Glad to join a thread to talk about these things. skiptonlass, there's no clear answer here. You may feel very differently when dc arrive; you may decide to find another job or career path, or may not even want to go back to work. You just can't know and it will have a lot to do with how hard you find the first year (my DD didn't sleep through the night until she was two...)
For my part, I have a 2.5 year old. I've been putting off TTC#2, not least because I am aiming for a promotion to director which I had expected to have last year, but due to some major changes in the company didn't happen. I have a demanding job which I used to be able to stay late to finish if necessary but now of course I have to deal with childcare pick ups. I also travel overseas every 3 months and the trips require a lot of work, so it's an endless cycle of preparation then follow up. And unfortunately my DH is military and away A LOT, unpredictably, ranging from one night to several weeks on not much notice. So I am definitely the default childcare person if DD is ill or it is holidays (he has 4 years left and anyway is paid much more than me, though my pay is being addressed which is another thing to stick around for).
I also work for an American company but in the UK. Usually people are back after mat leave within 3 months, or not at all. I took 12 months (and my word I needed to - I was completely sleep deprived and struggling; around 10 months old was the worst). Plus when I went back I had to travel and was still feeding DD so I had to pump, which never really worked for me, and I was in complete pain for 4 days on the first away trip). No one had ever taken mat leave from the European office before.
All I could do was work my socks off to continue my work after my mat leave and keep pushing through improvements and initiatives. I'm very fortunate that my company is generally supportive (poor pay but decent benefits and flexible working) but they also know that I get back on email in the evenings after I've gone home and I work a lot of extra days for the trips.
I started out working 3 days a week and am now on four but one is from home (DD in childcare some of the day). To be honest, my company and I just proceeded on the assumption that it WOULD work and made it happen. It is very, very different in a hostile environment and frankly I couldn't hack it if I were being criticised, all the while knowing how hard I work all day and evenings, compared to some people who are much less efficient despite being physically in the office for longer hours.
A friend of mine worked a high pressure job at Bloomberg; she worked really hard to make it work but even 12 hour days weren't enough. In the end she left and has set up her own business as a professional coach. It seems to be going really well.
In any case, I am dithering completely about TTC. I have some major trips planned for next year which just wouldn't be an option. I find childcare/pre-school/school difficult enough to manage with one child, never mind two. And at the moment my husband has to take annual leave to be in the country when I am out of the country, so we hardly see each other and it is taking an incredible toll on our toddler to see her parents disappear off all the time.
We've sort of decided to start trying in December though. Eek.