Treatment option for sperm- or oocyte-related fertilization failure: assisted oocyte activation following diagnostic heterologous ICSI

Hum Reprod. 2005 Aug;20(8):2237-41. doi: 10.1093/humrep/dei029. Epub 2005 Apr 14.


Background: Failed fertilization occurs in 2-3% of ICSI cycles and is mainly due to lack of oocyte activation. Heterologous ICSI of patient's sperm in mouse oocytes allows discrimination between sperm- and oocyte-related aetiologies of activation failure. Assisted oocyte activation (AOA) by Ca-ionophore treatment can initiate fertilization in subsequent therapeutic ICSI. We report on diagnosis and clinical treatment in 17 patients with previously failed fertilization.

Methods: Sperm from patients were injected into mature mouse oocytes. Activation capacity was assessed by 2-cell formation (mouse oocyte activation test, MOAT). When no activation occurred, it was assumed that the spermatozoon was deficient; otherwise an oocyte-related factor was suspected. In a subsequent ICSI cycle, AOA was done by ICSI with CaCl2 followed by a Ca2+ ionophore exposure. Fertilization was checked 16-20 h later. Embryo transfer was on day 2 or 3.

Results: MOAT showed sperm-related activation deficiency in six globozoospermic patients and two patients with extreme oligoasthenoteratozoospermia. One patient with small sperm acrosomes had a normal activation percentage. In eight other patients, the MOAT revealed a relatively normal activation capacity of the sperm, indicating an oocyte-related defect. After AOA, fertilization rates were 77 and 71% in the sperm- and oocyte-related groups respectively. Five pregnancies were achieved in the globozoospermia group and three in cases of oocyte-related activation failure.

Conclusions: Assisted oocyte activation enables normal fertilization and pregnancy in sperm- and oocyte-related fertilization failure.

MeSH terms

  • Acrosome / physiology
  • Animals
  • Calcium Chloride / pharmacokinetics
  • Female
  • Fertilization*
  • Humans
  • Infertility, Female / diagnosis
  • Infertility, Female / therapy*
  • Infertility, Male / diagnosis
  • Infertility, Male / therapy*
  • Ionophores
  • Male
  • Mice
  • Mice, Inbred Strains
  • Oocytes / physiology*
  • Pregnancy
  • Pregnancy Outcome
  • Sperm Injections, Intracytoplasmic*
  • Spermatozoa / physiology
  • Treatment Failure


  • Ionophores
  • Calcium Chloride