When Danielle and Jon Murray of Raleigh, N.C., learned they were having their first child five years ago, they were too embarrassed to tell their friends and family.

“To be honest, we were not married at the time,” Ms. Murray said. “And coming from Christian families and with Jon working at a church, it was kind of a taboo thing.”

When she became pregnant with their second child, the couple, by then married, hosted a gender-reveal party. With their third child, they posted a photo on Facebook.

But when she got pregnant for a fourth time last year, Mr. Murray, a videographer, wrote a parody of the electronic hit “Shut Up and Dance” by Walk the Moon and filmed a three-and-a-half-minute video.

Called “We’re Having One More Baby,” the video shows the telegenic couple bouncing around their home with their daughters while Ms. Murray waves the sonogram. “Yes, we know how it happens,” goes one line. “We just like having kids!”

To date, the video has garnered nearly 1.8 million views.

Consider the modern couple who have just learned they’re having a baby. How should they inform their friends and family? Write a note? So 1950s. Place a call? So 1970s. Send a mass email? So 1990s.

These days, when couples want to let their loved ones know they’re having a child, they often whip out their cellphones, shoot a video and post it on social media. Couples are putting their babies’ names in lights even before their babies have names.

Pregnancy announcement videos have become so popular they’re becoming businesses all their own, with YouTube compilations, Pinterest pages and morning television segments.

Even celebrities are getting into the game. Alanis Morissette, Michael Bublé and his wife, Luisana Lopilato, and Ivanka Trump all announced their latest pregnancies via video. In May, Janet Jackson revealed she’s pregnant at age 49 in a video. That same month, a zoo in Australia released a video to report that one of its elephants is having a calf.

Given this exploding form, a little deconstruction may be helpful. Herewith a guide to five popular styles.

Surprise!

By far the most common form of announcement videos involves startling unsuspecting future grandparents. Wannabe grannies, it seems, have a tendency to scream, shout, jiggle and whoop.

Daniel Woods is a wedding videographer in Johnstown, Ohio. When his wife, Ciera, got pregnant, he asked unwitting family members to sit for an interview.

“I used various excuses,” Mr. Woods said. “I told Ciera’s parents it was an anniversary video. I told my parents I needed to do a color correction.”

With the camera rolling, Mr. Woods stepped forward with his clapper and announced, “Ciera’s pregnant. Take one.” He gave his in-laws a sign that read “Grandparents Starting in April 2016.”

The slow-motion reactions of all 25 people (and the couple’s dog), which involved bulging eyes, forehead slaps, thumbs up and cheers, all set to the tune of “I’ve Been Waiting for This,” is like the Steven Spielberg of pregnancy announcement videos. It’s impossible to watch without tearing up.

Mr. Woods said, “We wanted there to be something our kid could look at and say, ‘This is how everyone reacted.’”

Movie Trailers

What says ‘coming attraction’ more than a coming attraction video? One couple filmed their pregnancy announcement as a tease for a thriller called “The Baby.”

Judy and Gavin Holt made a trailer in the style of a horror movie.

The plot, “based on a true story,” opens with a kissing couple in front of their home in California. But soon poltergeists invade, the cats starting freaking out and doors automatically open and close. A voice-over from Ms. Holt intones, “I can feel it growing inside of me.”

After going viral on Reddit, the video has been viewed almost one million times. The only pushback: Ms. Holt’s mother was upset that scaring her pregnant daughter would harm the unborn baby.

I Want My MTV

Parody music videos are popular for pregnancy announcements just as they’re popular with so much else on the web. Examples include knockoffs of Miley Cyrus, Bruno Mars and Taylor Swift.

Mr. Murray, who shoots videos for the Assembly of God church where he works, warned that while music videos are catchy, they also present a particular challenge.

“I see all these parodies that just don’t sound good,” he said. In “We’re Having One More Baby,” he and his wife recorded the lyrics on a studio mike, then lip-synced during the shoot.

“At that point it was just matching up the audio,” he said.

Here Comes Santa Claus

Christmas morning is a frequent setting for pregnancy unveilings. One couple gave the future grandparents a giant box with pink and blue balloons. As the soon-to-be grandma shrieked: “Oh, my God. You’re having a baby!” the camera rolled.

Caryn and Bryan Canatella of Austin, Tex., went even further. Mr. Canatella volunteered to scan his mother-in-law’s old family photographs for Christmas.

The couple then gathered her extended family, still dressed in holiday pajamas, to screen the compilation. Unbeknown to all, the video ended with a tease, “And then there’s more,” followed by the audio of a heartbeat and a picture of Ms. Canatella’s sonogram.

The video Mr. Canatella shot of the family’s reaction includes an inset of what they were watching on the screen. Part of the pleasure is observing as each family member figures out the message, culminating with Grandma, who hastily pushes Ms. Canatella’s bewildered nephew off her lap and leaps into the air.

The video has been viewed three-quarters of a million times on YouTube.

One Stripe or Two?

Not all pregnancy announcement videos focus on the happy moment of revelation. The current vogue extends all the way to the moment of discovery. An entire subspecies involves filming the pregnancy test — or at least the reading of the test.

One couple, Matt and April Fetch of Los Angeles, chronicled their five-year fertility struggle on YouTube, including a number of negative tests. In one video, Ms. Fetch displays her sad texts to her husband, then addresses the camera.

Her “natural intercourse cycle” has not worked, she says holding the pregnancy test tube. Then she breaks down in tears. “I don’t know why, but all of a sudden out of nowhere I’m getting very emotional,” she says.

Almost two years later, the couple posted another video. It opens with Ms. Fetch sitting in a parking lot describing her anxiety before going to the doctor for a blood test. It ends with the couple nervously listening to a voice mail message at home. A nurse reports their result is “positive.”

For the next four minutes the couple weeps, hugs and shares the moment with their 54,000 viewers.

So what’s going on here? Why this sudden interest in pregnancy announcements?

In many ways, it’s not that complicated. For as long as humans have shared stories, those stories have focused on moments of beginnings and endings — births, deaths, marriages, graduations.

What’s new is that we have the means of documentation in our pockets at all times and the means of distribution at our fingertips just as quickly. The only innovation in pregnancy announcement videos is the video part.

But what impact that has. The most popular video I watched is also the shortest and simplest. It is one shot and lasts one minute. It also came with this description: “After 4 miscarriages and 1 stillborn birth, we had given up on the idea of having babies of our own, especially at our age.”

The shooter, Dana Griffin-Graves, is holding the camera, while her husband, Arkell Graves, is preparing dinner. “There’s something in the oven, too,” she says.

He opens the door to find a bag of buns and two images of a sonogram.

He quickly pivots and stares at the camera, hopeful. “You’re pregnant? You’re pregnant. You’re pregnant!”

“Nineteen weeks. Almost five months. It’s a boy.”

The man covers his face with his shirt and sobs like the baby he soon will have.

When their son, Kaleb Arkell Graves, was later born prematurely, at 24 weeks, the couple chronicled the experience on social media.

What began as a private moment has become a community. The Graveses have a YouTube channel; a hashtag, #TeamKaleb; a GoFundMe account; a Facebook page with over 150,000 likes; and a video that has been viewed more than 10 million times.

In the booming world of everyday cinema, “Buns in the Oven” just may be the first blockbuster.