Well I have the unique vantage point to this... giving current happenings with knowing the sex of the baby
I do believe that knowing the sex does help you bond with the baby in some way, at least with me it did... I didn't bond with Tia at all until she popped out... I was convinced that I would loose the baby at some point and not being able to call her , he or she... Made it much easier to distance myself to her...
This time round we were told it was a boy... It took me ages to get used to the idea that it was a little boy, because having a little boy scared me... But I did... I started to bond... I could see him running round my flat with blonde curly hair, asking me for his spiderman pj's, walking into his bedroom and treading on a load of lego, see him coming home from school.. etc... I had a nice little life for him built up... and I bonded... THEN... they said... no no no... It's not a little boy.. It's a girl... and all those dreams got smashed... and I was so depressed the day after ..
Because I had bonded with my little boy and now I had lost him...
So now I am back to square one, I have to start imagining the future with another little girl.. and I have to rebond with her
I think boys and girls are so vastly different creatures its very difficult to imagine the future of your baby if it is an it... And although you can love your bump regardless of its colour, I need to have that ability to see them in the future, to really bond... I love my DD much more now than I did when she was born, and every day I love her more, so being able to imagine the bump in 5, 10, 15 years, makes you see how much they will impact your life and how much more you will love them everyday.
Oh and all this making labour easier as you have a surprise at the end of it... Well.. I had a surprise at the end of my labour with Tia, and it CERTAINLY didn't make it any easier... Just more depressed when my ex got all huffy that it wasn't a boy...
Plus... seeing what Tia looked like for the first time was far more exciting... Its like an internet affair, you've seen pictures, you've spoken to them, but you've never actually met them.. then you do... and that is by far the most exciting thing...