This study will come as no surprise to mums and mum-to-be.
Science boffins at Duke University have revealed that pregnancy is one of the most extreme things a human body can go through.
The study, which was published in Science Advances this month, was looking at the limits of human endurance.
It found that carrying a baby for nine months was harder on the body than mile Race Across the U.S.A., in which competitors ran six marathons a week over 120 days.
The study looked at the resting metabolic rate of activities and the human body can't endure more than 2.5 times this rate without eventually breaking down and dying.
Study co-author Herman Pontzer said, ''Every mother who has gone through pregnancy has experienced that effort themselves.''
He continued, ''Pregnancy is the longest duration, highest energy expenditure thing that humans can do. Mothers probably aren’t surprised by this.”
Scientific research concludes that pregnancy outstrips any other endurance sport. ‘No shit’ declare millions of women— Rebekah Paczek (@bekspaczek) June 7, 2019
The researchers think that nine months is the limit in terms of time that women's bodies can withstand pregnancy - and that's why pregnancy doesn't go beyond nine months and pregnant women don't go beyond a certain size.
Pontzer said, ''Human mothers have the biggest children and the longest pregnancies of all apes.''
He continued, ''While events like marathons can raise your basal metabolic rate to much higher than 2.5, it can’t stay there for long without causing health problems, and without your body calling for rest.''
Congrats Mothers! The body treats pregnancy like an extreme sport. The key is the metabolic rate, researchers found, which adapts to the level of exertion in both endurance athletes and expectant mothers. Pregnancy, it turns out, is one of the most awesome feats of humanity.— Ken Burbary (@kenburbary) June 9, 2019
He added, ''The amazing thing about pregnancy is that moms never get a rest - they are performing at an elevated level 24 hours a day, seven days a week until the baby is born. All of the limits of our endurance, whether we’re trekking across to the South Pole or building a kid - are all governed by the same machinery.''
So pregnant women, if you didn't need an excuse before - make a cuppa and put our feet up...you deserve it.