Did she (spoilers)
Know she was pregnant the whole time?
My theory is that she found out she was pregnant and that triggered a mental breakdown where most of the film is hallucinations/her mind warping reality.
I'm just putting this out there because at the start of the film she has brown eyes but by the end her eyes are blue. HOWEVER when she's getting the ultrasound and realises she's expecting twins her eyes are brown.
So did she know and was the whole film about her deep denial since she kept asking why is was happening now, did she know deep down and was she just too scared to deal with the unplanned pregnancy?