It costs £1000 for a vial of sperm from a licensed sperm bank, and one vial rarely does the job. But is price the only reason people go to the online fertility marketplaces?

For both Erika and Alex, knowing the other genetic half of their biological children is what took them to the internet's sperm donation marketplace. Erika, founder of the parenting connection site Pride Angel, wanted her child to know the donor. She also wanted the rest of the donor's family to be involved. Meanwhile, Alex recently joined Facebook's online donor groups because he wanted to know the people who will be raising his offspring, and maybe get the opportunity to visit every once in a while.

Shadow donor networks have been around for decades - excluded by clinics because of their sexuality, their marital status, or their desire to know the child - people whispered to friends and friends of friends at dinner parties and lecture halls. But with the dawn of the internet, these networks have expanded. Now, to access them, you simply need a web browser and a social media account.

Dr Aleks Krotoski has been tracking these sperm donor groups since 2018, and has seen both the rewards and the risks. Yes, there is the opportunity to meet a donor and the child's future parent, but this is an unregulated market dealing in a regulated material. Compelled to this underground world, the people who offer and receive put themselves and their future children in danger of exploitation and disease.

In this episode, Aleks asks, just because the internet lets us do it, should we?