What is the comparison between modified natural cycle and medicated cycle for In Vitro Fertilization (IVF) frozen embryo transfer in patients with endometriosis?

From the Guidelines

For patients with endometriosis undergoing frozen embryo transfer (FET), a medicated cycle is generally preferred over a modified natural cycle due to better control of the endometrial environment and timing of transfer, as well as the potential to reduce inflammation and pain associated with endometriosis. The medicated approach typically involves estrogen supplementation for 10-14 days until endometrial thickness reaches 7-9mm, followed by progesterone supplementation starting 5 days before embryo transfer. This protocol allows for a more controlled and predictable environment for implantation, which is particularly important in patients with endometriosis, where the inflammatory environment can interfere with implantation success 1.

Some key considerations for medicated cycles in patients with endometriosis include:

• Estrogen supplementation (e.g., estradiol valerate 2-6mg daily or estradiol patches 0.1-0.2mg/day) to promote endometrial growth and thickness
• Progesterone supplementation (e.g., vaginal progesterone 200mg three times daily, or intramuscular progesterone 50-100mg daily) to support implantation and early pregnancy
• Potential use of GnRH agonist pretreatment for 2-3 months before the FET cycle to further suppress endometriosis activity and reduce inflammation
• Close monitoring of endometrial thickness and timing of transfer to optimize implantation success

While modified natural cycles may be suitable for patients with regular cycles and minimal endometriosis, the unpredictability of ovulation timing and potential for endometriosis flares during the cycle make medicated protocols generally more reliable for optimizing implantation success in these patients. However, it's essential to individualize treatment approaches based on patient-specific factors, such as disease severity, medical history, and personal preferences.

From the Research

Endometrial Preparation for Frozen Embryo Transfer

• The optimal endometrial preparation protocol for frozen embryo transfer (FET) is still a topic of research and debate 2, 3.
• Different methods of endometrial preparation, including hormone replacement therapy (HRT) and natural cycle (NC), are used in current practice 4.
• A "back to nature" approach, advocating for an expanded use of natural cycle FET in ovulatory women, has been suggested due to potential maternal and fetal risks associated with HRT 4.

Comparison of Modified Natural and Medicated Cycles

• A study found that prolonged gonadotrophin-releasing hormone agonist (GnRHa) administration before embryo transfer in freeze-all cycles of patients with endometriosis or aberrant endometrial integrin expression resulted in excellent outcomes 5.
• Another study found that clinical pregnancy rates may be improved in a stimulated cycle compared to a programmed one, but the evidence is of low quality 6.
• The use of GnRH agonist compared to without may improve live birth rates, but the evidence is of low quality 6.

Factors Influencing Endometrial Preparation

• The method of endometrial preparation may influence FET outcomes, including implantation rates and fetal safety 4, 3.
• Factors such as ovulation monitoring, luteal support, and exogenous hormone administration route may impact FET outcomes 4.
• The optimal timing of embryo transfer is still a topic of research, with proposed strategies including starting progesterone intake on the theoretical day of oocyte retrieval in HRT and performing blastocyst transfer at hCG + 7 or LH + 6 in modified or true NC 3.

Conclusion is not allowed, so the response will be ended here.