Tuesday, 3 December 2013

Physiological adaptations in pregnancy - Weight gain, protein and fat metabolism

Weight gain:
Average weight gain during pregnancy is 12.5kg or 27.5lb.
It is attributable to uterus and its contents, breast, increase in blood volume and ECF, increase in cellular water and deposition of new protein and fat.
On average weight gain of 0.5kg/wk from 20 wks occurs.
The weight gain is directly related to birth weight of the fetus.
Increased water retention occurs during pregnancy.
About 6.5 lit of water retention occurs.
In that 3.5 lit of water content will be present in the fetus, placenta and amniotic fluid.
Around 3 lit will be present in maternal blood volume and in the increased size of uterus and breast.
Increased water retention is mediated by fall in plasma osmolality induced by resetting of osmotic thresholds for thirst and vasopressin secretion.

Protein metabolism:
During the second half of pregnancy, about 1000g of protein are deposited amounting 5 – 6 g / day.
In that fetus and placenta contain about 500g, the remaining 500g added to uterus as contractile protein, in breasts primarily in the glands, in maternal blood as hemoglobin and plasma proteins.
 The concentration of most of the aminoacids fall, except glutamate and alanine which will rise.
Albumin concentration decreases due to the hemodilution.
State of positive nitrogen balance occurs.
Pregnancy specific changes are mild fasting hypoglycemia, postprandial hyperglycemia, peripheral resistance to insulin and hyperinsulinemia.
These are ment to ensure sustained postprandial supply of glucose to fetus.
Placental lactogen, estrogen, progesterone, cortisol, placental insulinase contribute to diabetogenic state of pregnancy.
 Insulin sensitivity is 50 – 70 % lower in third trimester.
During fasting, plasma concentration of glucose is lower and that of FFA(free fatty acids), TG(triglycerides) and cholesterol are higher.

Accelerated starvation :
Pregnancy induced switch in fuels from glucose to lipids occurs.
 Ketonemia and ketonuria develop faster in pregnancy.

Fat metabolism:
Storage of fat increases to maximum in mid-pregnancy and decreases in third trimester towards term as fetal demands increase.
Concentrations of FFA, lipoproteins, apolipoproteins, cholesterol in plasma increase.


-Physiological adaptations in pregnancy - anatomical changes
-Physiological adaptations in pregnancy - weight gain, protein and fat metabolism
-Physiological adaptations in pregnancy - electrolyte and mineral metabolism
-Physiological adaptations in pregnancy - respiratory and cardiovascular systems
-Physiological adaptations in pregnancy - GIT, CNS, urinary and endocrine systems

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