I couldn't help but giggle just a little at you men discussing Birth Pangs, since you obviously have never experienced them.  After giving birth 6 times, I happen to know just a bit about the subject, so I thought I would try to enlighten you.
    I think "birth pangs" is referring to contractions, which often start around the 6th or 7th month!  The contractions help the uterus to grow, and help prepare the womens body for the events ahead.  These are known as Braxton-Hicks contractions.  Though these are not part of the labor process, they can be rather strong, and come in succession at regular intervals, just like during labor, though they are generally much further apart (maybe every 15 to 20 minutes, rather than 3 to 5 minutes).  The contractions make the woman's stomach as hard as a basketball, and kind of push the air out of the lungs, which are currently sharing their usually spacious abode with the heart, stomach, and other assorted organs!  When the actual time does come, some women have contraction on a regular basis for 2 - 3 DAYS prior to the baby's arrival.
    When I had my first child, I was in labor for 17 hours!  That was still only half as long as some of the labor periods my mother went through.  I know the biggest reason why my labor was so much shorter than my mother's was because I was given medications which help bring the labor on harder and faster.  These medicines were not available when my mother was having children.  At the time the Bible was written, who knows what a typical labor period was like, since they may not have had anything but wine to offer women for their pain.
    As far as "birth pangs" coming before the rapture, I say YES, most definitely!  All of these earthquakes and such appear to be preparing the earth for the "Big One", just like the contractions do.  Though I am sure that we will be gone before "labor" starts!

God Bless,
Valerie Z.