Chronic stress could harm a woman’s fertility by reducing the number of eggs in her ovaries, a study has suggested.
Chinese researchers made female rats listen to six hours of screaming every day for three weeks to mimic stress, while others listened to either white noise or background sounds.
Rats who were screamed at had significantly fewer pups on average for at least two litters after the experiment.
Scientists blamed the decline on lower levels of the hormones estrogen — which is involved in the menstrual cycle — and Anti-Mullerian, which is involved with fertility cells in the ovaries.
It is well established that stress can affect fertility in women by inhibiting the release of key hormone, which in some cases leads to periods stopping.
Men can also face reduced fertility due to stress, as it may lead to a reduction in testosterone levels which could lower sperm counts.
The above graph shows the number of pups produced in the first and second litters among female rats who were exposed to screams (green), white noise (red) or background noise (yellow). Scientists said there was a significant drop in the group exposed to screams
How could stress cause infertility?
Chronic stress is known to trigger a loss of fertility.
Doctors say it can trigger functional hypothalamic amenorrhea (FHA) in women, where they stop getting their periods because of an imbalance in hormones.
The condition can also be brough on by excessive exercise, weight gain, or an eating disorder such as anorexia.
Stress can also decrease fertility in men, doctors say, as it can reduce testosterone levels leading to a lower sperm count.
In the study — published today in the journal Endocrinology — scientists at Xi’an Jiao Tong University in Northern China looked at the impact of stress on about 100 female rats.
They exposed a third of them to a recording of screams from one of the researchers for three hours in the morning and evening every day.
Another third listened to white noise — sound from all frequencies — at the same time, while the last group heard just background noise.
After 21 days, some of the rats were euthanized to examine their ovaries and hormone levels.
The rest were placed with male rats a day after and 24 days after the experiment.
Rats in the scream group had about nine pups on average in their first litter and eight in the second.
For comparison, those in the white noise group had 13 pups in the first and 11.8 in the second.
While rats that heard just background noise had 13.9 and 12.4 pups in each.
The scientists said the number of pups in the scream group was significantly lower than in the others.
This drop was likely down to the reduction in hormone levels triggered by stress, they suggested.
Studies on the ovaries also showed there were more damaged cells in the scream group, further inhibiting their litter size.
‘Based on these findings, we suggest stress may be associated with a diminished ovarian reserve,’ Dr Wenyan Xi, a fertility expert who led the study, said in a statement.
‘It is important to determine an association between chronic stress and ovarian reserve because doing so may expand our appreciation of the limitations of current clinical interventions and provide valuable insight into the cause of diminished ovarian reserve.’