I must admit I came at this from a slightly different angle, so don't slate me. I am a City mum and have been for over 25 years and I have 3 children. I planned to work up to about 3 weeks before my first child (investment banking), but unfortunately my dd decided to arrive very early, so I had to leave at 28 weeks. I did take the six months off, mainly because the first month was spend in NICU.
I went back full time, but after about 18 months the impromptu travelling (go home and get your passport, you're off to NY tonight!) didn't really gel with a full time husband and a fantastic nanny. So I went to 3 days with another organisation.
Part time does work if you work it properly.... I was never contactable on my days off (well contactable, obviously, but not for rote work or meetings), I worked very late on Wednesday to finish up and leave notes for my team, then I closed my book and left! I know some of you won't agree with this approach, but it worked for me. I was promoted to MD and went up to 4 days a week and did that for a few years.
I took a couple of years off when family circumstances changed and have now gone back 2.5 days a week, still in the City.
Basically, my mantra was to fix what I wanted to earn (pretty much the figure mentioned above) and then work the appropriate number of days to earn it. I know it's not the 'Lean In' attitude at all, it's more the 'Work to Live, not Live to Work', but I've found part time work very accommodating in that respect. Now my children are growing up, I might do a couple of extra days to bolster up income and take on more management.
I agree that a helpful dh and a great nanny is key to success, but as long as you are clear with your employer the extent of your role and what you are prepared to do, part time and high earning is possible.