However, in women with one pregnancy loss within the previous 12 months, there did appear to be a benefit.
Jean Wactawski-Wende, PhD, professor in the Department of Epidemiology and Environmental Health in the School of Public Health and Health Professions at the University at Buffalo, is a principal investigator of the Buffalo EAGeR trial and co-author of the study "Preconception low-dose aspirin and pregnancy outcomes: results from the EAGeR randomized trial."
It is published in the current issue of The Lancet.
She points out that many health care providers prescribe low-dose aspirin therapy for women who have had a pregnancy loss, and who would like to get pregnant again.
"The effectiveness of this treatment has not been proven, however, which is why this study was undertaken," she says.
Wactawski-Wende says, "This was a multicenter, double-blind, placebo-controlled trial. It found that, over all, treatment with low-dose aspirin initiated prior to pregnancy does not increase the rate of live births or reduce the rate of pregnancy loss in women with a history of one to two previous pregnancy losses.
"One subgroup studied, those with a single documented loss at less than 20 weeks gestation during the previous year, did experience a higher pregnancy rate and live birth rate, however," she says.
"Our conclusion is that preconception-initiated, low-dose aspirin is not significantly associated with live birth or pregnancy loss in women overall," she says, "and the study does not support the general use of low-dose aspirin to decrease the risk of pregnancy loss."
She says the research team is planning further exploration of these findings to better understand them. That may include studies to explore mechanisms by which the intervention worked by using stored samples of blood and urine collected during the study from these women.
The authors note that the loss of a pregnancy is a fairly common event, estimated to occur in up to 30 percent of all conceptions. Women who have had a pregnancy loss are at increased risk of having a subsequent loss and other adverse pregnancy events.
Wactawski-Wende says that while the pathophysiological mechanisms that lead to adverse pregnancy outcomes are not fully understood, decreased blood flow and increased inflammation are postulated to have important roles.
"Preconception use of low-dose aspirin has been found to improve endometrial growth and vascularization in women undergoing in-vitro fertilization, and to increase blood flow and reduce inflammation in the reproductive organs," she says.
"It was hypothesized, therefore, that preconception-initiated, low-dose aspirin might positively affect downstream pregnancy outcomes during that crucial treatment window. Until now, however, that possibility had not been extensively assessed."
To test the hypothesis, researchers enrolled 1228 women between 18 and 40 years old to participate. Of those, 1078 completed the study.
Participants were randomly assigned to receive either low-dose aspirin or placebo, roughly half to each group. They were followed for up to six cycles during which they attempted to conceive. All women in the study received folic acid.
The outcome was that 308 (58 percent) of those in the low-aspirin group had a live birth, compared with 286 (53 percent) of those in the placebo group. Pregnancy loss occurred in 68 (13 percent) of the women taking low-dose aspirin and in 65 (12 percent) of the placebo group.
Adverse events were similar between the two groups. One adverse reaction, increased vaginal bleeding, was associated with low-dose aspirin but the bleeding was not associated with pregnancy loss.
"Women should talk to their health care providers before considering low dose aspirin or any other medication while attempting to get pregnant or during pregnancy," Wactawski-Wende says. "But based on this trial, general use of low-dose aspirin is not recommended."
This study was funded by the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) of the National Institutes of Health.
The work was conducted by researchers at UB, NICHD and University of Utah Health Sciences Center, in Salt Lake City, Utah; the University of Haifa, in Israel; The Commonwealth Medical College, in Scranton, Pennsylvania; and the University of Colorado, in Denver, Colorado.
Additional UB investigators include Richard W. Browne, PhD, associate professor, Department of Biotechnical and Clinical Laboratory Sciences, School of Medicine and Biomedical Sciences, and Moeen Abu-Sitta, MD, clinical associate professor, Department of Obstetrics and Gynecology, School of Medicine and Biomedical Sciences. Browne and Abu-Sitta are also research associate professors in the Department of Epidemiology and Environmental Health, UB School of Public Health and Health Professions.
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