Previous studies have shown that women who use donor sperm and those who get pregnant with a new sexual partner have higher rates of preeclampsia than other women. That suggested that the condition could be related to the body's immune response to cells it doesn't recognise.
So lead author Dr Peter Klatsky, from Women and Infants Hospital in Providence, Rhode Island, and his colleagues wanted to test if that pattern held true for eggs that the body would consider "foreign".
They compared 77 women who gave birth using donated eggs between 1998 and 2005 with 81 similar women who had gotten pregnant using IVF with their own eggs. The researchers noted how many women in each group were diagnosed with either preeclampsia or pregnancy-related high blood pressure during their third trimesters, as well as how many gave birth to their babies prematurely.
The results, published in the journal Obstetrics & Gynecology, show that about 5% of women who used their own eggs for IVF developed preeclampsia, compared to almost 17% of women using donor eggs. Women using donor eggs were also more likely to have hypertension without kidney problems and to deliver early.
The findings also showed that women who got pregnant using embryos that had been frozen and then thawed were more at risk for preeclampsia than women using fresh embryos. While the researchers did not initially set out to test that, Klatsky said it's a possible effect that's worth looking into with future studies.
He also said the findings suggest that doctors may want to keep a close eye on patients who got pregnant using donor eggs to make sure they don't show signs of preeclampsia.
Doctors should counsel patients
Dr Sacha Krieg, an obstetrician who studies infertility at the Kansas University Medical Centre and was not involved with the study, agreed that doctors should counsel patients at increased risk for preeclampsia and monitor them more closely during pregnancy.
But she cautioned against trying to draw too much of a conclusion from a small study. Rather than looking backwards at records of women who have already given birth, she hopes that future studies will start with women who are just getting pregnant and track them prospectively.
What both Klatsky and Krieg do hope is that this study will give researchers more clues about how preeclampsia develops.
Signs continue to point to preeclampsia having something to do with the immune response to foreign cells. That would make sense, Krieg said. "We know that the immune response is important for both implantation and development of the fetus," she said.
Doctors need to learn more about how a fetus implants in the uterus, Krieg added, because this is probably where the early stages of preeclampsia start, even if women don't show symptoms until much later.
The main message of the study, Klatsky said, is that doctors should be aware of possible risks to their patients, and most importantly that researchers should keep tracking the immune system response in pregnant women.
"This is exciting because it sheds new light on to a potential cause of this common disease," he said. (Reuters Health/ November 2010)