We did a pros and cons lists, discussed it multiple times, but couldn't figure out what to do. I guess we were waiting until the anatomy scan to decide if we wanted to find out. I tried to make sure that any feelings I had were motivated by what we wanted, not what I thought I should do based on other people in our lives.
We decided to keep the sex to ourselves so it didn't have to weigh the benefits or worry about a gender reveal.
On one hand, I think it's easier to slip up and tell people if you know ahead of time, on the other, if we are having trouble bonding still at that point it could be worth it to find out. We also like old-fashioned things a lot, and I don't want to let unconscious gender prejudices start impacting my views before my kid is even born.
But knowing would make it easier to sew a few gendered items of clothing, and I'm sure I'll want to make one or two outfits like that, despite usually preferring gender neutral clothes for babies.
I know some people feel it's better to burst that bubble earlier rather than at the birth. Most people have a preference, however slight.