Mother establishes some nutrient reserves to help her later
All vital organs in mothers body increases activity
All changes are controlled by hormones
Physiological adjustments during pregnancy:
Basal metabolism increases by
5% in 1st trimester 12- 15 % in 2nd & 3rd trimester Increase in BMR leads to increase in weight and high metabolic activity of foetal and placental tissue.
Increase in thyroid function increase the BMR Increase in BMR in 2nd half of pregnancy averages to 150 cal/ day
Gastric tone is decreased. Therefore nausea and vomitings are common.
Gastrointestinal motility diminishes and therefore increased absorption of nutrients as the food movement is slow. Absorption of Ca, Fe, vitamin B12 etc is increased
Decreased ability to taste salt – A physiologic mechanism for increasing salt intake.
Increased progesterone level relaxes uterine muscle and allows expansion for foetal growth.
Changes in renal function is seen
GFR (Glomerular filteration rate) is increased and several substances are cleared very fast.
Water is excreted at higher rate in mid pregnancy and
At lower rate in advanced pregnancy
Increased loss of free fatty acids ; decreased loss of calcium and B-complex Vitamins
Blood Composition:
Plasma volume increases by 50% resulting in apparent decreased levels of Haemoglobin.
Red cell mass increases by 20%
The concentration of Hb and PCV falls despite increase in total Hb. This is called as the physiological anemia of pregnancy. Therefore the normal Hb level in pregnancy is 11g/dl.