Fertilization failures and abnormal fertilization after intracytoplasmic sperm injection

Area of Science:

• Reproductive Medicine
• In Vitro Fertilization
• Embryology

Background:

• Intracytoplasmic sperm injection (ICSI) is a key assisted reproductive technology.
• Understanding fertilization failure and variability is crucial for optimizing ICSI outcomes.
• Failed and suboptimal fertilization rates after ICSI require detailed investigation.

Purpose of the Study:

• To determine the incidence of failed and suboptimal fertilization after ICSI.
• To analyze variations in ICSI fertilization rates among couples.
• To identify the causes of fertilization failure and abnormal fertilization post-ICSI.

Main Methods:

• Analysis of fertilization rates across 1343 ICSI cycles.
• Longitudinal study of 87 couples undergoing three ICSI cycles with consistent parameters.
• Microscopic examination of unfertilized and abnormally fertilized oocytes using Hoechst 33342 staining.

Main Results:

• Failed fertilization occurred in 3% of cycles; risk decreased with more oocytes injected.
• Suboptimal fertilization (<50%) affected 26% of couples, with only 5% consistently experiencing it.
• Oocyte activation failure was the primary cause of fertilization failure, with sperm head decondensation issues also noted.

Conclusions:

• ICSI demonstrates a low incidence of fertilization failure, influenced by oocyte quantity.
• Most couples exhibit consistent fertilization rates, but a subset shows significant cycle-to-cycle variation.
• Oocyte activation failure and abnormal sperm processing are key factors contributing to ICSI fertilization anomalies.