Oh, by the way . . . Should I take aspirin to prevent preeclampsia?

Janet, a new prenatal patient, is a 38-year-old G1 P0. You first met her 6 months ago when you performed a routine gynecologic visit, and you noted her blood pressure to be 132/90. You had told her then that she should follow up with her internist. As you complete her medical history and physical exam, you note that her blood pressure remains somewhat elevated at 130/85. As you're walking to the door, Janet asks, "By the way, I've searched the Internet, and given that my blood pressure is a little high and that this is my first pregnancy, wouldn't it be a good idea for me to take a baby aspirin to prevent preeclampsia?"

PREECLAMPSIA COMPLICATED 4% OF ALL DELIVERIES in 2002 and affected nearly 164,000 US women.¹ It is a multisystem disorder in which profound derangements of renal, hepatic, cardiovascular, and central nervous system function are caused by vasospasm.² Eclampsia, defined as seizures in a woman with preeclampsia not attributable to other causes, occurred in 1/278 pregnancies.²

Taking a closer look at the aspirin research

Much hope has been placed on the potential preventative effects of low-dose aspirin, which selectively inhibits thromboxane, a vasoconstrictive prostanoid overproduced by the placenta and platelets of women with preeclampsia. Although large, well-done randomized trials showed no benefit, the Cochrane group assessed the safety and effectiveness of antiplatelet drugs like aspirin.⁹ The review, which included 51 trials with over 36,000 high- and low-risk women, concluded that aspirin or other antiplatelet drugs reduced in the rate of preeclampsia by about 20% (RR, 0.81; 95% CI, 0.75–0.88), preterm birth by 7% (RR, 0.93; 95% CI, 0.89–0.98), and perinatal death by 16% (RR, 0.84; 95% CI, 0.74–0.96). The analysis estimated that 69 women would need to be treated to prevent one case of the disorder.⁹ Nevertheless, ever-optimistic investigators still clung to the hope that a subgroup analysis, especially that of very high-risk women, would show a more dramatic effect.

With that in mind, the PARIS (Perinatal Antiplatelet Review of International Studies) collaboration was formed to do a systematic review and meta-analysis based on individual patient data to assess the value of antiplatelet agents for the primary prevention of preeclampsia and to explore which women are most likely to benefit from such treatment. The findings of the PARIS group, recently reported in Lancet,¹⁰ found that the diagnosis of preeclampsia and the number of infants born before 34 weeks' gestation were both 10% lower with aspirin (95% CI, 3%–16% and 2%–17% lower, respectively). It's likely this new study prompted Janet's interest in taking aspirin.