It has driven me crazy about this movie that nobody seems to have figured out what is going on at the end and thinks its so mysterious. Come on! The girl who was so into drinking whiskey with her parents refuses a drink. Her mom tells her she's glowing. She'd been with another man in England. So at the end when she's reunited with her husband and they're in the shower, he sees or feels that she is pregnant by someone else.
share*it's so mysterious
shareSimon is clearly a fitness freak. I think the point of that scene was more to show that he's influencing and changing her (going so far as 'simon says'), in a way that Jacob didn't. It makes perfect sense without having to add the pregnancy theory into it.
As for glowing, the mother herself says that she thought it was just the promotion (as opposed to the health business above). So there's two perfectly valid explanations for her glowiness explicitly handed to us.
I think you can read pregnancy into it, but there simply isn't enough data, or any mystery needing explaining.
Also I think the film is just way too focused on their emotions and internal struggles to just end on such a dorky melodramatic contrivance.