Spoiler alert

Rating: 10/10 (9 October 2019)

First things first: this movie is nÂ° 2 on my all time favourite sci-fi movies. Ever. Arrival is a very complicated never incoherent movie with low to zero action. God bless it.
Besides Adams' brilliant performance the whole movie is well balanced and never boring, smart at the point that forces you to think into it not just for a little more of the 2 hours needed to watch the movie.
I've read comments about time implication like "hurr if alienz knewz teh future how come they couldn't think about a proper solution duh".
I would love to shortly answer to this: first of all we have no idea of what the problem they'll need us to solve will be, so we have litterally no hint about if thr problem itself could ever be solved by aliens alone. Second of all the movie stands by the concept of a unique timeline so they knew both this story would've gone this way and that they would have behaved exactly like how they foresaw, because that's the huge implication over there. Given this info it comes naturally that she had no choice in having a baby with Ian because that is how timeline works in this story. Does timeline work like this in our universe? Well the question is far away from being solved but for sure this movie gives a great and mind blowing answer to this.