Implications of Gestational Development

Conception is the result of intricate biology, but the intricacies of biology do not end at that point as the growth and development of the fetus continues within the woman's body for nine months. As the fetus is not a parasite, these required nutrients come directly from the mother's nutrient intake; therefore, proper gestational development of the fetus is directly dependent upon the intrauterine environment that is provided by the mother, and risk of heart disease, diabetes, hypertension, and other health problems during adulthood have roots linked to maternal nutrition during pregnancy.

When maternal intake is unable to facilitate its own survival, thus falling below optimal levels, fetal growth and development are compromised more than maternal health. In general, nutrients will first be utilized by the maternal biology to facilitate her health and physiological changes and then for the placental development and finally to the fetus. To adequately provide the developing fetus with its nutritional requirements, changes occur in the maternal body composition and functions in a very specific sequence as the successful completion of each change depends on the one before it. Critical periods, which are preprogrammed time periods during development when specific cells, organs, and tissues are formed and integrated and functions established can be drastically influenced by the nutritional status of the mother. For optimal growth during these times, it is essential that certain nutrients be available in specific amounts. These critical periods are one-way routes; any errors or lack of development during these periods are irreversible and so cannot be corrected.

Both deficits and excesses in nutritional status during the critical periods can lead to lifelong defects in organ and tissue structure and function. Deficits and adverse prenatal environmental conditions induce adaptive changes that are permanent, promoting survival in the short term, but increasing vulnerability to later environmental stimuli, leading to obesity. Data have shown that maternal undernutrition during pregnancy leads to intrauterine growth restriction in the offspring, who then plays catch-up after weaning and develops metabolic abnormalities later in life including obesity, hyperinsulinemia, and hypertension.

The purpose of developing the ability to store fat was biologically and historically one of adaptation. During times of food shortage, it would be adaptive to be able to store fat for times when food was unavailable. However, in the present day and environment where food shortage is rare, this adaptive feature has turned maladaptive. Many animal models have been widely used as a model to decipher how intrauterine [Page 389]restriction affects obesity and one such study concluded that growth-restricted rat pups demonstrated significant hypoglycemia and hypotriglyceridemia at birth and due to their catch-up growth period, they developed adulthood obesity with evidence of hyperglycemia and insulin resistance. However, if the catch-up period was delayed, those animals resulted in normal adult body weight, hyperglycemia, and postnatal insulin insufficiency. Protein restriction during gestation results in growth retardation which persists even if a normal diet is introduced after birth but if normal diet is introduced during the period of lactation, the pup regains weight, although the accelerated body weight gain continues and leads to obesity. This information can be a useful tool as it points to the lactation period during which interventional means can be implemented to gain proper weight.

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