Research in a 2026 study found that bacteria detected on the embryo transfer catheter were linked to lower live birth rates, likely reflecting the patient’s own microbiome being carried into the uterus during transfer.
Implantation failure
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 review explored why endometriosis surgery doesn’t always lead to pregnancy, highlighting factors like recurrence, undetected lesions, and underlying biological processes that aren’t addressed by surgery.
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 showed that women with unexplained infertility who didn’t get pregnant after IVF had a more diverse endometrial microbiome with fewer Lactobacillus bacteria, and metabolites produced by other bacteria may influence how the uterine lining functions during implantation.
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 2026 study used a machine learning model to predict whether a miscarriage was euploid or aneuploid using routine medical data, without PGT-A, and showed moderate ability to distinguish between the two while identifying several associated factors.
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.
Researchers in a 2025 study showed that women with endometriosis or adenomyosis had lower IVF success overall after 3 IVF cycles, with more differences in the first, fresh transfer.
A 2025 study suggests that acetaminophen (Tylenol), at levels reached after a standard dose, can disrupt embryo development in experimental models, raising questions about its potential impact on IVF outcomes, although better research in humans is needed before changing clinical practice.
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 compared cumulative live birth rates for patients transferring up to 15 untested embryos. Besides the CLBR based on single blastocyst transfers and age, they found differences based on ovarian response and blastocyst formation rates. They also suggested a new way to define recurrent implantation failure.
A 2025 study compared changes in gene expression in the endometrium of women with or without RIF, finding many differences, with most involving immune cell populations.
A 2025 study found that RIF and RPL patients with abnormal EMMA & ALICE results that had antibiotic and/or probiotic treatment showed similar pregnancy rates to those with normal EMMA & ALICE results.
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 2024 study found that patients that have 5 consecutive euploid transfers had a cumulative live birth rate of 98.1%, suggesting that most cases of implantation failure are due to the embryo, and that true unexplained RIF occurs in less than 2% of patients.
Researchers in 2024 detailed a case report of a patient with recurrent implantation failure as a result of bacterial contamination, which was resolved after removal of the zona.
