During pregnancy, physiological changes occur which are important in the assessment of medical problems. These include:-
- Reduced peripheral vascular resistance
- Lowered blood pressure
- Increased cardiac output
- Increased GFR
- Reduced plasma creatinine, urea, uric acid
Some renal problems become more severe:
- UTI and pyelonephritis are more common in those with and without prior history – asymptomatic bacteriuria should be treated
- Proteinuria becomes more severe – and hence nephrotic syndrome (this increases the risk of venous thromboembolism)
- Hypertension – usually improves in early pregnancy but blood pressure rises later
Some diseases are unique to pregnant women. These include hyperemesis gravidarum, post-partum HUS, amniotic fluid embolism, but most commonly pre-eclampsia.
A third-trimester systemic disorder usually. More prevalent in first-time mothers, very young or old mothers, multiple pregnancies, previous history, or in those with pre-existing hypertension or renal disease. It is characterised by the triad of oedema, proteinuria and hypertension, but may occur with just one or even none of these typical features.
Blood tests typically show falling platelets and increasing uric acid levels. Defective placentation leads to retarded foetal growth. Acute renal failure, more severe haematological disease, and hepatic dysfunction may develop. Acute fatty liver of pregnancy and ‘HELLP’ syndrome are probably variants of pre-eclampsia. Convulsions (eclampsia) are a late development usually associated with hypertension. Magnesium sulphate is the most effective therapy for eclampsia and may be given prophylactically.
The only effective management is delivery. Anti-hypertensive drugs can be used to protect the mother from extreme hypertension but do not alter the course of the condition.
Acute renal failure in pregnancy
Though now uncommon in the developed world this is is a major contributor to maternal death in developing countries. AKI/ARF is mainly associated with septic abortion and with eclampsia/ pre-eclampsia.
Patients with pre-existing renal disease
The presence of proteinuria or high blood pressure in the first trimester suggest pre-existing renal disease.
Blood pressure may improve and serum creatinine fall in early pregnancy, and these are good prognostic signs. In a few patients (typically with more severe renal impairment and/or hypertension) renal function may be permanently lost during pregnancy.
Worsening renal function, blood pressure and proteinuria in late pregnancy closely resemble the development of pre-eclampsia.
Drug therapy during pregnancy should be changed to agents of known safety so far as possible, and risks versus benefits need to be carefully discussed.
- Patient info on pregnancy and contraception in renal disease (see links to drug info on that page)
- Obstetric renal failure (History of Nephrology blog)