The Midwich Cuckoos

by John Wyndham

Vintage Sci-Fi Series

From the back cover:

A nightmare tale of a quiet English village where nothing ever happened--until late one September night, when every woman in town became inexplicably pregnant...

Nine months later sixty beautiful children were born...sixty unbelievable threats to the human race!

The Midwich Cuckoos (1957) by John Wyndham - Ballantine Books