Researchers in a 2026 study found that natural FETs using donor eggs were linked to higher live birth rates, lower miscarriage rates, and lower rates of some pregnancy complications compared to medicated FETs.
Endometrial receptivity
A 2026 study found that low β-hCG levels (≤50 mIU/mL at 9 days after blastocyst transfer) were linked to much lower live birth rates, and that how hCG rises over time is more predictive of outcome than the initial value.
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.
A 2026 study found that patients with a previous cesarean delivery had slightly lower live birth rates after IVF compared to those with a previous vaginal delivery, though the reason for this difference isn’t clear.
A 2026 study found that if endometrial fluid cleared before embryo transfer, live birth rates were similar to patients without fluid. When the fluid remained, live birth rates were lower, and cancelling the cycle didn’t appear to improve outcomes in a later transfer.
A 2026 meta-analysis found no benefit of ERA or other endometrial receptivity tests in general IVF patients, with a possible improvement in live birth for RIF patients transferring untested embryos.
A small 2025 study found that most pregnancies show detectable hCG by day 6 after a blastocyst transfer, and those that first become positive on day 8–10 have higher rates of biochemical and ectopic pregnancy and a lower chance of ongoing pregnancy.
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 randomized controlled trial found that natural cycle FETs led to higher live birth rates and fewer miscarriages than medicated FETs in ovulatory women with a good prognosis.
A 2025 study found that nearly one in three IVF patients without PCOS or diabetes had insulin resistance, which was linked to lower success rates, but taking metformin before embryo transfer seemed to help.
A 2025 study found that PCX, a surface molecule on endometrial cells, may lead to a shorter implantation window in women with endometriosis and might explain the stickiness of lesions outside the uterus.
A 2025 study found that live birth rates increased with endometrial thickness up to about 9 mm, after which they plateaued.
A new study reviewed how fibroids can compromise the endometrium and prevent embryo implantation, identifying key issues such as disrupted blood flow and vascular changes, abnormal endometrial peristalsis, inflammatory responses, and changes in the microbiome.
Researchers in a 2022 study found no difference in live birth rates in those that transferred embryos by standard timing or timing established by the ERA.
Researchers in a 2022 study performed a meta-analysis to combine the results of 8 ERA studies and found no differences in live birth, pregnancy and miscarriage rates among women who performed the ERA or didn’t.
Researchers in a 2022 study compared timing of euploid transfers and found that 160 h was optimal for modified natural FETs, while they found no optimal time for natural FETs.
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 found no benefit in patients who used the ERA after transferring a single euploid, even when accounting for a history of failed transfers.
The post discusses various frozen embryo transfer protocols, which includes a medicated FET, natural cycle FET (true natural/modified natural), and mild ovarian stimulated FET, along with their scheduling. In addition, it examines whether one FET protocol is superior to another, the relevance of the corpus luteum in medicated vs natural cycle FETs, and optimal progesterone levels.
Researchers in a 2022 study compared the impact of endometrial thickness on pregnancy outcomes in fresh and frozen embryo transfer cycles.