A new study published in The Lancet finds that a daily low dose of aspirin increases the chance of conceiving and having a live birth in women who have suffered a single recent pregnancy loss.
The National Institute of Health researchers write that while many doctors prescribe low dose aspirin to women who have suffered a miscarriage or stillbirth and want to conceive again, there is no substantial evidence to prove this actually works.
Dr. Enrique Schisterman, chief of the Epidemiology Branch at the Eunice Kennedy Shriver National Institute of Child Health and Human Development in Bethesda, MD, and colleagues carried out the study - the largest of its kind - by randomly assigning more than 1,000 women with a history of miscarriage or stillbirth to one of two groups: an aspirin group and a placebo group.
In the aspirin group, the women took a daily low dose of aspirin (81 mg per day) and folic acid, and in the placebo group women took a similar-looking dummy pill plus folic acid.
Doctors recommend folic acid for all women of child-bearing age as it reduces the risk of children being born with neural tube defects, which affect the brain and spine.
The trial was double-blinded, so neither the women nor the doctors who treated them knew whether they were taking the aspirin or the placebo. The women were aged between 18 and 40 and were being treated at four medical centers.
The study followed the women for up to six menstrual cycles while they were trying to conceive, and if they became pregnant, it followed them through the pregnancy. Women who became pregnant stopped taking aspirin at 36 weeks of gestation.
In the study, 13% of the total women who took aspirin and became pregnant subsequently experienced another pregnancy loss, compared with 12% who took placebo. In the end, 58% of the women who took aspirin became pregnant and later gave birth, compared with 53% of women who took placebo.
Aspirin did not help women reduce pregnancy losses overall
In women who had experienced a single recent miscarriage, 62% of women taking aspirin and 53% of those taking a placebo went on to conceive and have live births.
When they analyzed the results, the researchers found that overall, there was no difference in pregnancy loss rates between the aspirin and placebo groups, as Dr. Schisterman says:
"Our results indicate that aspirin is not effective for reducing the chances of pregnancy loss in most cases."
However, further analysis revealed that a subgroup of women who had experienced a single, recent miscarriage (before 20 weeks gestation and within the past year) had a higher rate of pregnancy and live birth while they were on the aspirin treatment.
In this subgroup, 78% of the women on aspirin and 66% on placebo conceived, and 62% on aspirin and 53% on placebo went on to have live births.
While the study did not look into how aspirin might help women conceive, the researchers suggest one reason could be the drug increases the flow of blood to the uterus.
Further research should now be done to see if aspirin might help improve fertility of other women who have problems getting pregnant, such as those whose embryos fail to implant in the uterus.
Meanwhile, Medical News Today recently reported a US study that suggested difficulty getting pregnant could be due to stress. The researchers followed more than 400 women over 12 months and found those with the highest stress levels were more than twice as likely to meet the clinical definition of infertility.