Researchers Identify Potential Cause of IVF Failure

Biological process may lead to failure of embryo to attach to uterine wall.

A previously unexamined biological process may be the cause of failure during in vitro fertilization (IVF), a recent study indicates.

IVF carries an approximately 25% success rate due to a significant number of embryos that are unable to attach to the uterine wall. Certain women suffer from recurrent implantation failure, where the embryo transfers but doesn’t attach to the mucus membrane of the uterine wall, which is the stage of IVF where most embryo losses occur.

Women who repeatedly experience this failure have been found to have altered microRNA levels within the endometrium. As a result, researchers from The University of Manchester's Institute of Human Development sought to experiment with varying microRNA-145 levels and the receptor for insulin-like growth factors (IGF1R), which played an unknown role in the attachment process.

The study notes that when IGF1R decreases, the probability that the embryo won't attach to the uterine wall is higher.

"When an embryo is ready for implantation, its replacement is carefully timed to coincide with the window of maximal receptivity in the uterus,” study lead Professor John Aplin said in a press release. "This window is open for no more than 4 days. Our study suggests that the presence of IGF1R during this period is required for the embryo to stick to the uterus."

The study revealed that MicroRNA-145 plays a role in the process as over-expression limits IGF1R growth. The researchers found that varying this level had a direct impact on IGF1R.

While more research is necessary to confirm the results, specifically in the human uterus at the time of implantation, the study indicates that developing treatments to suppress microRNA-145 could improve attachment rates.

"This is one of the hardest groups of women to treat in fertility science and rates are still very low across the board,” Aplin said. “Repeated IVF cycles are stressful and can be expensive too. Greater understanding of the mechanisms which control success or failure can lead directly to treatments to make IVF cycles more efficient so that infertile couples can start their families."