'Women on Dialysis Want to Get Pregnant'; Rates Higher Than Thought

Women on dialysis get pregnant more often than previously thought, but the rate of live births among them is low compared with the general population, a new American study indicates.

There are also important differences in pregnancy rates by race, age, cause of end-stage kidney disease (ESKD), type of dialysis, and length of time on dialysis, the research shows.

"This study improves our understanding of factors associated with pregnancy and live births" among women on dialysis, says lead author Silvi Shah, MD, assistant professor of nephrology, University of Cincinnati, Ohio.

"[What it] tells us is that for every 1000 women on dialysis each year, pregnancies occurred in 18 women, so pregnancy is not uncommon in women who are on dialysis," she told Medscape Medical News in an email.

"But since pregnancy in these women is high risk and associated with adverse maternal and fetal outcomes, pre-pregnancy counseling is important and should be done by all kidney healthcare providers," she stressed.

The study was published online September 26 in the Journal of the American Society of Nephrology.

Large Cohort of Women Receiving Dialysis in the United States

Because data are so scarce for pregnancy in women undergoing dialysis, Shah and colleagues examined the rates, racial differences, and factors associated with pregnancy in this high-risk population.

They identified 47,555 women between the ages of 15 and 44 years registered with the United States Renal Data System who were on peritoneal or hemodialysis at any time between January 2005 and December 2013.

All women had Medicare as their primary payer.

Out of this large cohort, investigators identified 2352 pregnancies for a pregnancy rate of 17.8 per 1000 person-years, "a higher rate than seen in previous studies," the researchers point out.

There were significant racial differences in pregnancy rates, the highest rates being in Native American women followed by Hispanics and blacks compared with white women.

Likelihood of Pregnancy on Dialysis, Ethnic Group vs White Women

Ethnic Group	Likelihood of Pregnancy, %	Hazard Ratio (95% CI)
Native Americans	77	1.77 (1.33 - 2.36)
Hispanics	51	1.51 (1.32 - 1.73)
Blacks	33	1.33 (1.18 - 1.49)

"The rates found in our study in the dialysis population were consistent with the national pattern in the general population for these three racial/ethnic groups," the investigators note.

Age, Type of Dialysis, and Cause of Dialysis Associated With Pregnancy

Younger age, hemodialysis as the dialysis modality, and ESKD caused by malignancy, glomerular nephritis, vasculitis, and hypertension were all associated with a higher likelihood of pregnancy. Patients with diabetes as the cause of ESKD had the lowest pregnancy rates.

For example, women between age 20 to 24 years had the highest pregnancy rate, at 40.9 per 1000 person-years, whereas women between age 40 and 44 years had the lowest pregnancy rate, at 6.9 per 1000 person-years, Shah and colleagues report.

And women receiving peritoneal dialysis were 53% less likely to become pregnant than women on hemodialysis, at a hazard ratio (HR) of 0.47.

"The reasons for the lower rates of conception in women on peritoneal dialysis remain unclear," the researchers say, "especially because patients with peritoneal dialysis are generally healthier and have higher residual renal function than women on hemodialysis."

But it could be that hypertonic dextrose solutions and the presence of fluid in the peritoneal cavity interfere with ovum transit to the uterus, so "it may be reasonable to switch women on peritoneal dialysis to hemodialysis if a pregnancy is desired," they suggest.

Time on dialysis also had an impact, with those on it less than a year being the most likely to become pregnant.

Women who had been on dialysis for 1 to 3 years were 21% less likely to become pregnant, and those on it for 3 years or more were 33% less likely to become pregnant, relative to women who had been on dialysis for less than a year.

"The findings underscore the importance of better residual renal function, which is associated with higher frequencies of conceptions and more successful pregnancies," Shah and colleagues say.

Pregnancy Outcomes Poor — Live Birth Rate Only 30%

"The live birth rate for women on dialysis in our study was low at about 30%," Shah acknowledged.

This is lower compared with the national average for live births, which is over 60%, she noted.

The low rate of live births in the current study — which contrasts with those of other studies that have shown live birth rates of 40% to 50% among women on hemodialysis — might be partially explained by the higher percentage of unknown outcomes, at 31%, she suggested.

Still, many women who became pregnant in the study had a spontaneous abortion, at over 29%, close to 3% experienced a stillbirth, and about 8% underwent a therapeutic abortion.

These findings could lead healthcare providers to encourage conception before dialysis in women of child-bearing age, with a proper dialysis preparation as needed, the investigators say.

However, Shah noted: "It seems childbearing is critical in a woman's life and women — irrespective of whether they are on dialysis or not — may want to get pregnant."

"It requires a multidisciplinary team to take care of pregnancy for women on dialysis and the critical thing here is pre-pregnancy counseling and discussion of a [woman's] reproductive health by nephrologists," she concluded.

The authors have reported no relevant financial relationships.

J Am Soc Nephrol. Published online September 26, 2019. Abstract

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