On the Internet, a lot of companies probably know if you're pregnant. (iStock)

Facebook founder and chief executive Mark Zuckerberg and wife Priscilla Chan shared happy news Friday: The couple is expecting their first child after several years of trying and three heartbreaking miscarriages.

Of course, they announced on Facebook.

But not everyone wants news about their pregnancy online. In fact, the online advertising industry that free online services are built on can sometimes end up reminding women who suffer miscarriages of their loss.

You don't need to actually announce your pregnancy online for the Internet to find out about it. Nearly every click you make is tracked by companies that are hoping to use data about your online behavior to target advertisements. And visiting sites about parenting or looking at items like diapers or baby toys is probably enough to tip them off about your family plans.

So online advertising companies may know about your baby news before even your closest friends and family. But they may not know when to stop talking about babies if something in the pregnancy goes wrong.

"Amazon can you please stop sending me deals on baby strollers and car seats? It kind of doesn’t help that corporate America is knocking on my door with daily reminders," one miscarriage blogger wrote in 2009 post titled "Why Targeted ads SUCK."

If you want to keep your pregnancy a complete secret from the Internet, you may need to resort to extreme measures. When Princeton sociology professor Janet Vertesi tried to keep her pregnancy away from online advertisers last year, she used anonymous browsing tool Tor to look up baby information, according to Mashable.

She also made purchases in local stores with cash or online using pre-paid gift cards tied to a separate e-mail account specifically created for buying baby stuff -- and had them delivered to a local storage locker, not her home address. Basically, she started acting really suspicious.

"Those kinds of activities, when taken in the aggregate [...] are exactly the kinds of things that could tag you as likely engaging in criminal activity," she said during a panel at the Theorizing the Web Summit in April of 2014.

Of course, once she had participated in the panel, her pregnancy news became a big deal online.

“Now it’s more public than I could ever imagine,” she told Forbes at the time.