MATERNAL SERUM THROMBOXANE B-2 REDUCTION VERSUS PREGNANCY OUTCOME IN A LOW-DOSE ASPIRIN TRIAL

OBJECTIVE: Our purpose was to determine whether in a low-dose aspirin trial a longitudinal decrease in maternal serum thromboxane B-2 is ass ociated with improvement in pregnancy outcomes. STUDY DESIGN: A total of 606 healthy nulliparous women with singleton gestations were random ized at 24 weeks to either 60 mg of aspirin or a placebo. Maternal ser um thromboxane B, was measured at randomization, at 29 to 31 weeks, at 34 to 36 weeks, and at delivery. After delivery, and without knowledg e of patient outcome or group assignment, patients were categorized as having had either a longitudinal twofold or greater (greater than or equal to 50%) or less than twofold reduction (< 50%) in thromboxane B- 2 from baseline levels at randomization. RESULTS: Of 606 entrants, 92% had sufficient thromboxane B-2 determinations to allow categorization . Whether patients were assigned to aspirin or placebo, birth weight w as significantly greater in women who had a twofold or greater reducti on in maternal serum thromboxane B-2 levels. When the aspirin and plac ebo groups were combined, women with a twofold or greater reduction in thromboxane B-2 levels had less preeclampsia, 1.9% (6/314) versus 5.7 % (14/244) (p = 0.016), less preterm delivery (5.7% VS 10.7%, p = 0.03 2), fewer small-for-gestational-age newborns, 9 of 314 (2.95) versus 1 7 of 244 (7%) (p = 0.023), and a higher mean birth weight, 3314 gm ver sus 3121 gm (p = 0.0001). CONCLUSION: Women with a twofold or greater longitudinal reduction in maternal serum thromboxane B-2 had less pree clampsia and prematurity, fewer small-for-gestational-age newborns, an d higher birth weights than women with less than a twofold reduction.