Stressed women are more likely to give birth to a girl than a boy, new research has suggested.
A study published in the journal of the Proceedings of the National Academy of Sciences (PNAS) indicated that mums-to-be who feel overwhelmed or depressed are less likely to have a boy.
In order to determine how maternal stress levels could potentially impact gender, the team at Columbia University in New York analysed different indicators of stress from a series of questionnaires, diaries, and daily physical assessments of 187 healthy pregnant women.
They found that 17% of the women were psychologically stressed, characterised by high levels of depression and anxiety. Another 16% of women were physically stressed, indicated by higher daily blood pressure and greater caloric intake.
This group of women, that were either psychologically or physically stressed, ended up giving birth to more girls than boys.
On average, around 105 males are born for every 100 female births. But in this study, the sex ratio in the physically and psychologically stressed groups favoured girls, with male-to-female ratios of 4:9 for those who were physically stressed, and 2:3 in women who were psychologically stressed.
After the results, the scientists proposed that pregnant women who experience physical or psychological stress might be less likely to have a baby boy.
The researchers believe the phenomenon may be explained by the fact male foetuses take longer to complete their early developmental stages, leaving them more vulnerable to sub-optimal conditions in the womb.
"Other researchers have seen this pattern after social upheavals, such as the 9/11 terrorist attacks in New York City, after which the relative number of male births decreased," leader of the study Professor Catherine Monk said.
"This stress in women is likely of long-standing nature; studies have shown that males are more vulnerable to adverse prenatal environments, suggesting that highly-stressed women may be less likely to give birth to a male due to the loss of prior male pregnancies, often without even knowing they were pregnant."
Professor Monk said the study was not meant to “alarm women or blame them”, but just to encourage women to seek help and support if they are feeling stressed or overwhelmed.
“It’s an important opportunity to find ways to manage your stress, whether it’s meditation, time with family, friends, religion or knitting,” she added.
So, if you're trying to conceive, looking after your mental health could help lead to a safer pregnancy and could even increase your likelihood of having a boy.
Professor Monk said: "What's clear from our study is that maternal mental health matters, not only for the mother but also for her future child."
It’s worth remembering, however, that even if you’re feeling stressed during pregnancy your unborn baby is unlikely to be harmed.
“Remember that our bodies are designed to cope with stress, so there's no need to worry if things do get on top of you every once in a while,” community midwife, Clare Herbert told Babycentre.
“Even so, it does make sense to try to minimise any pressures you might be under. If nothing else, it’ll help you to enjoy your pregnancy.”
Any woman concerned about the impact stress could be having on their pregnancy should see their doctor or midwife.
Earlier this year researchers discovered a link between an expectant couple’s emotional state before and after their baby is born - and the child’s own behaviour during their early years.
Research that analysed 438 first-time parents, and was published in the journal ‘Development and Psychopathology’, found that mums who suffered from prenatal stress and anxiety while pregnant were more likely to see their child experience temper tantrums, restlessness and spitefulness.
And last month a further study found that women who experience stress during pregnancy could be more likely to have children with personality disorders.