Longer distances while pregnant

To answer your question directly - no.  But I did run 37 miles while pregnant w/ my #2.  A couple of thoughts about doing a HIM while pregnant.

Is it possible?  Yes
Is it what's best for mom and the baby?  Answers will vary.  Medically speaking, meh...

A couple of things to think about -

1) if it's your first pregnancy, you have no idea how you will feel.  Some people stay very active right up until the end.  Some people suffer nausea, back or hip pain and are more comfortable toning their activity down.

2)  It is never advised to try and increase fitness while pregnant, but rather to strive to maintain.  Therefore, if you weren't in HIM shape prior to getting pregnant, now it not the time to embark on an aggressive training plan.

3) You have to be willing to 'not' race the event.  Some docs still use a HR guideline, others don't.  Mine does, so I made 100% sure I didn't cross that threshold while running with my little one.  I was also only 4 weeks pregnant at the time I ran 37 miles, had only found 2 days before and was fully trained for the event.

4) Depending on how far along you are for the race, the possibility of crashing on the bike could present a danger.  For this reason, I didn't bike while pregnant.  No matter how careful you are, you can't control those around you.

Not meaning to sound preachy here, but it really comes down to fully accepting that there's a little one inside you, for whom you are solely reasonable.  I struggled with that a lot with my first pregnancy.  Stopping racing seems like such a HUGE sacrifice.  But after having her,  I totally got it.  My races were not important. There's plenty of time for racing later.  Really, there is.  Maybe not right away, but trust that you can always go back.

Hope this helps