Women who are stressed out when undergoing IVF may have a higher chance of falling pregnant, research suggests.
Those reporting higher stress levels had up to double the chance of a positive pregnancy test when compared with those who were more relaxed, according to a study on 217 women.
They were asked on their first appointment how much fertility-related stress they were experiencing on a scale from 1 to 10.
Those who scored 1 to 3 on the scale had a pregnancy rate of 30 per cent while those who scored 7 to 10 had a rate of 50 to 60 per cent.
Dr Robert Hunter, from Staten Island University Hospital in New York, which carried out the study, said previous research had found a similar finding. However, other studies have discovered that stress can negatively affect IVF.
'We were a little surprised by the outcome of the study - we were expecting the opposite result,' Dr Hunter said.
'It highlights the complexity of stress. There's a very complex relationship between stress pathways and the reproductive pathways.
'This is something that we're still struggling to understand and more work needs to be done.'
Dr Hunter said there was good evidence, however, that stress could actually improve how the body functions, such as the 'fight or flight' response.
Levels of key hormones rise when a person is under stress, including the adrenal hormones adrenaline and cortisol.
The team are now planning further studies, including looking at these markers of stress in the body.
Co-researcher Dr Eric Knochenhauer said questions also need to be asked about sources of stress, such as coming from a partner, worries about the costs of IVF and pressure from parents, in-laws or friends.
'Fertility-related discussions used to be something that nobody had with friends but now it's much more common,' he said.
'I think that causes stress for some patients.'
Another one of the researchers, Dr Michael Traub, said one interesting finding from the study related to older women, who reported being less stressed.
'If they are older and they think their chances of becoming a parent are very low, they might have less stress because their expectations are lower.'
All the findings held true even when factors such as depression, smoking status, age and alcohol intake were taken into account.
Tony Rutherford, chair of the British Fertility Society, said: 'This study used a questionnaire to assess stress rather than looking for biochemical markers.
'There is some evidence that increasing stress might be of benefit to patients undergoing IVF.
'In the UK we are pushing for a national trial on whether steroids improve IVF.
'It's an interesting relationship.'
