Stress and fertility - bad friends

Cognitive behaviour therapy (CBT) can counter this by helping women to "make molehills out of mountains", the researchers said.

Many of the women seen by the team were perfectionists - whether they had high-powered jobs or stayed at home - leading to high levels of stress, BBC reports.

Five to 10% of women are not having periods at any one time, and a much larger population will be sub-fertile.

They had previously found a close relationship between levels of stress hormones and reproductive hormones.

Their preliminary study focused on 16 young women who had not had a period for six months, even though some already had children.

Speaking at the annual meeting of the European Society of Human Reproduction and Embryology in Prague, Prof Berga said that people suffering stress often do not notice or admit to it. "These women didn't report feeling stressed. But when we spoke to them it was clear that they tend to have a loss of perspective, they think they can get more done in a day than is realistic and their sense of self-worth is linked to their achievements at work," said Prof Berga, according to Guardian Unlimited.

The women had been shown to have increased levels of cortisol, a hormone linked to stress.

Over the course of the study, six of the eight women given CBT regained full fertility, with one showing some signs of restored ovarian function.

Two later became pregnant within two months.