[citation needed] While working with Robert G. Edwards at Bourn Hall Clinic, Cambridge, Cohen reported results in the freezing and successful thawing of a human blastocyst for in vitro fertilization.

[4] At the same clinic, he developed methods to treat male factor infertility using in vitro fertilization (IVF) and co-cultured human embryos with helper cells to promote growth.

[9] He attended the Erasmus University Rotterdam, where he obtained a PhD degree in Medicine in 1982, for his thesis "Interaction between human spermatozoa and hamster oocytes".

[10] In 1982, Cohen joined Bourn Hall Clinic as an embryologist, working with Patrick Steptoe and Robert G. Edwards on techniques to improve human conception through in vitro fertilization (IVF).

He developed a precursor technique of Intracytoplasmic Sperm Injection (ICSI), now used for the treatment of nearly all male factor infertility diagnoses.