Low risk of venous thromboembolism following early pregnancy loss in pregnancies conceived by IVF

Adapted from Hansen AT, et al. Hum Reprod. 2018;33(10):1968-1972.

Key Takeaway

  • There is a low absolute VTE risk in the 12 weeks following early pregnancy loss in IVF
  • The relative VTE risk was low for complete IVF pregnancies in comparison to the risk in early gestation.

Why This Matters

  • During the first trimester of IVF pregnancies that leads to delivery, there is an increased risk of VTE
  • This risk is unknown in IVF failed due to early pregnancy loss (implantation failure, missed abortion, or spontaneous or induced abortion before 10 completed gestational weeks)

Study Design

  • A nationwide registry-based cohort study including all Danish IVF pregnancies registered in the Danish IVF Register between 1995 and 2005
  • Exclusion: Women undergoing frozen embryo replacement or oocyte donation
  • Endpoint: Incident VTE (Absolute risk - number of VTEs per 10,000 pregnancies with 95% CI) following IVF pregnancies terminated by either delivery (complete IVF pregnancies) or early IVF pregnancy loss or abortion
  • Follow-up: 12 weeks

Key Highlights

The study identified and included 24,931 women undergoing IVF leading to pregnancy among 19,260 women

  • 16,701 complete IVF pregnancies leading to delivery
  • 7,567 early pregnancy losses before 10 gestational weeks
  • 663 abortions at 10 gestational weeks or later

  • The absolute risk of VTE in IVF pregnancies for early loss and for complete pregnancies was 1.3 [0.03–7.4] and 7.8 [4.1–13.3], respectively, with RR of 0.17 ([0.02–1.3]; P=0.08)


The results do not indicate a need for prophylactic anticoagulant therapy in women suffering early IVF pregnancy loss without other risk factors


  • The study had only a few VTE events available for statistical analyses which limited the precision of estimates
  • Failure in ruling out the occurrence of VTE cases not diagnosed at the hospital
  • Information on the use of prophylactic LMWH was not available

CI, confidence interval; DVT, deep vein thrombosis; IVF, in-vitro fertilization; LMWH, low molecular weight heparin; OHSS, ovarian hyperstimulation syndrome; RR, risk ratio; VTE, venous thromboembolism.

    Hansen AT, Juul S, Knudsen UB, Hvas AM. Low risk of venous thromboembolism following early pregnancy loss in pregnancies conceived by IVF. Hum Reprod. 2018 Oct 1;33(10):1968-1972. doi: 10.1093/humrep/dey271. PMID: 30137318.