Irene Cetin, Professor of Obstetrics and Gynecology, Hospital Luigi Sacco, University of Milan, Italy
“Maternal body mass index (BMI) and gestational weight gain (GWG) represent the major determinants of energetic adaptation and incremental energy needs during pregnancy. Both high and low GWG have been associated with adverse pregnancy outcomes even in women with a normal pre-pregnancy BMI. GWG of obese pregnant women frequently exceeds the recommended ranges, due to an imbalanced diet and lack of daily physical activity. Malnutrition, resulting from imbalances of macro- and micronutrients before and during pregnancy, can negatively affect both mother and fetus, also resulting in low birth weight (LBW) and/or intrauterine growth restriction (IUGR). Maternal im- proper diet may affect fetal growth both directly by altering placental nutrient availability, and indirectly by affecting the fetal endocrine system and by epigenetic gene expression modulation. Study results show that most pregnant women do not follow an appropriate diet in pregnancy and that their intake of micronutrients is inadequate, particularly for iron, omega-3 fatty acids and folate as well as calcium and vitamin D.
Each stage of fetal development is dependent on and influenced by appropriate maternal nutrient supply; nutritional insults program postnatal pathophysiology, with the timing of the insult impacting on the nature of adult diseases. The period from conception to implantation is particularly important for fetal growth and development. Recent studies strengthened the association between specific dietary lacks and adverse neonatal outcomes. In particular, higher-birth-weight babies, with reduced risk of preterm delivery and preeclampsia, have been linked with high calcium intake during pregnancy, which is now recommended for pregnant and lactating women (1). A recent study showed a significant reduction of small-for-gestational-age (SGA) births in multivitamin users, with the strongest association for regular use during a 12-week pericon- ceptional period (2). Current investigations focus on fetal fat mass growth in relation to a number of mater- nal nutritional factors, from maternal obesity to micronutrient intake.
Macro- and micronutrients in the maternal diet directly regulate DNA stability and phenotypic adaptation by influencing the availability of methyl donors and mechanisms promoting DNA stability. Interestingly, meta-bolism of amino acids (glycine, histidine, methionine, and serine) and vitamins (B6, B12, and folate) plays a key role in providing methyl donors for DNA and protein methylation, underlining the importance of nutrient imbalance in these processes. Placental growth impairment may also result from changes in energy utili- zation; particularly we have shown that mitochondrial DNA content, accounting for the number of mitochon- dria in the cell, is altered in human IUGR placentas and maternal blood. This may indeed lead to changes in placental oxygenation and therefore contribute to the chronic hypoxia that is a major feature of IUGR. Mitochondria are regulated by a number of factors, among which calorie restriction and iron may play an important role. Moreover, iron levels are decreased in small-for-gestational-age babies, and we have pre- viously shown that iron placental transporters are significantly reduced in IUGR pregnancies. We aim to study the potential link between iron, mitochondrial function and placental respiration.
The mix of nutrients that finally reaches the fetus through the umbilical circulation is the result of maternal diet and metabolism and of placental circulation as well as exchange properties. Moreover, nutrient utilization by the placenta itself is substantial. Major nutrients that need to be provided are glucose, amino acids, and lipids. They require specific transporters located on the terminal villi. Reductions in placental transport of amino acids have been specifically associated with intrauterine growth restriction. However, micronutrients are also needed by the fetus, although very little is known about the potential effects of their deficiency. Maternal anemia (e.g. due to iron deficiency) has been associated with increased risk of neurological dis- orders in the offspring. Iron deficiency represents the most frequent nutritional insufficiency worldwide. Iron deficiency and the consequent iron deficiency anemia are encountered with a high prevalence in women of fertile age generally, as well as in pregnant and postpartum women. Iron needs increase significantly, by 100%, during pregnancy. The absorbed iron is used to expand the maternal erythrocyte mass, to fulfill fetal and placental iron needs, and to compensate for iron loss at delivery, e.g. blood loss. Iron deficiency represents a terrible problem in developing countries, but is also very common in developed countries.”
Based on: Cetin I. Maternal nutrition in pregnancy: role in fetal development. Presentation at The Power of Programming 2014 – EarlyNutrition Conference in Munich, Germany. March 2014.