Super-strong bones, healing blood and different brains: How motherhood changes bodies forever

Women's brains, blood, hormones and bones change drastically during pregnancy, research suggests.

We are only just discovering the full extent of what is going on with women's bodies during pregnancy and beyond after decades of only studying male bodies, say scientists.

Bones

Biologists have revealed that a new hormone protects bone density during breast-feeding.

The new research, which studied mice, solves a long-standing puzzle over how the bones of breastfeeding women stay strong even as they lose calcium to milk, say researchers at the University of California San Francisco and UC Davis.

The hormone, CCN3, works by blocking certain oestrogen receptors in the brain and leads to "huge increases in bone mass", according to Professor Holly Ingram.

CCN3 even healed elderly bones faster when it was applied as a patch, suggesting the hormone could help with diseases like osteoporosis which women are particularly at risk of after menopause.

Professor Ingram added: "One of the remarkable things about these findings is that if we hadn't been studying female mice, we could have completely missed out on this finding.

"It underscores just how important it is to look at both male and female animals across the lifespan to get a full understanding of biology."

Elsewhere in the body, "powerful" changes in women's brains and healing power in mothers' blood are being revealed.

Brains

A woman's brain drastically changes shape during pregnancy, and never fully goes back to the way it was before, multiple studies have discovered.

The changes in a woman's brain are so significant researchers recently found they could correctly tell if a woman was pregnant 100% of the time, just by looking at the shape of her brain.

Dr Susana Carmona, who led the research, said the changes in a woman's brain during pregnancy "are the most powerful changes I have seen in my whole neuroscience career". She previously studied brain changes during schizophrenic episodes and people with ADHD and OCD.

During pregnancy, the brain is altering itself to prepare for parenthood, a process triggered by hormones which activate an instinct to focus almost completely on the baby, says Dr Carmona.

"You think, 'This [baby] is super interesting, I'm going to try to interact with this' and then you learn all the maternal behaviours," she said.

Some parts of the brain associated with socialising and self-perception become smaller and thinner, and are slower to bounce back after giving birth.

Blood

As well as drastically changing their mothers' brains, babies also change their mothers' blood - forever.

By the time she is six weeks pregnant, an expectant mother will have her child's blood cells running through her veins, according to Dr Diana Bianchi who first observed the phenomenon in 1996.

Back then, she found that women who had given birth to boys up to 27 years earlier still had their sons' cells circulating in their blood.

Scientists are now discovering those cells all across the body, with a recent study from University of Jaen, Spain, confirming the cells were present in mothers' hearts.

They've also been observed in areas that need healing like a diseased organ or scar tissue, suggesting the cells could help the healing process in mothers and their children long after they've left the womb.

Even if a woman miscarries, she still carries her child's blood with her for years.

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Studying women's bodies

The vast changes an expectant mother goes through are still being discovered, and extend to the entire body.

Dr Carmona blames the fact we know so little about pregnant bodies on old scientific methods.

"Until very recently, studies performed on animals only included males because they thought that controlling for the menstrual cycle was too complicated," she said.

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In fact, researcher Emily Jacobs from UC Santa Barbara found that of the 43,000 studies in neuroimaging during the last 25 years, only 0.5% study how women's brains are impacted by things like pregnancy, menopause and hormonal contraceptives.