Does increasing estrogen dose during frozen embryo transfer affect pregnancy rate?

Area of Science:

• Reproductive Endocrinology
• Infertility Treatment
• Assisted Reproductive Technologies

Background:

• Hormone therapy frozen embryo transfer (HT-FET) is a common infertility treatment.
• Estrogen administration is crucial for endometrial preparation in HT-FET cycles.
• Optimizing estrogen dosage is essential for maximizing implantation and pregnancy rates.

Purpose of the Study:

• To evaluate the impact of escalating estrogen doses versus a fixed dose on endometrial thickness.
• To compare clinical pregnancy rates between fixed and increased estrogen dose protocols in HT-FET.
• To determine the optimal estrogen regimen for successful HT-FET outcomes.

Main Methods:

• Retrospective analysis of 5452 HT-FET cycles (2008-2021) at a university fertility clinic.
• Comparison of two groups: fixed daily estradiol dose (6 mg) versus an increased-dose regimen.
• Endometrial thickness measured via ultrasound, with clinical pregnancy rate as the primary outcome.

Main Results:

• The increased-dose group received higher total estrogen (122 mg vs. 66 mg) and longer treatment (17 days vs. 11 days).
• Despite higher estrogen, the increased-dose group exhibited thinner endometrium (8.3 mm vs. 9.5 mm) before progesterone addition.
• Clinical pregnancy rates were comparable: 35.8% (increased-dose) vs. 34.1% (fixed-dose), P=0.401.

Conclusions:

• Higher estrogen doses and longer duration in HT-FET cycles did not result in a thicker endometrium.
• Escalating estrogen dosage did not improve clinical pregnancy rates compared to a fixed-dose regimen.
• Current findings suggest that fixed estrogen doses may be sufficient for optimal HT-FET outcomes.