having someone point out that "lose the baby weight" might be a problematic theme for someone with body image issues might get her to change the theme.
"Lose the baby weight" is a problematic theme WITHOUT body issues!!!
I was not really overweight before I got pregnant. I mean, technically I was (according to the scale), but I was also quite muscular and sturdy. At 160lbs, I wore a US size 7. I was healthy and robust and man, did I have great legs.
I am now over 200lbs. I feel like a cow...or maybe a small hippopotamus. I am bloated and swollen and my feet are 2 sizes bigger than normal. I feel gross and huge. My arms are flabby and my legs have cellulite that did not exist 7 months ago. I have stretch marks all over my stomach and hips, and I have been promised by friends who have previously had children that my body will never look the same again (but also reassured that it's okay).
I never really had body image issues before. Showing up at a weight-loss themed party in my honour would send me home in tears.
And I'm just your average pregnant woman.
Most pregnant women feel pretty gross by the time they are near the end of their pregnancy. You hardly recognize yourself. For most women, they don't feel particularly "magical", although we are reassured that this is a magical and wonderful experience. We rely on the reassurances of our friends and partners to be reminded that we're still beautiful.
Aside from the obviously huge etiquette breach of her partner throwing the baby shower, having her partner throw a weight-loss themed party is a terrifically bad idea. I cannot imagine it ending well.