Can oocyte activation improve ICSI outcomes?

This study looked at activating oocytes (eggs) with calcium ions prior to intracytoplasmic sperm injection (ICSI). It found that this treatment improves fertilization rates for couples with male infertility, and may improve pregnancy rates.

ICSI is an infertility treatment used when there are few sperm available. It involves injecting a sperm directly into an isolated egg. Roughly 70% of ICSI procedures will result in a successful fertilized embryo. One cause of unsuccessful ICSI is if the oocyte does not activate during fertilization.

Oocyte activation is a complex series of changes which are triggered when a sperm enters the oocyte. These changes prevent other sperm from entering and prepare for development of the embryo. Calcium ions are an important signal which triggers oocyte activation. If the sperm does not prompt the oocyte to release calcium ions, the fertilization will be unsuccessful.

Some researchers have tried to artificially activate the oocyte to increase the success rate of ICSI. This commonly uses calcium ionophores (CAI). CAI are small molecules which can release calcium ions inside the oocyte. It is unclear whether artificial oocyte activation (AOA) with CAI can improve the success rates of ICSI.

This study included 796 couples with infertility. All of the couples had had at least two previous unsuccessful in vitro fertilization (IVF) or ICSI cycles. The couples underwent ICSI with AOA. The researchers used the couples’ previous conventional ICSI or IVF cycle as a comparison.

374 couples with male infertility underwent ICSI with AOA. Compared to the previous cycles, significantly more oocytes were fertilized using AOA for couples with male infertility. Significantly more of the embryos reached day 5 in the ICSI-AOA cycles (56.2% vs. 41.9%). Significantly more AOA cycles resulted in a positive pregnancy test (53.8% vs. 23.9%). Also, significantly more couples with male infertility had a birth with AOA cycles (43.8% vs. 10.9%).

The study also included 307 couples with female factor infertility. These included couples with advanced female age, unexplained infertility, and polycystic ovarian syndrome (PCOS). There was no difference in fertilization rates for these couples. However, the there was a significantly higher rate of embryo implantation and pregnancy using ICSI-AOA.

115 couples had both male and female factor infertility. There was no difference in fertilization rates for these couples. The rate of positive pregnancy test (72% vs. 16%) and live birth (55.3% vs. 12%) were higher using AOA.

This study found that AOA can improve implantation rates from ICSI for couples with male factor infertility. Also, it may improve implantation and pregnancy rates.

It is not ideal to use couples’ previous IVF cycles as a comparison. If the previous cycle had been successful, they would have likely stopped trying to conceive. More studies are needed.