Obesity and sexually transmitted diseases are cited as the main reasons for rising European infertility.
Currently, estimates say one in seven couples now have trouble conceiving naturally, but Professor Bill Ledger from Sheffield University warned this could rise to one in three.
"Young people of today will become tomorrow's patients in infertility clinics," Professor Ledger said.
He warned the rise in sexually transmitted infections in young teenagers was likely to cause blocked fallopian tubes in some.
"Later, when these young women want to become mothers, they find they can't conceive." Professor Ledger added, "The obese child is almost certain destined to become an obese adult. Many women who are overweight will not ovulate as efficiently."
There is also a potential rise in male infertility, Professor Ledger said. Both the quality and quantity of sperm appeared to be in decline.
