Chronic kidney disease and pregnancy: risks, planning and care

In a healthy pregnancy the kidneys work harder. A review in the International Journal of Women's Health explains that glomerular filtration rate increases by roughly 50 per cent, creatinine falls and protein leaks slightly more into the urine. As a result, formulae that estimate GFR from creatinine are inaccurate in pregnancy, which is also acknowledged in NICE's guideline on chronic kidney disease. A creatinine that looks normal for a non-pregnant adult can therefore hide a real loss of function.

The NHS describes chronic kidney disease as a long-term condition in which the kidneys do not work as well as they should, often with no symptoms in the early stages. Many women only learn they have reduced function through a blood or urine test, sometimes first in early pregnancy.

The same review states that any maternal chronic kidney disease increases the likelihood of adverse maternal and fetal outcomes, with risks compounded by advancing stage, hypertension, proteinuria and other conditions. Complications, chiefly pre-eclampsia, increase with the severity of kidney disease and may occur even with normal eGFR. Pregnancies in stage 4 to 5 disease are the most challenging, with hypertensive disorders and preterm birth affecting most.

A meta-analysis in that review found no overall association between pregnancy and deterioration of kidney function, though few of the included women had advanced disease. For women with stage 4 to 5 disease the review reports that a fifth experience a shift in stage or the need for kidney replacement therapy, and it notes that outcomes depend more on stage, proteinuria and hypertension than on the underlying cause. Autosomal dominant polycystic kidney disease increases the risk of pre-eclampsia and urinary tract infection, and diabetic kidney disease adds risks of its own.

The reviews describe preconception counselling as a core step: discussing risks and outcomes, optimising control of the underlying kidney disease and blood pressure, changing medicines, choosing the timing of conception and drawing up a pregnancy care plan. In a British survey described in the review, preconception counselling in a joint kidney and obstetric clinic helped decision-making for nearly all participants, and few found it intimidating.

Reliable contraception matters until the time is right, particularly while medicines that are harmful to a baby are still being used, and options are chosen with the kidney team because oestrogen-containing methods are unsuitable for some people with high blood pressure or other conditions.

• ACE inhibitors and angiotensin receptor blockers are generally stopped because of risks to the baby, with safer blood-pressure medicines substituted.

• Immunosuppressants such as tacrolimus, ciclosporin, prednisolone and azathioprine are commonly used and considered reasonably safe, whereas mycophenolate mofetil increases early pregnancy loss and birth defects and should be stopped before conception.

• The NHS lists long-term regular use of anti-inflammatory painkillers (NSAIDs) among causes of kidney disease, so check with a pharmacist before buying any over-the-counter pain relief.

NICE guidance on hypertension in pregnancy advises that women at high risk of pre-eclampsia, including those with chronic kidney disease, take aspirin from 12 weeks until birth, and notes that aspirin for this purpose must be prescribed. Care is usually in a unit with high-risk obstetric and renal expertise, with frequent review of blood pressure, kidney function, urine protein and baby growth.

Diagnosing pre-eclampsia in someone with kidney disease is difficult because worsening blood pressure and protein loss may come from either condition. Some centres use blood tests for placental markers to help tell them apart, and management follows the same principles as for pre-eclampsia in anyone, with careful postnatal follow-up.

Pregnancy is less common on dialysis, but it does happen. The review reports that since the late 1990s live birth rates have risen to 70 to 90 per cent with more intensive dialysis, although high blood pressure, pre-eclampsia, excess amniotic fluid, growth restriction and prematurity remain common. Intensive haemodialysis, with longer or more frequent sessions, is now the usual model of care.

Fertility improves after a kidney transplant. The review recommends waiting one to two years after transplantation, provided graft function is stable and blood pressure controlled, before conceiving. Tacrolimus, ciclosporin, prednisolone and azathioprine are considered reasonably safe, but pre-eclampsia, preterm birth and growth restriction remain more frequent than in the general population.

NICE advises that women who had pre-eclampsia and still have protein in the urine at 6 to 8 weeks after birth are reviewed at around three months to assess kidney function, with referral for specialist assessment if results are abnormal. Breastfeeding should be discussed well before delivery: the review says all antihypertensive medicines used in pregnancy are suitable, plus enalapril, captopril and quinapril, and that the benefits for a preterm baby may outweigh theoretical risks.

Contraception counselling continues after birth, and long-term follow-up with the kidney team is part of ongoing care. Seek prompt help for severe headache, visual disturbance, pain under the ribs, reduced urine output or swelling that appears suddenly.