Calling in sick in your first trimester?

Ladies,
How did you guys do it?? Did any of you have to call in sick during your first trimester?  I have a pretty flexible job, but I don't ever call in sick (or get sick) and my boss and company doesn't know yet. We're 2 months tomorrow so we're waiting until I go away on a business trip next month to inform them all. I woke up today feeling fine, then ate breakfast and slowly went downhill from there. Struggling to get moving and push through the nausea. Oy. 
How did you guys manage this? I'm worried if I start calling in sick, they may get suspicious! 
Advice. Input.