Social networkers have found a new frontier for the ever-blurring line between inner and outer worlds: ultrasound photographs.

Browse through MySpace profiles or the blogosphere and you can find an expansive collection of in utero snapshots at various stages of the fetus's growth, from grainy, barely readable pictures to the much more vibrant 3D and 4D pictures that show depth and movement.

Many moms-to-be say posting ultrasound photos is an easy way to announce an exciting piece of information to lots of people all at once. But some warn that sharing fetal pictures could be oversharing — like posting drunken makeout photos — and fret about what happens if the pregnancy goes wrong.

Ultrasounds are used to examine, among other things, the health, growth and gender of a fetus. The process involves reading sound waves to create an image or video.

Moms-to-be post the prenatal shots with adoring comments like, "Here you can see the spine and little riblets," and, "Cute little foot!"

Laura Cooke, 25, from Frostburg, Md., says her blog, Facebook and MySpace pages are meant for family and friends scattered around the country, and everybody enjoyed seeing her ultrasound photos.

"My grandmother was just tickled pink," she said. "They didn't have that when she was having kids."

For Melissa Hemrich, 29, from Marysville, Wash., it was a matter of convenience more than anything else.

"When you're pregnant, everyone's excited and wants to see pictures," she says. "Everyone's going to ask you to send it anyway."

More expectant parents are sharing minute details of pregnancy over the Internet and exchanging information with family, friends and other expectant mothers. Facebook offers applications such as pregnancy tickers that allow users to post updates throughout the nine-month process.

Pregnant bloggers can join conversation groups based on their due-date month, and compare their experiences with others going through the same thing. And networking sites for new parents abound, bursting with message boards, baby shower registries, expert advice and other information about what to expect.

www.TheCradle.com, which caters to an audience of women from pre-pregnancy through their baby's first year, offers the chance for users to create their own pages, read celebrity interviews with pregnant stars and chat with other moms-to-be.

"With technology, with social networking in general, it's just creating this venue for things that everyone kind of thought was more private than it should be or than moms want it to be," says Amy Fierstein, vice president of marketing and new business development at www.TheCradle.com.

A lot of message board contributors on that site use their babies' ultrasound photos as their icon, Fierstein says.

Unlike Facebook or MySpace, where your online friends are typically people you know in real life, sites with mommy message boards often draw in users who feel anonymous enough to ask embarrassing questions or vent honestly about what they're going through.

But are there potential dangers? With ultrasound photos, there is usually personal information written on the scan.

Also, when posting such a photo or other personal images onto a social networking site, you can easily forget who will see the photo and accidentally make your news known to the wrong people, such as an ex-boyfriend who didn't know you were pregnant.

Many expectant mothers say they have taken advantage of privacy filters and other measures to make sure only designated readers can view the photos, and only certain photos.

There is also the sensitivity of the subject matter to consider. Elizabeth Bouffard, 35, of Portland, Ore., says she has a friend who jokes about how inappropriate it is to post pictures of one's uterus online.

And what if things don't go as planned? Bouffard says during the first trimester she only posted photos for friends and family to whom she knew she would feel comfortable delivering bad news, should the pregnancy not work out.

Now that she's further along and feeling more secure, she has opened up her blog and MySpace page to a wider audience.

"Getting to the point where there's an ultrasound photo, it's kind of a big deal," she said. "There's a sense of pride."

Bouffard, due in November, says she doesn't find ultrasound photos particularly private, but when it comes to photos of her daughter after she's born, it's going to be another story.

A friend of Bouffard's once noticed that a photo she had posted of her daughter coming out of a bathtub, which she had uploaded to a photo-sharing site, had gotten hundreds of hits while a photo of her daughter fully clothed got only a handful. The friend was made aware of the "creeps" one might attract by innocently sharing baby photos, Bouffard says.

But like any online presence, sharing the details of a pregnancy is a matter of personality. How open are you in the first place? How much are you willing to share with others, possibly others whom you don't even know?

Nikki Elias, 22, of Palmdale, Calif., has her 17-week ultrasound as her profile photo on Facebook and says she has nothing to hide.

In big red letters, with an arrow, she wrote, "PENIS," so that the average non-ultrasound reading viewer can know the baby's gender.

"I'm just ready to climb a mountain and scream, 'I'm having a boy!'" Elias says. She's very open about everything online, she says, and thinks it brings people closer to each other when they share their intimate trials and joys.

"It's all life," she says. "I don't understand why everything should be private."