Stress and tension will not reduce the chances of falling pregnant through IVF, experts say.
Emotional distress caused by infertility treatment, or day-to-day stress in a couple's life, will not prevent the technique from working, according to a study.
Experts said many women believe they will not get pregnant either naturally or after fertility treatment if they are stressed.
But a review of 14 studies on fertility treatment and stress found this not to be the case.
Last year, experts at Oxford University found that high stress levels may cut the chance of falling pregnant in women trying to conceive naturally.
Markers for two stress hormones, adrenalin and cortisol, were measured in saliva.
Those women with the highest levels of alpha-amylase (an indicator of adrenalin levels) had about a 12% lower chance of getting pregnant during their fertile days each month compared to those with the lowest levels of the marker.
In the latest study, experts led by Professor Jacky Boivin from the Cardiff Fertility Studies Research Group examined the effect of stress on women undergoing a single cycle of IVF or some sort of assisted reproduction.
A total of 14 studies involving 3,583 infertile women were included.
Most of the women were assessed before fertility treatment for anxiety and stress, and some during the cycle.
The results showed that women who were stressed or anxious had the same chance of falling pregnant as those who were calmer.
The authors, writing in the British Medical Journal (BMJ), said the findings "should reassure women and doctors that emotional distress caused by fertility problems or other life events co-occurring with treatment will not compromise the chance of becoming pregnant".
Clare Lewis-Jones, chief executive of the charity Infertility Network UK, said: "It is encouraging to hear that this research supports the view that stress is unlikely to impact on the success of fertility treatment, particularly as we know that the emotional impact of infertility is enormous, and often likened to that of bereavement.
"However, the authors also say research in this area is lacking and we would support the need for continued research in this important area.
"Whilst stress may not impact on the success of treatment, the need for patients to receive support and understanding should not be ignored.
"Clinics should ensure that they make every effort to care for their patients not only in terms of the best possible treatment but also to support their emotional and practical needs."