From the Research
For a medicated frozen embryo transfer (FET) cycle, the optimal progesterone level on the day of embryo transfer should be greater than 50 nmol/L, while estrogen levels should be between 100-500 pg/mL, with the most favorable outcomes observed when estrogen levels are between 200-300 pg/mL. To achieve these levels, patients typically start with estrogen supplementation (such as Estrace 2mg orally two to three times daily, or Estradiol valerate injections 6-10mg every 3-5 days) for 12-14 days to build the endometrial lining to at least 7-8mm thickness, as suggested by 1. Once the lining is adequate, progesterone supplementation begins, usually as intramuscular progesterone in oil (50mg daily) or vaginal progesterone (Endometrin 100mg three times daily or Crinone 8% gel once or twice daily), with the goal of achieving a progesterone level greater than 50 nmol/L, as supported by 2. Progesterone is typically started 5-6 days before a day-5 blastocyst transfer or 3-4 days before a day-3 embryo transfer. Blood levels are often checked after 5-7 days of progesterone to ensure adequate absorption. Both hormones are continued through the first trimester (10-12 weeks) if pregnancy occurs, as they support implantation and early placental development until the placenta produces sufficient hormones on its own, as indicated by 3. Monitoring these levels is crucial because insufficient hormone support can lead to implantation failure or early pregnancy loss. Key considerations include:
- Estrogen levels should be maintained between 100-500 pg/mL, with optimal outcomes observed between 200-300 pg/mL, as shown by 3.
- Progesterone levels should be greater than 50 nmol/L, as supported by 2.
- The route of estrogen administration may impact coagulation, with oral estrogen potentially inducing activated protein C resistance, as noted by 4. However, the most recent and highest quality study, 3, provides the most relevant guidance on optimal estrogen levels for medicated FET cycles.