I think you'll find, if you talk to a lot of women who have looked for jobs after taking 6+ months off to deal with having a kid, that this is not true.
I'm in the UK so maybe things are somewhat different here with regards maternity but all women I have worked with who have taken time off for this have been given their job straight back once they are ready to return and are usually paid some % of their salary while they were off (I think the law mandates this).
I think that's a positive attribute of the UK system. But consider this: childbirth is a reason many women everywhere temporarily leave the workforce --- not for maternity leave, but literally surrendering their job, perhaps for a couple years. The research we're talking about today shows that after leaving the workforce for a couple years, they face an obstacle that makes it harder to find a new job, and thus more likely that they'll accept an inferior job.
That's certainly true, it took my mother ~5 years to get back into her industry after having kids and even then it was lower in the org chart than she left at.
I would still posit that reasonable people would be more sympathetic to a mother spending 2 years looking after children than a single guy playing a 2 year xbox marathon though.
