Rarity: Hnnnngg.... Spiiiiiike my perfect figure is gone and I simply can't stop eating! It's absolutely awful!
Spike: Ehehe, it's alright you still look amazing to me.
Rarity: Oh please don't even go there. I know you're just saying that.
Spike: N-no I'm not!
Rarity: Yes you are!
Spike: Fine, so what do you want me to say? Gee Rarity you sure have been looking pretty pudgy lately
Rarity: How could you say that Spike D:
Spike: I just can't win can I?
As a two-time father, I can say that variations of that complement worked both times. At the very least they lifted her mood, because she tended to get depressed when she had cravings. I understand it's different for every woman.
* If you subscribe to the idea that Ki-rin (equine-dragon hybrids) come from an egg, Rarity is in that case incubating their baby's egg. Either way, the complement still holds.
Today I learned that pregnant women get constant moodswings. Rarity is having constant bouts of freaking out and sharp tongued moments. The test of a father is to care for the mother-to-be, keeping her happy and comfortable. This is going to be a long nine months or so. Aren't you glad I was adopted?
Your son Spike