Female kidney donors double their risk of developing preeclampsia during pregnancy, according to the results of a Canadian study published in the Nov. 14 edition of the New England Journal of Medicine. While preeclampsia can pose serious health threats to the mother and fetus, the condition is usually manageable, and most women had uncomplicated pregnancies following nephrectomies.
"Most people donate (a kidney) out of love, and the risk we're identifying wouldn't deter most of them from proceeding with donations," chief author Dr. Amit Garg of the London Health Sciences Center in Ontario told Reuters.
Previous studies about pregnancies following kidney donation have yielded conflicting findings about the health of the mother and fetus. A 2004 international conference determined that kidney donation posed no threat to future pregnancies. However, subsequent American and Norwegian studies found a correlation between increased gestational hypertension and preeclampsia among women who donated kidneys before becoming pregnant.
Because there are conflicting findings, some transplantation programs have not included the potential risks with predonation informed consent guidelines.
"We conducted this study to determine whether donors have a higher risk of gestational hypertension or preeclampsia than do nondonors with similar indicators of baseline health," the Canadian study's authors wrote in the study's introduction.
The retrospective, matched-cohort study compared the pregnancies of 85 living kidney donors with 510 healthy nondonors. Kidney donations could have occurred between 1992 and 2010, and the average time between kidney donation and pregnancy was four years.
Researchers matched six eligible nondonors to each donor on the basis of baseline characteristics that might be associated with the risk of gestational hypertension or preeclampsia, including:
- Age at time of cohort entry
- Urban or rural residence
- Income
- Number of prior pregnancies carried to at least 20 weeks
- Time to the first birth after cohort entry
The only significant finding was the occurrence of gestational hypertension or preeclampsia among living kidney donors. Fifteen of 131 donor pregnancies (11 percent) experienced preeclampsia while 38 of 788 nondonor pregnancies (5 percent) experienced the condition.
The rates of preterm birth between the two groups were virtually identical with 8 percent for donors and 7 percent for nondonors. Incidents of low-birth-weight babies was similar at 6 percent for donors and 4 percent for nondonors. Additionally, there were no maternal deaths, stillbirths or neonatal deaths among donors.
The study did not identify a reason for an increased risk of gestational hypertension among kidney donors. However, the study's authors did say increased urine protein following donation can occur, which could lead to a diagnosis of preeclampsia.
Regardless, the study's authors say even though the chances of serious maternal or fetal complications following kidney donation is low, potential donors should be warned about the risk of gestational hypertension or preeclampsia prior to donation.
"Although there is some uncertainty regarding the true magnitude of risk, having reviewed all the evidence and associated limitations, we believe it is conscionable to act," the authors wrote in the study's conclusion. "Information on this potential risk (gestational hypertension) should be included in clinical practice guidelines, shared in the informed-consent processes for potential donors and their recipients when a woman has reproductive potential, and used to guide the care of pregnant donors."
The study was funded by Canadian Institutes of Health Research and others.
