Maternity leave

You can take it starting from 6 weeks before your due date, but then you'll have less leave left after the birth.
If you work in a shop, you'll be walking/standing a lot, so those 6 weeks might feel nice. At an office (where I work myself), you're sitting a lot more, so 4 weeks might be the better choice. But it all depends on the soon-to-be mom, of course. In any case, if you can't manage until the 'regular' leave period, you can report yourself as sick. I believe this is considered pregnancy-related for the employer (you might need a statement from your midwife or doctor), so they don't have to pay for it themselves. But I'm not 100% sure about that last part; I didn't experience this with my first.
By the way, you can't exactly predict/schedule the length of leave after your birth. If you go overdue, those days/weeks are added to your leave. So if you're, for example, 1 week overdue, you'll get 1 extra week of leave.

If you get sick due to your pregnancy, UWV pays you sick leave benefits, so it doesn’t cost your boss anything, indeed.
The downside is that you’re required to take 6 weeks off in advance. So you can’t keep working longer than that.

If you can keep working normally, you can choose how many weeks in advance you stop: 4, 5, or 6 weeks. You need to inform your employer at least 3 weeks before you want to stop.

I also work in a shop and I can already tell (28+4) that I won't be able to hold out until 36 weeks! So I'll stop at 34 weeks if I even manage that... so I'll only have 10 weeks after the birth, too bad but it is what it is!

xkruimel

After maternity leave, it also applies that if you report sick due to pregnancy-related issues, your employer doesn't have to pay for it. So if you're not fully recovered after 10 weeks to pick up your work duties, there's a safety net for that.
Additionally, you can take parental leave (your employer must agree to half of your contracted hours, and any other distribution can be arranged with your employer), but this is unpaid for most jobs. It could be a solution if your full number of contracted hours is still too much, but you still want to start working and can, and/or if you simply want to spend more time with your baby for a while.