No doubt, fans were surprised when Blac Chyna and Rob Kardashian announced on Friday that she is pregnant with their first baby.

The glamour model has a 3-year old son, King, with ex-boyfriend Tyga so this will be her second child, but with another man, Rob, which is his first. This announcement came out in less than four months after the two have disclosed that they are indeed a couple.

Blac Chyna is already in her second trimester and has informed King that he is going to be a big brother soon, according to a source close to E!

But the question is how did they keep the pregnancy secret for so long?

Perhaps there is no question as to why since everybody knows that a lot of things are affected if glamour models such as Blac become pregnant. Modeling gigs, endorsements, and shows among other things will be fewer, considerably affecting their bottom line.

Some would even abort their child just to preserve their shape so that they can get glamour modeling gigs and make more money.

But Blac is not about to do that since she is already in her second trimester, meaning she has been nurturing the fetus inside her body for a considerable time now. So, how did she and Rob keep her pregnancy under wraps?

She simply went on with her life during the first days and months of her pregnancy as if she wasn't pregnant, fooling everybody that she's her everyday normal self - as simple as that.  

In the last few months, she has been photographed in public often while wearing revealing outfits, and did not divulge any baby news whatsoever. Blac made a number of club appearances and went out on dates with Rob often.

When Blac Chyna and Rob Kardashian announced their engagement last month, they did it in a strip club. A month earlier, she was also seen during a club appearance with a glass in her hands, while sitting with friends in front of a table adorned with bottles of wine. But she didn't drink alcohol, according to E! News.