They were the series of erotic novels that made women across Kent hot under the collar.

But it looks as if people were too busy reading the Fifty Shades of Grey trilogy to be, well, putting it into practice to make babies.

At least nine months after the racy books began whipping up a frenzy, the birth rate has, to put it bluntly, drooped.

Figures show the number of babies born in April, May and June this year at one Kent hospital have fallen by around 10% compared to records for the same period in 2012.

A total of 1,199 babies were delivered by maternity staff at Dartford's Darent Valley Hospital, compared to 1,329 born in 2012.

Billed as "Mummy Porn", the tales of mysterious Christian Grey and his sizzling relationship with innocent literature student Anastasia Steele ensured Fifty Shades of Grey became the UK's fastest-selling paperback of all time, even surpassing the Harry Potter series.

A staggering 200,000 copies a week were being bought in Britain this time last year and it became the first book to sell more than a million copies on Kindle.

The trilogy by British author E L James included Fifty Shades Darker and Fifty Shades Freed.

Pregnancy and parenting websites predicted there would a baby boom as a result.

However, the fall in the birth rate has puzzled hospital staff.

The birth rate has steadily risen over the past three years, with 5,272 babies born at Darent Valley from April 2012 to March 2013; 5,003 during the same period in 2011/12 and 3,907 in 2010/11.