There is glycosuria due to increased GFR

Plasma:

i)Total T4* is increased. This is due to increased thyroid binding globulin (TBG). Free T4 usually remains normal

ii)Cortisol* is normally increased. Cortisol binding globulin (CBG) is increased ,free cortisol is probably normal.

iii)Transferrin or TIBC* (Total iron binding capacity) is increased

iv)Iron* is increased

v)Alkaline phosphatase is increased due to placental isoenzyme.

vi)Total protein and albumin is decreased due to dilution by fluid retention.

vii)Decreased concentration of urea and urate due to fetal growth and increased GFR.

Passing glucose in the urine (renal glycosuria) is common both in pregnancy and in women taking oral contraceptives. There is an increase in the glomerular filtration rate (GFR) by about 50% during pregnancy and glycosuria may partly be due to an increased glucose load in normal tubules.

It is important to note that the plasma concentrations of many carrier proteins increases during pregnancy. This might lead to an erroneous diagnosis if this fact is not taken into consideration. However in most cases the rise in concentration of the carrier protein is accompanied by a corresponding increase in the substance bound to it without causing any change in the unbound free fraction. The protein bound fraction is the transport form and is physiologically inactive.It is important to determine the concentration of the free form of some hormones (such as thyroxine) as it is the active form.

Most of these maternal biochemical changes may also be found in newborn infants and in women taking oral contraceptives.

Progressive haemodilution by fluid retained during pregnancy may also account for some of the maternal biochemical changes. The haemodilution is maximal at the 30th week of pregnancy and this leads to a reduced concentration of albumin (and calcium).Calcium is bound to albumin.The low calcium and albumin concentration may be more marked in pre-eclamptic toxaemis, where the fluid retention may be greater than normal.

There is a rise in the plasma alkaline phosphatase activity during the last three months of pregnancy.This is due to the presence of placental isoenzyme and should not be misinterpreted. However there is no increase in the plasma concentration of alkaline phosphatase in the new born as placental alkaline phosphatase does not cross the placenta.

There is low plasma maternal urea and urate concentration due to increased glomerular filtration rate (GFR) and the positive protein and purine balance during growth of the fetus.

References:

Pages 144 to 145. The reproductive system.Chapter 7.Clinical Chemistry in Diagnosis and Treatment. Sixth Edition. Philip D. Mayne