|*Nudity and Sexual References*
The final episode looks at the challenges facing those people who have coupled up and those who haven't. For many, maintaining a relationship can be as difficult as forming one. The pressures of adult life put couples and their love life under stress. Sex can turn from a thrill to a function. With babies on the agenda, one couple finds the road to pregnancy set against the odds, but can science provide the answer?
Further down the track, people can develop growing pains in the transition from couple to family as the desire for the thrills of a pre-family life drive them to pleasure-seek out of wedlock.
We learn how science not only explains what's happening to our bodies at key sexual moments, but also how it can save the day when parts don't work as they should.
Produced and directed by Bruce Fletcher; executive producer Yavar Abbas for the BBC and the National Geographic Channel.