Low-dose oral contraceptive effects on thromboelastogram criteria and relationship to hypercoagulability

Objective: The study was undertaken to assess hypercoagulability, by using thromboelastography, in women who use low-dose oral contraceptives (OCs). Study Design: Forty-three women using low-dose OCs (≤35 μg ethinyl estradiol) underwent thromboelastography before starting OCs and again during the third month of OC use. Prior and 3-month mean values of four thromboelastogram parameters (maximum amplitude [MA], K time, α angle, and R time) were compared by using paired t tests. Comparison according to progestin type was also performed with unpaired t tests. Results: Prior versus 3-month values for MA, α, and K were not significantly different (P values-K: 0.8; α: .34; MA: 0.49); power was adequate to detect small differences. The 3-month R time was decreased compared with pre-OC values (P = .025), although the magnitude of this change was not characteristic of hypercoagulability. Comparison according to progestin type demonstrated no difference. Conclusion: We found no significant trend toward hypercoagulability in women who used low-dose OCs and who otherwise had no known thromboembolic risks. (Am J Obstet Gynecol 2003;189:43-7.)