Dear appropriate people at my place of work:
I wanted to take a moment and let you all know that after much consideration I have decided not to come back to work at this time. I whole-heartedly hope that when my girls are a little older and the time is right I may be able to return to the [place of work] and work with all the wonderful people I have been so lucky to share company with over the last year. I appreciate how supportive and understanding you all have been during my pregnancy and maternity leave and sincerely look forward to being a part of the [place of work] family again.
I did not sign it with an evil little icon of a smilie doing a happy dance while tearing up employment papers… I simply signed off tastefully and let my life as an employed person disappear.
Now for my next trick…