Approximately 25% of women are not able to take their full maternity leave period, even though technically it's been expanded to a year. Those are women who, on average, have incomes of $16,000. The whole group of the 25% earn $20,000 or less, or if they are not single parents, they, with their partner or husband together, earn no more than $40,000 per year. So it's clearly the financially stressed group. There are also figures that show that if a woman has a permanent, full-time job she will almost certainly take the full one-year maternity leave--98% do so. It's well documented.
On February 24th, 2009. See this statement in context.