"It isn’t very often that you’re called upon to make a decision that you know will affect the rest of your life, a decision that is irrevocable and defining. I chose to end the pregnancy for what I thought were good reasons, chief among them being my boyfriend’s emphatic unwillingness to be a father." —Margaret Gunther in Modern Love
Personally, I've never been pregnant. I may not even be fertile for all I know; however, I'm paranoid about disease and unwanted pregnancy, so I haven't chanced it. But I did notice a change in my attitude during the time (mid thirties) when I finally, very reluctantly, started acknowledging that I might actually want to have a biological child—something I never imagined for myself...
having decided to live childfree many years previous.
One sign that I was changing, whether or not I wanted to: if a period was late, instead of thinking, "Crap, I'd have to get an abortion if I'm pregnant," now I thought, "Whoah, that imagined termination I always figured I'd have in the case of a pregnancy? No way could I do it now. If I got pregnant, I'd keep it."
I wasn't ready for this new me with her new views on such things. I did take it as a sign that this biological clock thing was hugely real. I told my partner about it, too, so that if it came up he wouldn't even ask if I "wanted to keep it."
In the link above, a 34-year-old woman decides to terminate a pregnancy in large part because her boyfriend doesn't want to raise the child... and later finds herself infertile. Augh.