Physiological Changes (cont.)

As a result of all these changes there is a big increase in the amount of blood circulating through the body. The womb enlarges to accommodate the growing fetus. The hormones change the levels of sugar and other blood contents, so as to make it easier for the placenta to take what it needs to feed the fetus. Some hormones relax the womb and other muscles, so that the fetus can squeeze into the pelvis for delivery. A more detailed outline of what happens in pregnancy is set out below.

Physiological changes in the mother - more technical information.

In the mother there is an increase in the renal tubular reabsortion of salt (sodium), which plays an important role in regulating fluid volume. The excretion of sodium is regulated by many factors, which include the effect of hormones such as progesterone, aldosterone from the adrenal gland, and the natriuretic hormones e.g. Arginine-Vasopressin (AVP). The metabolic changes in pregnancy create a tendency towards a low potassium level (hypokalaemia), but this is balanced by the potassium sparing effect of progesterone. Serum uric acid levels are decreased because renal clearance is increased during pregnancy, and renal tubular reabsorption is reduced.

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