New research offers fresh hope of IVF pregnancy where the male has a low sperm count.
Frozen sperm collected from testicular biopsies is as effective as fresh sperm in fertilising an egg through IVF, a study has found.
Experts say the discovery will give couples more options and make their IVF treatments easier to organise.
In the absence of sperm in a man's semen, a biopsy procedure is needed to retrieve some directly from inside the testicle. This can then be used fresh or frozen.
Instead of merging the egg and sperm in a petri dish, a single sperm is then injected into the egg via intracytoplasmic sperm injection (ICSI).
When using fresh sperm, the timing of this procedure has to be carefully coordinated. Frozen sperm offers more flexibility as the man and woman can attend different clinics at different times.
Leader of the study, Kenan Omurtag, from Washington University School of Medicine, said: "The convenience and ease of being able to use frozen sperm taken by biopsy in ICSI offers many advantages over fresh sperm."
Full details are published online by PLOS ONE.
Copyright Press Association 2013