[Kidneys, hypertension and pregnancy. I. Renal function in normal pregnancy (author's transl)].

Pregnancy enhances renal functioning. As early as the first week of amenorrhoea, renal plasma flow (RPF) and glomerular filtration rate (GFR) increase by 30 to 50%, with parallel rise in creatinine and urea clearances. The water and salt balance becomes strongly positive. However, the normal mechanisms of NaCl retention (aldosterone, desoxycorticosterone, oestrogens) remain active, counterbalancing the natriuretic effects of progesterone and of increased filtered sodium load. Renal regulation of the acid/base equilibrium is preserved, albeit adjusted to a higher pH threshold. At the beginning of pregnancy uric acid clearance is increased and tubular reabsorption of glucose is decreased. Blood pressure falls by 20 mmHg during the first semester. Prostaglandins and progesterone oppose the vasopressive action of angiotensin in pregnant women, and changes in their metabolism may account for the development of pre-eclampsia.