Get Some Rest
Try taking a nap a few hours before you plan to leave for the office part. If the party is taking place on a work day, go straight home after work and go right to sleep and only wake up when it is time to start dressing for the party. Fatigue during early pregnancy is common, and getting plenty of rest right before the event will help you get through the event without feeling exhausted immediately afterwards.
Stay off Your Feet
Mingling during parties is common and expected, but if you are expecting you should try to stay off your feet as much as possible. Do not worry about being viewed as a wallflower, your coworkers will understand that you need to rest and many will go out of their way to sit with you so that you are not left alone.
Nibble throughout the party to help keep your stomach settled. Waiting too long to eat, or eating too much food quickly, can cause nausea or even vomiting. Avoid getting sick at the party by snacking regularly.
Being pregnant does not mean you have to exclude yourself from holiday gatherings. Resting and eating regularly can help you avoid the fatigue and nausea that make enjoy holiday parties so difficult.