It's partly expectations. Dh is fully involved in childcare and has been from day 1. It's not been completely straightforward though and in the early days I did sometimes have to make a concerted effort not to just do things myself, or hover, or criticise if something wasn't exactly how I'd do it - early days make a difference.
I think some of it stems from being in hospital for those first few days, on your own, sink or swim. You come out as the defacto "expert" even after a few days.
Also dh having a decent attitude - I know some partners who have a stinking attitude to childcare, eg not changing nappies or getting up at night. Short of refusing to have children with men like that, not sure what the answer is and I'm glad I don't have to try.
It's also partly down to inequalities in society, again we're quite lucky as a couple in that we have jobs that pay roughly equal (I earn a bit more and also work part time at the moment so would earn quite a bit more if full time jobs were available in my field at the moment) so there's none of the issue with one job being considered "higher status" or contributing the lion's share to the family purse and therefore being harder to take leave from.
For dc2 (due soon) I'm taking 6 months leave and dh is taking 6 months leave. This is a godsend for us and has been pretty easy to arrange. Dh is really looking forward to it, it'll save us 6 months nursery fees and we'll be better off than if I'd taken a year.
The bit where we don't do so well is ad hoc leave for childcare due to sickness etc. Dh is not treated equally to women in his workplace doing the same job. It is assumed (by his employer) that I'll take the time off and they are noticeably less willing to be flexible for male employees. It was the same in his last job. It's difficult to know how much this is down to him being private sector and me being public sector though. My employer has significantly better family friendly policies and is far more transparent in their application.
Dh, however works shifts and this has worked out well for us in being able to be more flexible in the long run. I am as flexible as possible with my employer (eg swapping days if needed, as much unpaid overtime as required, working from home) because I appreciate the flexibility in return and dh's shift patterns give me some leeway. We don't have much family help (50 miles away so emergencies only) so we work it out between ourselves.
We don't have a lot of money, but in some ways (bizarrely) this gives us a bit more choice. I read a lot on here about people who work miles from home, travel a lot for work etc etc etc. We don't have high paying jobs but we both work within a mile of where we live, don't tend to work more than 40hrs in an average week and have no regular travel. We live in a poky flat, but don't have some of the headaches better off people have.
Nursery fees will bite us in the arse again in a year though. We're considering dh working 4 days a week and opposite days to me to save on fees if possible.