How Ashley Olsen Kept Her Pregnancy a Secret -- Even From Friends

Ashley Olsen is a new mom to a son named Otto, a source confirmed to ET.

When it comes to keeping your pregnancy out of the public eye, Ashley Olsen could teach a master class. 

The former child star-turned-fashionista was back in the headlines on Monday when it was revealed she and husband Louis Eisner had welcomed their first child together -- and reportedly months ago at that. She gave birth to a baby boy named Otto earlier this summer, a source told ET. The news was doubly surprising considering fans did not know the Row co-founder was expecting. 

According to a source, even some of Ashley's friends were out of the loop. "She kept her pregnancy secret from a lot of friends and colleagues," the source said. "Only a small circle knew."

As for how she pulled it off, the source said that the new mom's signature oversized outfits helped, as did the fact that the couple has been spending a lot of time in the Hamptons. 

Of course, some important people who did know about the pregnancy were her family, including twin sister Mary-Kate Olsen. They are all "beyond excited to have a new addition to the family," the source noted. 

Felipe Ramales / SplashNews

Keeping milestones quiet has proven to be an art form for the famous twins. In an era of sponsored content, exclusive magazine covers, and elaborate social media announcements around weddings and babies, their special occasions have continued to remain out of the spotlight over the years with the press usually learning about them after they've already happened -- and without any public affirmation from either star herself. 

While the celebrity sisters rarely talk about their personal lives, a source newly told ET, "Having a family has always been a priority for Ashley and Louis."

"Even though her upbringing was anything but typical," said the source, "she does like some of the more traditional things. For example, they wanted to be married first before starting a family."