Renal adaptation to pregnancy is summarized in Table, ...3..
Table 3 Principal biochemical changes in pregnancy
There is dramatic dilatation of the urinary collecting system during pregnancy. This may be the result of ureteral smooth muscle relaxation induced by progesterone or due to compression of the ureters by the enlarging uterus. Calyceal and ureteral dilatation is more pronounced on the right.
Renal plasma flow is increased by 60 to 80 per cent by the second trimester of pregnancy. Maternal position affects renal plasma flow in the same way as cardiac output; higher values are obtained in the left lateral position. There is a progressive fall in renal plasma flow throughout the third trimester until levels 50 per cent greater than prepregnancy values are reached at term. Glomerular filtration rate also increases significantly, and creatinine clearance rises by about 50 per cent. This results in a fall in the serum urea and creatinine. Protein excretion is increased and the upper limit of normal in pregnancy is taken as 300 mg/24 h.
There is physiological sodium (and water) retention during pregnancy. Eighty per cent of pregnant women develop some edema, particularly toward term, and it is not always a pathological sign. The pregnant woman has a decreased ability to excrete a sodium and water load, and this is most marked near term.
Was this article helpful?