(Reuters Health) - Women who have donated one of their two kidneys have a doubled risk of developing high blood pressure and the potentially-serious complication known as preeclampsia if they become pregnant, according to a new Canadian study.
But the study also found that the problems are usually manageable and the risk is low to begin with. In addition, having just one kidney did not increase the risk of death for the mother or child, and most women had an uncomplicated pregnancy.
The findings are unlikely to dissuade most donors, who are strongly committed to the donation in the first place, the researchers said.
“Most people donate out of love and the risk we’re identifying wouldn’t deter most of them from proceeding with donations,” said chief author Dr. Amit Garg of the London Health Sciences Center in Ontario.
“I’ve talked to some who have actually donated. They feel this is a manageable risk and they’re appreciative that this has been looked at carefully,” he said in a telephone interview. “Ninety percent of these women don’t have this complication. Among the one out of 10 who did have it, it seemed fairly manageable.”
“There were no serious maternal or neonatal outcomes. So in that sense, the study was reassuring,” said Dr. Sindhu Chandran, a kidney and pancreas transplant specialist at the University of California, San Francisco, who was not involved in the study.
“It adds more information than we were currently able to give,” she told Reuters Health by phone.
The findings were published online Friday by the New England Journal of Medicine and reported at the American Society of Nephrology’s Kidney Week 2014 meeting in Philadelphia.
Living donors are an important source of kidney transplants. Of the nearly 30,000 people who donate worldwide each year, about 60 percent are women and at least a third of them have the potential for becoming pregnant, Garg said in a phone interview.
The impact a donation may have on pregnancy “is a very, very common question among potential donors,” he said. “Your kidneys have to work harder than usual. You have to filter 40 percent to 50 percent more. If you don’t have enough kidney reserve to compensate for the demands of pregnancy, it’s possible that your blood pressure will go up,” because the kidneys affect blood pressure.
Until 2004, there was little evidence that donation caused a problem. But then two reports - one from Norway, the other from Minnesota - suggested a risk. However, those studies have been controversial, in part because they compared women before and after donation, and just growing old, by itself, increases the likelihood of developing high blood pressure.
“That’s what prompted our study, to examine those issues more carefully,” Garg said.
So researchers at Canada’s Institute for Clinical Evaluative Sciences, Lawson Health Research Institute and Western University tapped the medical records of 85 donors in Ontario who experienced 131 pregnancies and compared them to the records of 510 women who had not been donors but had a total of 788 pregnancies.
Among the non-donors, 2.2 percent developed high blood pressure during their pregnancy and 2.7 percent developed preeclampsia, a complication where blood pressure rises and there are signs of organ damage, which can cause serious problems for the mother and fetus if not treated.
Among the donors, 5.3 percent developed high blood pressure and 6.1 percent had preeclampsia.
The overall risk was 11.5 percent for donors and 4.8 percent for non-donors.
“Other important maternal and fetal outcomes were not statistically different between the two groups, and there were no maternal or perinatal deaths. Most women had uncomplicated pregnancies after donation,” the researchers concluded.
One limitation of the study was that it did not have information to adjust for obesity, race, actual kidney function or medication use.
“This was a predominantly white group. This is not a diverse population,” said Chandran. “It would be interesting to know what these findings are in a minority population because I think they would be at higher risk for preeclampsia and hypertension anyway. So we want to make sure this type of study is extended to people like that.”
SOURCE: bit.ly/1BqqsIf The New England Journal of Medicine, November 14, 2014.