 fatty acids while exceeded the reference values for total fat intake. Between 99% and 68% of the population did not reach established recommendations for folate, iron and vitamin E intake through diet. Supplement use significantly improved the appropriateness in the case of folic acid but not in that of iron; however, it also lead to overpassing limits of intake considered safe. Vegetable consumption was positively associated with age. Younger and less educated women consumed less protein and n-3 fatty acids and higher quantities of trans fatty acids, and micronutrient intake was less adequate. Spanish women showed a lower intake of fruits and carbohydrates and higher intakes of protein, and fat, compared with foreign women.
Regarding the relationship between maternal diet quality -assessed by AHEI- and foetal growth, we observed a positive association between diet quality and adjusted weight and height at birth. Overall, the adjusted weight and height of the delivered babies increased as the quality of the maternal diet improved (measured by AHEI categories), p for trend 0.009 for weight and 0.013 for height. Newborns of women classified in the fourth quintile were 126.3 g heavier and 0.47 cm longer on average, than those of women in the lowest quintile. Mothers with the highest diet quality were less likely to have a baby with foetal growth restriction in weight, compared with those with the worst diet (OR 0.24, CI: 0.10, 0.55). A non-significant trend was observed in the case of foetal growth restriction in length and head circumference.
Concerning the effect of iron on foetal growth, the literature reviewed suggest that iron deficiency at different times during pregnancy, including early pregnancy, has an adverse effect on foetal growth. Regarding iron supplementation, it is suggested that it has a beneficial effect, although quality of evidence is weak.
Conclusions Women in the area of study had an inadequate intake of several nutrients which are important during pregnancy. Age, education and country of origin are factors significantly related to food intake and dietary adequacy.
A high-quality diet in the first trimester of pregnancy is associated with increased anthropometric measures at birth and a reduction in the risk of foetal growth restriction, especially in weight.
Even in early pregnancy, iron deficiency is related to impaired foetal growth and supplementation seems to be beneficial; nevertheless, high quality research contributing to update recommendations on doses and timing of supplementation is needed.
