I'd give this 4 stars because I found the topic important and appreciated the approach and the theme, but some parts were unsettling. I wished the storytelling was also more cohesive.
However, it's frightening since the female lead experienced the unspoken emotional turmoil of motherhood. They used suspense and thriller elements to bring to life what postpartum depression might feel like and that's what makes the film scary for me, as it can happen to any woman out there. It's an unsettling reality where one's sense of self starts to fragment.
I agree with the other comments – what I mentioned above might be the underlying movie theme (postpartum). At least, that's what I picked up when I watched it. I hope this comment helps. It's worth watching, I guess as it raises awareness of what mothers go through after giving birth, and the people around them.