Hazel, this is one of the things I am wondering about.
If someone has the choice of taking a legitimate longer maternity break (I suppose arbitrarily, 'longer' here means 2 years), with a structured return to work, does it make them more likely to continue in a career across their lifetime?
More likely than if they want to take more time off than they are legally entitled to, where that entitlement is very short.
This might be a good place to make a distinction between 'work' and 'career' too.
I can think of plenty of women I know who had a baby, found they did not want to return to full time work as early as they would have to, and have been through a variety of big work/family rearrangements to allow them to stay off longer (I'm in the UK btw). That includes finding new work that allows them to work part time or flexibly, or simply having to find a new job when they do start working again. Wracking my brains, that new job is always lower status/less well paid than their previous work. And not 'career' work IYSWIM, in that there's little opportunity for progression.
(to be fair, a couple of people I know have started up their own 'work from home' businesses, but they are very small and early days so I can't tell if this is pin money or serious entrepeneurship)
If those women didn't have such a narrow window of opportunity to rejoin their career, I'm sure more of them would have gone back to what they were doing before (higher status better paid work). As Hazel says, there is a big difference between leaving a very young baby and a 2 year old plus in full time nursery.
To be clear, I am in no way criticising those mums who have 'downscaled' what they do workwise, as long as that is their CHOICE. In the same way I am not criticising the women who return to work early if that is what they WANT.
There must be someone somewhere doing research into this sort of thing - I wish I knew how to find it! Obvs I am just speculating. The more I think about it, the more I realise that I have been very trapped in the mindset of of 'career women have baby, take minimal time off, place young baby in full time childcare and go back to work as if they have never been away'. I can see that a different approach to family leave, state support and attitudes from employers means this might not be the only option. As an aside, from an employer's POV, I would rather employ someone to cover maternity leave for 2 years plus than 6 months, with all the hassle of recruiting and 'bedding in' to a job.
I am mindful of course that legal choice isn't meaningful if economic realities mean families can't take advantage of it, as saralynn has pointed out.