Infertility rates 'have hardly changed since 1990'

New research has discovered that worldwide infertility rates have barely changed over the past two decades.

A team of scientists led by Gretchen Stevens from the World Health Organization analysed data from 190 countries from 1990 to 2010.

The results, published in PLOS Medicine, show that almost 50 million couples were unable to have a child after five years of trying in 2010.

This was only a 0.1 per cent decrease on primary infertility rates (where couples are unable to achieve any live births) when compared with 1990 and a 0.4 per cent increase in secondary infertility levels (where women who have previously given birth are unable to have another baby).

Primary infertility was also found to vary from country to country, being more likely in North Africa and the Middle East than in Latin America and the Caribbean.

"The methods used and results presented here provide valuable insights into global, regional and country patterns and trends in infertility," concluded the study authors.

According to the National Institute of Environmental Health Sciences, a woman's fertility begins to gradually decline after the age of 27 before dipping more dramatically after she is 35.