I would like to wish a colleague who is going on maternity leave. I have known about the pregnancy for a while now so saying “Congratulations on your pregnancy” doesn’t sound right. All suggestions are welcome.
You could simply write:
Wishing you all the best on your maternity leave.
Take care and enjoy this precious time.
If you are good friends with this colleague then you can write something a little more personal
Hope you enjoy your maternity leave (lucky you, no more rush hour traffic!) I wish you a very happy delivery, and we can’t wait to wait to see your sweet “bundle of joy”.
Take very good care of yourself.
The “we” is an added touch, it suggests that everyone at work is looking forward to seeing the newborn.