By Caroline Ryan
BBC News, Prague
Counselling helps "perfectionist" women regain their fertility and become pregnant, US researchers say.
Stress can damage fertility
They found cognitive behaviour therapy alone was enough to help some women who had stopped having periods and ovulating to regain their fertility.
The therapy is usually used to treat people with depression.
A European fertility conference in Prague heard a build-up of stress can play a major role in preventing a woman from ovulating.
But sometimes the effect can build up gradually in a subtle way.
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.
Others felt overwhelmed and stressed by the demands they felt they had in their lives.
However, none had been diagnosed with anxiety or depression.
The researchers, from Emory University in Atlanta, Georgia, have been investigating why these women, who are otherwise healthy, stop having periods or ovulating for over 20 years.
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.
They had all been diagnosed with a condition called functional hypothalamic amennhorea (FHA), caused by a prolonged reduction in levels of a hormone which signals the release into the bloodstream of hormones that simulate ovulation.
The women had been shown to have increased levels of cortisol, a hormone linked to stress.
Half were given cognitive behavioural therapy, tailored to their own situations for 20 weeks.
This was designed to provide them with advice on how they could deal with their problems and keep them in perspective.
The rest of the women were simply observed.
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.
In the eight women who received no treatment, one recovered her fertility while another showed signs of ovarian function.
Women in the CBT group saw cortisol levels fall and a restoration of a key signal which prompts ovulation.
Lead researcher Professor Sarah Berga said medics should not simply return to the days where women were simply told 'relax and you will get pregnant'.
"People do not relax just because you have told them to. You need to teach them how to relax.
"These are subtle effects we are seeing. What we need to do is help women to cope and help them not to make mole-hills out of mountains."
She added: "CBT should be provided by the state, as it's cost-effective and much cheaper than funding fertility treatment."
The team now to study up to 4,000 nurses to monitor their menstrual cycles and see how stress and reproductive hormones change, so that they can evaluate the true extent of the problem.
Dr Mark Hamilton, chairman of the British Fertility Society, said: "About 20% of women who are infertile have problems with ovulation.
"Many of those are related to weight, but a number do have problems with ovulatory function.
"We know that lifestyle factors can influence the menstrual cycle, so it's appropriate that medical practice takes account of that, and CBT is one approach that could be helpful."