Overall, the risk of a worse outcome for the baby is more than doubled in women with CKD [3].

Before the pregnancy, drugs that may damage the developing foetus should be reviewed. Drugs commonly used in patients with kidney disease that may be teratogenic include angiotensin-converting enzyme inhibitors, angiotensin II receptor blockers, and immunosuppressive drugs such as mycophenolate. The risk of teratogenicity must be weighed against the risk posed to the mother by stopping the drug [4].

The GFR of normal kidneys increases by 50 % over the first 3 months of a pregnancy (Fig. 6.1). In someone with a well-functioning kidney transplant the GFR will increase by up to this amount, proving that this effect is not mediated by the kidney’s nerve supply. If a pregnant woman shows no fall in serum creatinine this is a sign that her nephrons are unable to ‘hyperfilter’ and she is likely to have underlying chronic kidney disease.

Hyperfiltration due to pregnancy can damage already diseased glomeruli. The risk increases in proportion to the stage of CKD before pregnancy, whatever the cause of the kidney disease.

If the eGFR is more than 60 ml/min/1.73 m² the outlook is good, including with a well functioning transplant. With hypertension or proteinuria there is an increased risk of pre-eclampsia and loss of kidney function. Women with vesico-ureteric reflux have an increased risk of urinary tract infections during pregnancy and may benefit from daily prophylactic antibiotics.

If the eGFR is less than 40 ml/min/1.73 m² and there is heavy proteinuria – more than 1 g per day, i.e. protein: creatinine ratio >100 mg/mmol (1000 mg/g) – the rate of decline in GFR is accelerated by pregnancy and the time to end-stage kidney failure shortened [5].

With CKD stages 4 and 5, the likelihood of becoming pregnant is significantly reduced as ovulation is irregular or absent. If conception does occur, the foetus usually does not grow at the normal rate and is either born early or stillborn. Successful pregnancy is a rare but wonderful event in women on dialysis.

Pregnancy itself can cause kidney disease, a condition called pre-eclampsia. This presents with hypertension, peripheral oedema and proteinuria, usually in the last 6 weeks of pregnancy. If it presents earlier than 34 weeks the outcomes are worse. The clinical severity of the kidney disease can vary from just hypertension and proteinuria to severe acute kidney injury requiring dialysis due to thrombotic thrombocytopaenic purpura (TTP) .