A 2026 meta-analysis explored ways to optimize natural FETs, examining ovulation timing, progesterone use, luteinized unruptured follicles, and cycle variability across natural, modified natural, and newer natural proliferative phase approaches.
Endometrial thickness
A large 2025 study found that a thin lining (<7 mm) lowered live birth rates in medicated and modified natural FETs, but not in natural cycles, and overall endometrial thickness was not a strong standalone predictor of IVF success.
A 2025 study found that live birth rates increased with endometrial thickness up to about 9 mm, after which they plateaued.
Researchers in a 2022 study performed a meta-analysis on the impact of acupuncture on FET outcomes and found that there were improvements in clinical pregnancies but not live birth rates, with most included studies small.
Researchers in a 2022 study compared the impact of endometrial thickness on pregnancy outcomes in fresh and frozen embryo transfer cycles.
