There is something absurd about a pre-pubertal girl wearing thong underwear—but I see it all the time. After almost ten years of practice as a pediatrician, I’ve witnessed a decade of kids’ underwear trends and styles. Sexy underwear are appearing on younger and younger girls, from Victoria’s secret satin, to thong, to fluorescent string bikinis. Their child-like, curve-less hips aren’t made for sexy underwear. So why do moms let their daughters wear adult-styled underwear?

I’ve heard all the arguments:

“Thong underwear are for preventing panty lines—they are functional, not meant to be sexy.”

“Pretty underwear help girls feel good about themselves. They’re important for self-esteem.”

“She has to change for PE, and everyone sees her underwear. She doesn’t want to wear regular cotton underwear anymore.”

“Shopping at Victoria’s secret with my kids is a great time to talk about why sex is a normal, healthy thing.”

Cherish Childhood

Here’s what I think: childhood is getting shorter—our daughters are growing up too soon. Our daughters are trying to look like grown-ups before they have grown-up bodies. Tweens wearing sexy underwear is just another example of all the other adult trends that have worked their way into childhood. According to the American Society of Plastic Surgeons, More than 326,000 18-and-unders had plastic surgery procedures in 2004 to correct something that made them self-conscious. Kids as young as 10 and 12 go to tanning salons, in many states without parental permission. One woman in New Jersey was arrested for bringing her six year old into a tanning device with her. And clothing styles for girls over seven look more like ladies clothes than kid’s clothes. Most moms I know struggle to find summer clothes for their daughters that cover their thighs.

Eventually, moms just want their daughters to fit in and feel attractive. A girlish appearance just doesn’t seem right for a ten-year-old anymore.

Tweens and teens not only want to look like adults, they want to act like adults, too. They are spending more time on the uncensored internet, and a growing number have their own smart phones and tablets. According to the Pew Research Center, 37% of American youth ages 12-17 now have a smartphone, up from 23% in 2011. Close to one in four teens has a tablet device. Tweens who aren’t allowed to watch “R” rated movies or play “Mature” or “Teen” rated video games feel left out and start begging their parents for these privileges. What’s the difference between the uncensored internet and mature movies and video games, anyway?

Our kids’ bodies and brains aren’t keeping up with our culture. Just as child-like hips are not ready for sexy underwear, tween brains aren’t ready for uncensored media. The adolescent brain continues to physically change and mature until the early 20’s. Tweens don’t have adult decision making skills, social skills, and self-control. We can talk to our kids about sex early and open their eyes to the world while they still live under our roof, but we can’t make their bodies mature faster.

For me, the worst part is the distraught look on the dads’ faces when they see their tween’s sexy underwear peaking out from the back of their hospital gown. Dads know—their daughters are still too young for this.