Many people will spend Mother's Day, this Sunday (May 11), celebrating the love, warmth and emotional support they get from their mothers.
But did you know that many moms are also genetic mutants whose very brains altered in the process of motherhood? Yes, this makes good old mom sound a little bit like an X-man, but there's science behind it, we promise.
So this Mother's Day, we've rounded up some of the stranger scientific facts about motherhood. Read on, and then go give that sweet mutant mom a hug. [7 Ways Pregnant Women Affect Babies]
1. Mom's a genetic patchwork
Pregnancy changes the body, but stretch marks get all the glory. A much cooler side-effect of gestation is that moms may carry little pieces of their children with them for years to come.
It's called microchimerism. The placenta separates the blood flow of mom and baby, but a handful of fetal cells cross this barrier and lodge in mom's body. Scientists have found that these cells can persist for years or even decades. The role of these cells, if any, remains mysterious. But a 2012 study found that DNA from a child's cells could even end up in mom's brain.
2. You changed her brain
Research in rodents has found that having offspring changes the brain. When pregnant mom-to-be rats gain new smell-related neurons — perhaps the better to recognize her babies' scent with. These changes persist throughout the mom's life, according to a 2011 study.
The human brain is not immune from pregnancy-related change, either. A yet-unpublished study presented on May 7 at the annual conference of the British Psychological Society found that pregnant women use the right side of their brain more than new moms when looking at images of adult and baby faces sporting different emotions. The effect was strongest when pregnant women were processing happy faces, the researchers reported. The changes may be part of promoting the mother-baby bond after birth, they suggested.
Previous studies have found that pregnant women and new moms get a boost in their ability to read facial emotions, and these brain changes may be related.
3. She might help your love life
The pushy mother-in-law is a time-honored stereotype, but cut mom a break. She may have done more for your love life than you think.
A close and warm relationship with mom during childhood predicts better relationships later in life, according to research presented at the 2010 annual meeting of the Association for Psychological Science. Maternal help in the romance department may even cross species lines: Another 2010 study, this one published in the journal Nature Communications, found that low-ranking male bonobos get more chances to mate when mom is around. Moms play matchmaker by allowing their sons into their social circles, and even chase away rival males.
Not feeling lovey-dovey? Good news: A strong bond with mom can help kids make friends, too.
4. You might have made her a little OCD
If your mom seems to worry a lot, you may not be imagining things. Having a baby makes people a bit obsessive, it turns out.
Northwestern University researchers studied new moms when their babies were 2 weeks and 6 months old, and found that 11 percent had significant symptoms of obsessive-compulsive disorder, such as fear of germs or compulsions to check and recheck the baby monitor. In comparison, only about 2 percent to 3 percent of the general population has these symptoms, the researchers reported in 2013 in The Journal of Reproductive Medicine.
When taken to an extreme, these symptoms can be harmful, the researchers wrote. But some worries are probably normal and adaptive — taking care of a newborn is tough work, after all. The increase in obsessive symptoms may be a result of stress or postpartum hormones.
5. Her voice is powerful
You knew your mother's voice before you were even born. A 2003 study out of Queen's University in Canada published in the journal Psychological Science found that the fetal heart races faster when hearing a recorded poem read by its own mother compared to when the poem is read by a stranger's voice. The study was conducted in the third trimester, when babies were nearly ready to be born. [That's Incredible! 9 Brainy Baby Abilities]
Another study from the University of Montreal found that the newborn brain is as responsive as the fetal heart. When moms made a short "A" sound, the left hemisphere of brand-new babies' brains became active, while the right hemisphere became active when a stranger spoke, the researchers reported in 2010 in the journal Cerebral Cortex. The right hemisphere of the brain is linked to voice recognition, while the left processes language and motor skills, so mom's voice may lay the groundwork for a baby's first words.
This vocal maternal superpower continues long past the baby stage. Hearing a mother's voice eases older children's stress just as much as a real-life hug, according to a 2010 study. The sound of mom's voice lowers a child's stress hormone, cortisol, and raises his or her level of oxytocin, a hormone linked with love and bonding. So give your mom a call this Mother's Day. It'll do you both good.
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Stephanie Pappas is a contributing writer for Live Science, covering topics ranging from geoscience to archaeology to the human brain and behavior. She was previously a senior writer for Live Science but is now a freelancer based in Denver, Colorado, and regularly contributes to Scientific American and The Monitor, the monthly magazine of the American Psychological Association. Stephanie received a bachelor's degree in psychology from the University of South Carolina and a graduate certificate in science communication from the University of California, Santa Cruz.