1. Evasively
I think you have to be a certain type of person to pull off an evasive answer. I'm pretty straightforward and honest in life, so if I dodge a question, it's pretty obvious I'm hiding something, which my poker face shows. But one of my good friends who was doing IVF has a knack for changing the subject and just not answering any questions. One of her best tactics is turning the conversation around to the questioner. "Oh forget about me, I want to hear how your weekend was!" she'd say. Of course that won't work for Aunt Bertha, but to her she might say, "This turkey is delicious, how did you cook it?" No one can resist talking about themselves, so just steer the convo their way.
2. Humorously
My Israeli husband likes to say a term in Hebrew, which roughly means, "We are patiently screwing," whose humor does not translate to English, but worked well on his large, rambunctious family. You can also use gentle humor playing on old wives' tales, like, "We're waiting for the stork to drop one on our doorstep," or, "I keep sitting on a toilet after my husband, but that's not working." Or say something bizarre like, "When my therapist deems me sane enough," or "When I'm named as an heir in your will, Auntie…" Although that last one might fall into the next category…
The thing you have to remember—which I could not always do—is to remember that people don't know. They don't know how many couples suffer from infertility, and how hard it is to conceive and stay pregnant.
3. Aggressively
Dealing with fertility is hard enough without people asking you about it, and it's really hard not to lose your patience, after the 50th time. You might be tempted to respond snarkily, like Bridget Jones to questions of her singlehood, "How's your sex life going?" The implication being, I don't ask you about your private matters, so don't ask me about mine. Other rude replies can include, "What, and give up our lazy Sundays and fabulous quarterly vacations for a drippy-nosed kid?" which would be fine if you were planning on being childless by choice, is disingenuous to your true intentions. The thing you have to remember—which I could not always do—is to remember that people don't know. They don't know how many couples suffer from infertility, and how hard it is to conceive and stay pregnant. Their questions are innocent. Which is why you might be tempted to respond…