Emma I was teaching with DC1, and booked to go on maternity leave at 38 weeks, I was determined to get my year 11's ready for their Jan exam, so by going then would only miss the last week before Christmas. I was struggling to keep up with the workload physically, especially as there was so much handover work to prepare. And by 37 weeks had to go and see HoD and then Head to ask to go on maternity leave early. Teaching is so physically demanding, and I really overestimated myself!
I was two weeks late with that birth, and it was frustrating.
Incidentally here in the Netherlands I have to have started my maternity leave by 36 weeks. You're not allowed to go further.