Kidney Patients See Decline in Renal Function With Pregnancy

Daniel M. Keller, PhD

November 22, 2011

November 22, 2011 (Philadelphia, Pennsylvania) — For women with renal dysfunction at the time of conception, pregnancy raises the risk for further loss of renal function, particularly in those with the lowest estimated glomerular filtration rates (eGFR). Sajeda Youssouf, MBChB, from the John Walls Renal Unit at Leicester General Hospital, United Kingdom, reported this finding here at Kidney Week 2011: American Society of Nephrology 44th Annual Meeting.

Dr. Youssouf and colleagues performed a retrospective analysis of data from the United Kingdom Collaboration in Obstetrics and Renal Disease (UK-CORD), which has prospectively collated data from 3 renal–obstetric services since 2003, forming one of the largest such databases in Europe. They identified 44 pregnancies in 40 women with stage 3 to 5 chronic kidney disease (CKD 3–5) at 12 weeks of gestation or earlier. "Just over 50% had CKD 3a; the remainder had more advanced CKD," she said. One woman had CKD 5 at the time of conception.

The researchers defined CKD 3–5 as an eGFR below 60 mL/min per 1.73 m² or a serum creatinine level above 110 μmol/L (1.25 mg/dL). Sufficient data were available on 32 women. A decline in renal function was defined as a 25% rise in serum creatinine from baseline.

The mean age of the mothers at conception was 33 years, and they had a mean eGFR of 43 mL/min per 1.73 m². Mean blood pressure was in the normal range. Follow-up was from 6.5 months to 8 years.

"We found that there was a progressive and persistent decline in maternal renal function during and after pregnancy, with the most marked decline in women with CKD stage 3b, 4, and 5," Dr. Youssouf said. "Two women with CKD 4 or 5 at presentation had end-stage renal disease at 1 year, including 1 who became dialysis-dependent during pregnancy." Approximately 20% of the mothers required renal replacement therapy (RRT).

Worse baseline renal function was associated with a 25% increase in serum creatinine during pregnancy and its persistent increase 6 months after delivery. Women with CKD 3a at the time of conception had relatively preserved renal function.

According to the study abstract, all of the women who had an eGFR of 30 mL/min per 1.73 m² or less had a persistent 25% increase of serum creatinine at 6 months, compared with only 33% of the women whose eGFR was above 30 mL/min per 1.73 m² (P = .385). The risk of requiring RRT was 50% and 15%, respectively (P =.169), in this relatively small cohort.

Baseline Renal Function as a Predictor of Future Renal Function Decline

Parameter eGFR in Women Positive for Parameter
(mL/min per 1.73 m²)
eGFR in Women Negative for Parameter
(mL/min per 1.73 m²)
P value
Going on to renal replacement therapy 39.3 47.5 .083
25% increase in serum creatinine during pregnancy 30.0 46.3 .022
Persistent 25% increase in serum creatinine 6 months postpartum 40.2 51.9 .019

Uncontrolled or treated hypertension or proteinuria predicted an earlier and more persistent decline in renal function. There was also a trend toward more RRT in the hypertensive group.

"This study supports the finding that pregnancy is associated with significant and early decline in renal function in advanced CKD," Dr. Youssouf concluded. "Baseline maternal renal function is key to adverse outcome, and maternal hypertension and proteinuria greater than 1 g/day are associated with a decline in renal function."

Session moderator Areef Ishani, MD, MS, chief of nephrology at the Minneapolis Veterans Affairs Medical Center and assistant professor of medicine at the University of Minnesota in Minneapolis, who was not involved with the study, told Medscape Medical News that "these people are very hard to find without these local renal registries. I think [the researchers] did a great job identifying people at risk for progression of kidney disease... — capturing them and then being able to track them over time."

He believes that kidney disease in pregnancy is more common than is usually perceived. "I think what happens is that we don't capture it, so we don't know it. This is an attempt to capture it. What you want to do is to put this in perspective.... Of an overall number of pregnancies, how many fall into this high-risk category as a result of kidney disease?"

Specific therapies for CKD in pregnancy might come later, Dr. Ishani said.

For now, he recommends that physicians talk with their patients about fetal outcomes and a possible decline in maternal kidney function "around the time of the pregnancy, and longitudinally as well. It's something you'd want to counsel them, particularly prepregnancy."

The study did not have any commercial support. Dr. Youssouf and Dr. Ishani have disclosed no relevant financial relationships.

Kidney Week 2011: American Society of Nephrology 44th Annual Meeting. Abstract TH-OR062. Presented November 10, 2011.


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