Yes, FERTILITY is a Scrabble word!

Letter values in Scrabble US: F 4, E 1, R 1, T 1, I 1, L 1, I 1, T 1, Y 4.

Is it a valid word?

FERTILITY is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

the ratio of live births in an area to the population of that area; expressed per 1000 population per year
the state of being fertile; capable of producing offspring
the property of producing abundantly and sustaining vigorous and luxuriant growth

Also: birth rate, fertility rate.