"So, speaking of kids . . ."
Take a brief pause for dramatic effect before continuing on with whatever story it was you meant to be telling, of the sort that has nothing whatsoever to do with your having your own children personally*. Can't you just feel the marital excitement?
*Edited to Add: In my case, I was launching into a story about my friend's kid. Yes, really. Please refer to my State of the Uterus address for any additional questions.
You may want to alert your neighbors before trying this. As I recently and quite accidentally learned, you will not have time after those words slip out; if your partner is anything like the Anonymous Husband, I assure you that he will have already levitated into the next zip code. After all of the wifely hard work you've put into
ordering takeout making dinner, what a shame it would be to have to waste your evening tracking down your husband, aka Terrified Spice.