Fetal development depends on a proper supply of nutrients, including micronutrients in the mother’s bloodstream. Maternal nutrition has a direct impact on their child’s health during adulthood, which may be a major factor in the global epidemics of obesity and NCDs.
Furthermore, there are direct relations between low birth weight and susceptibility to a number of diseases in later life, including insulin-related metabolic disorders, type II diabetes, central adiposity, abnormal lipid metabolism, obesity, arterial hypertension, cardiovascular diseases, fatal ischaemic diseases and renal disorders.
BMI is evaluated according to the classification adopted by WHO in 1995:
- BMI < 18.5 kg/m’: underweight;
- BMI 18.5-24.9 kg/m”: normal;
- BMI 25-29.9 g/m’: overweight; and
- BMI >30 kg/m’: obese.
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Obesity before and after conception increases the risks for a range of complications in pregnancy. Being overweight or obese before conception increases the risks for arterial hypertension and gestational diabetes mellitus during pregnancy, with corresponding negative consequences for health, and is a direct cause of macrosomia, which may alter the child’s glucose and lipid metabolism and trigger hypertension.
- Weight gain during pregnancy
- Insufficient intake of omega fatty acids during pregnancy
- Maternal obesity with deficiency of multiple micronutrients
- Iron deficiency
- Folate and other B vitamins
- Vitamin D
- Deficiency in multiple micronutrients
1. Weight gain during pregnancy
The recommended weight gain during pregnancy for a woman of normal weight is 10-16 kg for those with a normal BMI, 13-18 kg for those who are underweight, 7-11 for those who are overweight and 5—9 kg for those who are obese. Both excessive and insufficient weight gain during pregnancy have negative impacts.
With every additional kilogram that a mother gains over that recommended the risk of the child for being obese during adulthood increases by 8%. A high pre-pregnancy maternal BMI is associated with an even higher risk for obesity than excessive weight gain during pregnancy. Reducing body weight to within the normal range before conception and dietary control to limit weight gain during pregnancy are safe, cost— effective methods for lowering the risk for NCDs.
2. Insufficient intake of omega fatty acids during pregnancy
Intake of w-3 fatty acids has been decreasing during the past 50 years, whereas intake of w-6 fatty acids has increased. The main dietary source of «-3 is oily fish (for example, salmon, trout, sardines and sprats), and those of w-6 fatty acids are sunflower, grape seed and corn oil, as well as poultry fat.
Studies in experimental animals have shown a positive effect of w-3 fatty acids on macrodome, as reduced hyperlipidaemia restores the antioxidant balance and immune function. In humans, w-3 fatty acids reduced the risk for the preeclampsia, reduced the weight of the placenta, stimulated the cognitive development of the child and stimulated linear growth.
Other studies in experimental animals, however, led to the conclusion that a high intake of -6 fatty acids in the maternal diet has a negative effect on regulation of the child’s appetite and energy metabolism.
3. Maternal obesity with deficiency of multiple micronutrients
Obese expectant mothers may be deficient in nutrients, as their diets tend to be unbalanced, with a low micronutrient content. This may have long-term effects on the health of the mother and trigger a risk for NCDs in the child.
Excess maternal body weight during pregnancy and lactation requires an intake of more micronutrients to counteract the changes, including inflammation and oxidative stress, caused by obesity.
4. Iron deficiency
The most common mineral deficiency in pregnant women is of iron, and iron deficiency anemia is the most common type of anemia in this group (hemoglobin < 110 g/L), which may have serious consequences for the mother and the newborn. Anaemia before conception and during the early stages of pregnancy is associated with impaired fetal development, premature birth and low birth weight.
Systemic iron deficiency is more common in obese women than in women of normal weight, possibly because of low dietary iron intake, a greater requirement for iron and/or impaired uptake of iron by obese individuals. An important means of reducing anemia in newborns is to delay cord clamping.
5. Folate and other B vitamins
B vitamins play a significant role in controlling energy metabolism, help to reduce insulin resistance and are important for growth, including development of the nervous system and the brain. A deficit of folic acid (folate) causes anemia and is also associated with neural tube defects, poor fetal development in the antenatal period, fetal malformations, premature birth and low birth weight.
Neural tube defects are among the most common multifactorial hereditary fetal conditions, and use of folic acid supplements before conception can prevent up to 46% of cases. Children born to obese women are more prone to neural tube defects than the offspring of women of normal weight, and children born to obese women in disadvantaged social and economic communities are at even greater risk, as it is highly unlikely that mothers in these communities use dietary folic acid supplements.
Folate deficiency is also a risk factor for cardiovascular diseases. Like other B vitamins, folates participate in the metabolism of homocysteine, which may contribute to the development of atherosclerosis by damaging the inner surfaces of arteries and creating blood clots.
The level of homocysteine depends on genetic factors and the dietary intake of folates, vitamins B6 and B12: higher concentrations of these vitamins in the bloodstream correlate with lower homocysteine levels. Low levels of folic acid are associated with a higher life-long risk for fatal coronary heart disease and infarction.
6. Vitamin D
Obese pregnant women are more likely to be deficient in vitamin D than women of normal weight, as obesity reduces the bioavailability of this vitamin. Fatty tissues require vitamin D (which is fat-soluble) and make use of the maternal reserves; the greater the fatty tissue mass of the mother, the more vitamin D she requires.
Expectant mothers are often advised to take additional vitamin D during pregnancy, especially in the Northern hemisphere, as sufficient maternal vitamin D is required for the development of the fetal skeletomuscular system, brain and immune system. Vitamin D deficiency may have a negative effect on the development of the child’s bone tissue and cause long-term skeletal disorders, such as osteoporosis, irrespective of the postnatal nutrition of the child.
Vitamin D deficiency also increases the risks for fetal growth impairment, low birth weight, neonatal tetanus, hypocalcaemia, cardiovascular disease and diabetes mellitus type | and incurs a lifelong risk for cancer. For the mother, vitamin D deficiency is associated with risks for preeclampsia, premature delivery, insulin resistance, gestational diabetes, dysfunction of the immune system and bacterial vaginosis.
7. Deficiency in multiple micronutrients
Obese women, especially those in disadvantaged social and economic strata, may be expected to be deficient in multiple micronutrients. Most deficits are due to similar factors, i.e. improper diet or uptake and a greater requirement because of excessive fatty tissue. The higher the BMI, the greater the risk for deficiency in multiple micronutrients.
Micronutrients play an important role in controlling energy metabolism and help to reduce insulin resistance; they are important for human growth, including development of the nervous system.