I think mothers working part time here is very common. I don't work so i cannot really comment on my experience but in my husband's office there are many women i know who changed from full-time to part-time after having a child. I also met another colleague of my husband's who is expecting a baby this August and she said that she has already informed her supervisor that when she gets back to work after the maternity leave she will be working only 60% and it seems he is now looking for an addition to the team to cover up for the 40%. I think you should just talk to your supervisor and see what is the procedure/policy for full-time to part-time work in your office.