How does freezing affect sperm collected through micro-TESE?

This study looked at how freezing affected sperm collected surgically from the testes. It found that frozen sperm and fresh sperm led to similar pregnancy rates from intracytoplasmic sperm injection (ICSI), but that there were more miscarriages when using frozen sperm.

Nonobstructive azoospermia (NOA) is a condition in which there are extremely few sperm in the semen. NOA is not due to a blockage of the tubes from the testes to the penis. There are multiple causes of NOA including hormonal conditions, genetics, undescended testicles, or past cancer treatment. 

Men with NOA often have a few immature sperm in the testes. Microscopic testicular sperm extraction (micro-TESE) is a surgical procedure to collect these sperm. Micro-TESE uses a microscope to locate and collect areas with more sperm. Microscopic guidance also allows the surgeon to avoid areas with blood vessels, which leads to less scarring and inflammation. Sperm collected through micro-TESE can be used with ICSI. This procedure injects a single sperm into each collected oocyte (egg). This allows ICSI to be used with far fewer sperm than a similar infertility treatment, in vitro fertilization (IVF).

Currently, micro-TESE is normally performed on the same day as oocyte collection. This allows the fresh eggs to be fertilized with fresh sperm. However, both partners undergo surgical procedures at the same time. This can be more difficult for both the couple and the infertility clinic. Also, micro-TESE is not always able to retrieve sperm. When it is unsuccessful, the couple has to choose between using donor sperm or preserving the eggs.

It is possible to freeze sperm from micro-TESE. This allows couples to plan ahead for oocyte collection. However, it is not clear whether pregnancy rates after ICSI are equally good using fresh and frozen micro-TESE sperm.

This study used records from 65 men with NOA who successfully underwent micro-TESE, and underwent 70 ICSI cycles. The 65 men who used ICSI were part of a larger group who used micro-TESE. Out of 244 men with NOA who underwent micro-TESE, the procedure successfully retrieved sperm for 35.25% of the men. There were 40 ICSI cycles using fresh sperm, and 30 cycles using frozen sperm. 5 men underwent frozen ICSI after a previous unsuccessful fresh ICSI. The two groups had similar ages and hormone levels.

Out of the 30 frozen sperm samples, 25 had moving sperm after warming. The fertilization rate was significantly higher for sperm which regained movement after warming (69.91% vs. 30.84%). However, the overall fertilization rate was similar for both fresh (65.69%) and frozen sperm (60.12%).

There was a similar pregnancy rate for embryo transfers from fresh and frozen sperm. However, pregnancies fertilized with frozen sperm had significantly more miscarriages (23.81% vs. 0%). Similarly, the birth rate was significantly lower for embryo transfers using frozen sperm (50% vs. 75%).

This study found that freezing sperm after micro-TESE can lead to successful ICSI for men with NOA, but there is a higher rate of miscarriages compared to fresh sperm.

The frozen group included 5 ICSI cycles using extra sperm after an unsuccessful fresh ICSI. Ideally, the two groups of a study should be independent and not include the same patient twice. Infertility treatments are generally more successful for couples who have not previously done the same treatment unsuccessfully.