Healthy women trying for a baby may have reduced chances of becoming pregnant in any month if they are stressed, the results of a study by researchers at Oxford University and the US National Institutes of Health suggest.
The work provides evidence for the first time of an association between high levels of a biological marker for stress and reduced chances of a woman conceiving during the fertile days of her monthly cycle. The study, published in the journal Fertility and Sterility, suggests that some couples wanting to become pregnant may benefit from relaxation techniques.
'This is the first study to find that a biological measure of stress is associated with a woman's chances of becoming pregnant that month,' explains Dr Cecilia Pyper of the National Perinatal Epidemiology Unit at the University of Oxford. 'We looked at a group of healthy women aged between 18 and 40 who were all planning a pregnancy. We found that those women with high levels of a marker for stress were less likely to succeed in conceiving.
'The findings support the idea that couples should aim to stay as relaxed as they can about trying for a baby. In some people's cases, it might be relevant to look at relaxation techniques, counselling and even approaches like yoga and meditation,' Dr Pyper says.
It is well-known that age affects the ability of women to conceive, and there is evidence that smoking, obesity and alcohol consumption can affect the likelihood of becoming pregnant. As a result the advice given to women planning to get pregnant includes stopping smoking, eating a healthy diet, lowering alcohol intake and taking folic acid.
Stress has also been suggested as a factor affecting the chances of couples conceiving, but this has been based largely on anecdotal or indirect evidence. So the research team from Oxford University and the Eunice Kennedy Shriver National Institute for Child Health and Human Development set out to measure stress levels among healthy women seeking to get pregnant and see whether the levels were related to their chances of conceiving.
'We want to understand the things that affect the chances of pregnancy for normal, healthy women trying for a baby,' says Dr Pyper. 'Many couples are very keen to know what they should do to improve their chances of conceiving and having a healthy baby, and this will help us provide the best advice.'
The study included data from 274 healthy women aged between 18 and 40 who were trying to become pregnant. During the study, the women provided saliva samples on day 6 of each of their menstrual cycles to test for levels of the hormone cortisol and alpha-amylase (an indicator of adrenalin levels).
The body has two pathways that respond to stress: one involves the release of adrenalin and the other the release of cortisol. The adrenalin pathway is associated with the body's instant 'fight or flight' reflex. Cortisol is connected with longer periods of raised response and stress.
The results showed that the chances of getting pregnant for the quarter of women in the study with the highest levels of alpha-amylase were roughly 12% lower than the quarter of women with the lowest levels of alpha-amylase, each day during the fertile days of their menstrual cycle.
No differences in the chances of becoming pregnant were found for women with different levels of cortisol.
This is the first time any study has seen a difference in chances of pregnancy associated with a biological measure of stress. Although the study has provided evidence of such an association for the first time, a larger study would be necessary to determine the size of this effect, or measure any time delay in women succeeding in becoming pregnant caused by higher stress levels.
'While these novel findings suggest a possible negative effect of stress on conception probabilities during the fertile window, we still don't know if delays in conceiving will raise women's stress levels and further reduce their chances of conceiving,' explains Dr Germaine Buck Louis of the Eunice Kennedy Shriver National Institute of Child Health and Human Development and corresponding author of the study.
'More work is required to understand the size of the effect of stress on the chances of becoming pregnant and how it compares to the effects of factors like smoking, obesity and alcohol,' says Dr Pyper of Oxford University. 'Further studies would also be needed to determine whether relaxation and stress-reduction techniques could have beneficial effects and improve couples' chances of conceiving.'
The women who took part in this study were participants in the bigger Oxford Conception Study led by Dr Pyper. This large study has recruited 1500 healthy women in the UK trying to become pregnant and aims to see whether a fertility monitor could help them. It is also looking for the effect of factors like smoking, alcohol and caffeine on chances of pregnancy.
The study was funded by the Intramural Research Program of the US Eunice Kennedy Shriver National Institute of Child Health and Human Development, the UK National Health Service and the DLM Charitable Trust. Unipath Corporation provided fertility monitors and pregnancy tests used in the study.
- Buck Louis et al. Stress reduces conception probabilities across the fertile window: evidence in support of relaxation. Fertility and Sterility, 2010; DOI: 10.1016/j.fertnstert.2010.06.078
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