Tips for training pregnant women - first trimester

I would get clearance from her doctor and be very aware of how high her heart rate gets along with having clear concise communication with this client at all times during her workouts as being pregnant demands different energy systems at different times.

I would also follow ACSMs guidelines

All pregnant women should strengthen their deepest abdominal muscle, their Transverse Abdominis, or TvA, to prevent common pregnancy related complaints and complications such as diastasis recti (abdominal separation), back pain, and pelvic instability. As an added benefit, because the TvA is the primary expulsion muscle, maintaining strength in this muscle greatly aids in the pushing phase of labor.
BeFit-Mom

All of the answers provided are great! In addition to what's already been said I just want to share my own experience w/ being pregnant & working out... I was already conditioned to high intensity exercise & my doctor told me I could continue doing what I had already been doing w/ the exception after the 1st trimester no lying flat on my back exercises. I remember a man at the gym telling me my baby would be strong b/c of my working out - at the time I thought he was being funny but sure enough my little girl came out strong & 3 yrs later still strong. She even has nice definition in her shoulders it's awesome! After the 1st trimester was over I did a lot of mid-line cable chops for abs & let me tell you my obliques were crazy strong (lol) I also did standing cable crunches w/ the rope attachment. I'm sure my strong core played into my easy birth. I had my daughter at home w/ NO complications! With all that being said if your client has been training before pregnancy continue to train her as usual just adjusting her positioning as she moves through her trimesters!

Id say stay within paramaters set by medical professionals and shoot for the sky.

As always, get physician approval for her to continue working out at the same intensity. You may even want to give your client a copy of a workout you're currently doing so the physician knows what intensity, frequency and duration your client is currently working out at. For most women who become pregnant they can continue to workout at the same intensity.

As her pregnancy progresses, you'll want to be able to modify her workout. Taking out higher impact exercises for lower impact ones for example. You'll also want to keep the lines of communication with both her and her physician open through the duration of her pregnancy. You mentioned that she just found out she was pregnant, so she may still be grappling with the fact that she's pregnant, not wanting her lifestyle to change, not yet experiencing any pregnancy symptoms. That an change quickly. I often ask my pregnant clients how they're feeling before we start, any adverse effects, how did they tolerate the last workout, how are they sleeping, Eatting, about any info from their last doctors appt., etc. Be prepared to change the workout at any time. The more you know about how they're handling the changes of pregnancy, the more you'll e able to help her with her desire to continue working out.

You'll want to watch her heart rate, be sure she's not getting over heated and that she's not overdoing it. Watch flexibility with hormonal changes as women who are pregnant tend to get over flexible in their lower limbs in prep for birth. As someone else mentioned continue to train her core and transverse abdominals as these are important to support the growing weight of the baby.

ACE offers some great prenatal CEUs. A good book is Fit to Deliver by Karen Nordahl (there is also a CEU option with the book).

Good luck! And have fun!