A growing shortage of sperm donors is having heartbreaking consequences for single women wanting to start a family.

More than four hundred women are on the donation list, and are waiting around two years for assisted conception.

New Zealand law stipulates that men can't be paid for donation, which is said to be one of the reasons behind the shortage.

Fertility specialist Simon Kelly says they need 200 donors to keep up with demand, and sadly it's a race against time for most of the women.

"It's largely borne out of the fact that people are leaving starting families until later," he said. "Age unfortunately has the most impact. This has been increasing in the last few years."

Kelly also points out that there are also problems surrounding privacy.

"Any offspring that results has the legal right to know who the genetic parent is. Some might see that as a bit of a barrier to people donating. In other countries donation is more anonymous."