"Here are photos of me pregnant in real life so the 11 guys waiting outside my home for a (unicorn) sighting will leave me alone," she wrote. "You freak me and my kids out. Thanks to everyone else for all the love and respect and for continuing to unfollow accounts and publications who share photos of children. You have all the power against them. And thank you to the media who have a 'No Kids Policy'. You all make all the difference. Much love," she added.
Blake Lively did not announce her pregnancy. People simply found out she was expecting a fourth child because she attended the 10th Annual Forbes Power Women's Summit last week and was showing a visible bump.
The news made headlines all over the world, unsurprisingly given Lively and Reynolds' Hollywood clout, and a bunch of paparazzi took no time to camp out outside her home.
Some social media users actually blamed Lively for the paparazzi outside her house, accusing her of "wanting the attention" because why else would she have attended the Forbes event?
That was not a public announcement, that was just a pregnant woman existing, but some people's opinion was essentially that she was "asking for it".
Don't get me wrong: as one of the most privileged people in the world, Blake Lively is not exactly high on my list of people who need defending - but her children, as any children, do.
We seem to all get so hung up on the idea that these celebrities somehow owe us insights into their private lives that we forget one important point she mentions in her post: there are kids involved - kids who did not choose to be famous and who get "freaked out" by paparazzi stalking them.
This is a battle the actress and mother-of-three has been fighting for some time.
Last year, she spoke out against paparazzi following her and her children then publishing a picture of the "hands-on mum". She called the photo "deceitful" and, once again, took to social media to tell her side of the story behind the image.
"The real story is: My children were being stalked by a man all day. Jumping out. And then hiding. A stranger on the street got into words with them because it was so upsetting for her to see. When I tried to calmly approach the photographer you hired to take these pictures in order to speak to him, he would run away. And jump out again at the next block," she wrote.
"(For) the photographers who would speak to me, I was able to agree to smile and wave and let them take my picture away from my children, if they would leave my kids alone. Because it was frightening," she added.
Lively and Reynolds never announced the birth of any of their children and mostly keep them out of the spotlight.
"All that sort of stuff with kids and revealing ... I just don't feel the need to publish it," she said in a 2016 interview. "It's a normal feeling that most people might have. ... (My children) didn't really choose this profession or this life, and they can quickly get swept up in that world."
Despite remaining consistent about this across the years, and being one of many Hollywood celebrities who demand privacy for their children, Lively has found herself once again having to worry for her children, because of people camped outside looking to take photos of them.
Blake Lively's Instagram post is not a pregnancy announcement - it's an act of defiance. It tells the paparazzi that she has the power to release her own photos to the world, thus making their shots of her worthless (or at least worth a lot less).
However, she should not have to feel like she has to do that in the first place.
She posted these photos this week in order to protect her children. And while fans were happy to see her looking so happy - we'd rather she had chosen to share those photos with the world, rather than feeling like she had no other option.
As a society, we need to question why we feel a sense of entitlement to the private lives of celebrities - and we need to question even more why we feel entitled to see photos of their children.
Social media at least gives people like Lively the option to beat the paparazzi at their own game - but it’s a game she shouldn’t really have to play.
