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“For women at high risk for preeclampsia, available evidence indicates modest effects but important benefits of daily low-dose aspirin for prevention of the condition and consequent illness.”
A systematic review conducted by the U.S. Preventive Services Task Force (USPSTF) for the Agency for Healthcare Research and Quality (AHRQ) and published today in Annals of Internal Medicine found that low dose aspirin beginning as early as the second trimester of pregnancy may prevent negative health outcomes. Taking low dose aspirin was found to show no harm to the mother or baby, although understanding of long-term effects is still limited. The Task Force’s purpose was to review the evidence for benefits and harms of low-dose aspirin for preventing morbidity and mortality from preeclampsia.
Eleni Tsigas, Executive Director of the Preeclampsia Foundation, the national patient advocacy organization representing women affected by hypertensive disorders of pregnancy, responded to this draft recommendation, “The best available evidence suggests that women at highest risk for preeclampsia should consider taking daily low-dose aspirin beginning late in the first trimester (by 13 weeks). Taking aspirin does not guarantee prevention of preeclampsia, but it is one more thing that women can do with relative safety to reduce their risk.”
The review took into account studies with relatively large sample sizes that revealed absolute risk reductions of up to 5% for preeclampsia, intrauterine growth restriction and preterm birth. A grasp of absolute versus relative risk is necessary to understand these statistically significant but fairly small effects.
“This may represent a very small effect for everyone, or – more likely – a larger effect in a very small number of women,” said Dr. Thomas Easterling, Director of the Foundation’s Medical Advisory Board. “These results highlight the need for more work – more research, more funding. Out of some 30,000 randomized subjects we report a 2-5% reduction in the rate of preeclampsia. That’s no where near good enough.”
Recent guidelines issued by the American College of Obstetricians and Gynecologists (the College) also recommend low-dose aspirin, but rated the quality of evidence as “moderate” and the recommendation as “qualified.” This means that the healthcare provider and patient should decide together if a low-dose aspirin regimen is in the patient’s best interest. The College’s guidelines also encourage aspirin dosing to begin in the first trimester, in contrast to the USPSTF review that suggests second trimester.
AHRQ’s mission is to improve the quality, safety, efficiency and effectiveness of health care for all Americans. The USPSTF is an independent panel of non-Federal experts in prevention and evidence-based medicine and is composed of primary care providers (such as internists, pediatricians, family physicians, gynecologists/obstetricians, nurses, and health behavior specialists). The USPSTF conducts scientific evidence reviews of a broad range of clinical preventive health care services (such as screening, counseling, and preventive medications) and develops recommendations for primary care clinicians and health systems. These recommendations are published in the form of "Recommendation Statements."
Members of the Preeclampsia Foundation’s Medical Advisory Board (Drs James Roberts and Baha Sibai) provided expert review of the report.
What Are the Risks?
Other notable inclusions in this report include the evaluation of harms of aspirin treatment to mother or baby, which found:
No studies have followed the offspring of preeclamptic women on aspirin beyond 18 months.
“The long-term effect of aspirin usage during preeclamptic pregnancies is actually one of the things we’re collecting in The Preeclampsia Registry,” said Tsigas about the Preeclampsia Foundation’s patient registry. “We’d like to see how offspring of women who took aspirin during their pregnancies fare many years down the road. There’s no published data on this question.”
What Are the Benefits? And for Whom?
The USPSTF authors also concluded that preventing preeclampsia could reduce medical intervention in pregnancy and delivery. Preventing poor perinatal health outcomes could also reduce posttraumatic stress disorder (PTSD) and postpartum depression (PPD), since preeclampsia is associated with poor psychosocial outcomes.
The optimal target population for this intervention are women at higher risk for preeclampsia. However, as the review acknowledged, tools to assess individual risk for the condition and to identify subgroups of mothers most likely to benefit are still needed. The College recommendations, for instance, more narrowly defined the “high-risk population” as women with preeclampsia in at least one previous pregnancy or with prior early preterm birth, but this definition of high risk is not universally used.
What Can You Do?
Women should discuss their individual risk of preeclampsia with healthcare providers properly trained to evaluate them. It’s important for healthcare providers to appreciate that women are eager to do what they can – safely and effectively – to prevent preeclampsia.
We also encourage you to review and submit comments on the draft recommendation statement, now through May 5, 2014 on the USPSTF Web site. Outside input will help to ensure that the final recommendation is valid, reliable, and useful to health professionals, patients, and family members.