The US is no exception.

To tackle this issue the US government announced that it would provide subsidies for Americans seeking IVF treatment. The announcement was accompanied by one suspect sounding stat from US Health Secretary Robert F. Kennedy Jr.

"Today the average teenager in this country has 50% of the sperm count, 50% of the testosterone as a 65-year-old man," he said.

We speak to Professor Allan Pacey, Professor of Andrology at the University of Manchester, and Adith Arun, a researcher at Yale University to find out whether this statement is accurate.

Producer/Presenter: Lizzy McNeill

Series Producer: Tom Colls

Editor: Richard Vadon

Sound Mix: James Beard