Renal disease in pregnancy

Published on 09/03/2015 by admin

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Chapter 54 Renal disease in pregnancy

Michael Flynn

Physiology

In pregnancy there is a rise in renal blood flow and a subsequent rise in glomerular filtration rate (GFR) by up to 50%, which is present from the first trimester. There is a slight fall in GFR in the last 3 weeks of pregnancy. This increase in GFR causes a fall in serum creatinine and urea levels to lower than non-pregnant levels.

Changes in renal tubular function result in a fall in serum urate levels in early and mid-pregnancy, with levels rising again in the third trimester. Similarly, up to 50% of normal women will have glycosuria at some point in pregnancy, as the rise in GFR exceeds the tubular capacity to reabsorb glucose.

Anatomically, in pregnancy the kidney enlarges and the renal pelves and ureters dilate. The right side enlarges more than the left due to the dextrorotation of the uterus.

Urinary tract infections

Acute pyelonephritis occurs in 1%–2% of all pregnancies (seeCh 30).

Chronic renal disease

Pregnancy outcome in chronic renal disease is dependent on renal function and blood pressure before pregnancy.

Mild renal disease is defined as serum creatinine <125 μmol/L preconception. There is usually a successful outcome. Pregnancy usually does not affect the long-term progress of the disease, although proteinuria is common. Hypertension is usually not a feature.

Moderate renal disease is preconception serum creatinine between 125 and 250 μmol/L. Most pregnancies are complicated by intrauterine growth restriction (IUGR) and hypertension. Close monitoring is required. A definite group will have irreversible decline in renal function. The risk is especially in uncontrolled hypertension. The major predictor of permanent decrease in renal function from pregnancy is hypertension and prepregnancy serum creatinine, rather than underlying aetiology. Fetal demise due to uncontrolled hypertension, and prematurity, is higher. Prematurity is secondary to severe pre-eclampsia and IUGR. Women with underlying renal disease have a risk of earlier and more severe pre-eclampsia.

Severe renal disease is serum creatinine >250 μmol/L. Although pregnancy is possible, many women are subfertile due to chronic disease and amenorrhoea. Pregnancy poses a significant risk to mother and baby, and general advice is to avoid pregnancy before renal transplant. There is a tendency to worsen more rapidly in the postpartum.

Management of chronic renal disease in pregnancy

There should be joint management with the renal physician.

Prepregnancy counselling

• Counselling includes general health advice.
• In mild impairment, pregnancy is unlikely to change the underlying disease (except scleroderma and polyarteritis nodosa).
• Control of hypertension is essential.
• Review medications and avoid those contraindicated in pregnancy (including angiotensin-converting enzyme inhibitors, angiotensin receptor blockers and some immunosuppressive drugs).
• Advise on possible pregnancy outcomes.
• Pregnancy is not common among long-term dialysis patients, and there is no advantage to any dialysis route.

Antenatal management

• baseline assessment of serum creatinine, urea, electrolytes, creatinine clearance and 24-hour urinary protein
• ultrasound scan: 18-week fetal morphology assessment
• mid-stream urine specimen to exclude infection
• serial assessment of renal function, and specifically hypertension and superimposed pre-eclampsia
• fetal surveillance in the third trimester
• admission for stabilisation if hypertension severe
• aim: delivery at 38–40 weeks (although preterm delivery is indicated for fetal reasons, substantial deterioration of renal function, uncontrollable hypertension or eclampsia)

Most of the risks of pregnancy are associated with hypertension and superimposed pre-eclampsia.

Nephrotic syndrome in pregnancy

The commonest cause of nephrotic syndrome in pregnancy is pre-eclampsia. Greater than 5 g/day proteinuria is associated with significantly higher perinatal mortality and morbidity. If the nephrotic syndrome is not due to pre-eclampsia, the pregnancy may continue to 38–39 weeks gestation if blood pressure and renal function are near normal before pregnancy and the fetus seems well.

Management includes a high-protein diet and fetal monitoring. Diuretics are contraindicated, as they exacerbate the decreased intravascular volume.

Pregnancy and renal transplant

Incidence. About 2% of women with a renal transplant become pregnant. The success rate of an ongoing pregnancy may be higher than 90%.

There is a 30% chance of developing hypertension, pre-eclampsia, or both. It is likely that pregnancy will not have any long-term effect on survival of allograft.

Prepregnancy advice

Advise to use contraception for 2 years after a transplant, after which immunosuppressive therapy will be reduced to maintenance levels. Neither prednisone nor azathioprine is likely to affect pregnancy and pregnancy is then not contraindicated, provided there is stable renal function and normotension.

Pregnancy

• Immunosuppressive medication should be maintained.
• A glucose tolerance test is indicated.
• There are increased risks of IUGR (20%–40%) and preterm delivery (40%–60%).
• The transplanted pelvic kidney is not injured during vaginal delivery.

Further reading

de Sweit M. Medical disorders in obstetric practice, 3rd edn. Oxford:: Blackwell Science; 1995.

McKay D.B., Josephson M.A., Armenti V.T., et al. Reproduction and transplantation: report on the AST Consensus Conference on Reproductive Issues and Transplantation. American Journal of Transplantation. 2005;5:1592-1599.

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