Women have fewer children if they live with their mother or mother-in-law, a major new study suggests.
Researchers found, on average, females who live just with their spouse have more children than those who share a bathroom with their relatives.
The findings dismiss widely held theories that sharing a house with a mother or mother-in-law would encourage women to have more children.
Austrian scientists made the conclusion after assessing statistics attained from 2.5 million females across the world.
Until now, biologists assumed that a woman who lives with her mother or mother in law would have more children.
But the new study, ‘dubbed interesting’ and published in the journal Royal Society Open Science, discovered the opposite effect.
Writing in the journal, the researchers said: ‘Our data thus point to lower fertility in case of the presence of any mother in the household.
‘This is interesting, as one would expect that both mothers should have “some biological interest” in a higher number of grandchildren.
Experts blamed reproductive competition behind why many women choose not to have children while living with their own mother or in law.
The University of Vienna team noted how the grandmothers tended to be younger if they were still living with their daughter, or son’s spouse.
They suggested that a younger grandmother may have children on her own which is more important than raising their own grandchildren.
This may cause a woman to avoid becoming pregnant, as they would perhaps feel they wouldn’t receive enough support with their newborn.
How was the study carried out?
Researchers used census data of 2,478,383 married women between the ages of 15 and 34 from 14 countries, including the US, Iraq and Argentina.
Analysis showed a stark cultural difference between which women tend to live with either their parents or in laws. All of the participants lived with their spouse.
Some 1.47 per cent of American women live with their husband’s mother, compared to 53 per cent in Iraq, the results revealed.
While the amount of those living with their own mother ranged from 0.79 per cent in Malawi to 17 per cent in Thailand.
The analysis bracket included all women still in their reproductive years, in theory, meaning they had yet to complete their family.
Education, where they lived and their partner’s education level were also assessed for any potential effects on the number of children.