Does sperm freezing affect fertility outcomes in men with obstructive azoospermia?

This study investigated if sperm cryopreservation (freezing) affects fertility outcomes for men with obstructive azoospermia (OA; lack of sperm cells in the semen due to a blockage). 

The authors found that the clinical pregnancy rate (CPR) was lower with the use of frozen vs fresh epididymal sperm. 

There are many possible causes of male infertility (MI). Obstructive azoospermia (OA) is one of these. OA is in a lack of measurable sperm in the ejaculated semen. This is caused by a blockage that prevents sperm traveling from the testes. Sperm is produced by the testicles and stored in a structure on the back of each testicle, called the epididymis (Epi). This allows mature sperm to travel to the penis during ejaculation.

In men with OA, sperm can be harvested directly from the Epi or testes. It then can be used for fertility treatments such as intracytoplasmatic sperm injection (ICSI). This involves injecting a single sperm into a woman's egg to create a fertilized embryo that can be implanted into the woman's uterus (womb). Sperm can be used fresh or frozen. Some studies suggest that there is no difference in fertility outcomes between fresh or frozen sperm. However, it is unclear if fresh or frozen Epi or testicular sperm gives the best fertility outcomes during ICSI.

This study analyzed 20 studies involving men with OA. Men had sperm extracted from either the Epi or the testes and was used fresh or frozen for ICSI. The authors compared fertility outcomes for these men.

Fresh Epi sperm was associated with a 16% higher chance of a clinical pregnancy rate compared to frozen Epi sperm. 44.1% of fresh Epi sperm cycles resulted in a clinical pregnancy compared to 36.6% using frozen Epi sperm. There was no difference in fertilization rate or clinical pregnancy rate with the use of fresh or frozen testicular sperm.

The authors concluded that the use of fresh Epi sperm resulted in an improved pregnancy rate compared to frozen Epi sperm during ICSI in men with OA.

This study analyzed several very different studies. Some data was missing. Female factors were not considered in the analysis. Oocyte (egg) quality and other factors could have impacted fertility outcomes. More controlled studies are needed.