More donors are needed at Britain's national sperm bank, its boss has said, as she revealed it has just nine a year after it opened.
It could take around five years before the centre, based at Birmingham Women's Hospital, has enough donors, chief executive Laura Witjens said, but added that she is hopeful more people will sign up.
A change in tack when it comes to advertising could make a big difference, Ms Witjens told the Guardian.
"If I advertised saying 'Men, prove your worth, show me how good you are', then I would get hundreds of donors," she said.
"That's the way the Danish do it. They proudly say, this is the Viking invasion, exports from Denmark are beer, lego and sperm. It's a source of pride."
She said of the hundreds of people who might enquire about donating only a small number may make it through screenings and become a registered donor.
"If 100 guys enquire, 10 will come through for screenings and maybe one becomes a donor. It takes hundreds of guys," she said.
The independent sperm bank is a collaboration between the National Gamete Donation Trust and Birmingham Women's Hospital.
After receiving a £77,000 grant from the Department of Health to help run the centre for the first year it will now be funded independently of the Government.
Once the sperm is collected by the centre it is delivered to clinics across the country when required.
The cost of a sperm sample is £400, but is paid for by the NHS if patients meet the guidelines for free treatment, the Trust said.
Ms Witjens said she hopes one day the centre will have "an abundance of donors", but warned that increasing the £35 for donations was not necessarily the answer.
"We might get more donors if we paid £50 or £100 per donation. But money corrupts. If you feel you can make £200 a week for four months, you might hide things about your health."