Contractors were never entitled to maternity pay in the same way employees are, whether inside or outside IR35. Like other self employed women they may be entitled to maternity allowance provided they’ve made class 2 NI contributions during a qualifying period.
The alternative is that they become an employee. This will give them all the rights of employees, sick pay, maternity pay etc however this isn’t an attractive option as (inside or outside IR35) the contractor rate is usually substantially higher than that of a permanent employee.
Contractor Uk can be a great site but it’s also massively biased as contractors didn’t want the IR35 reforms to come in. Nothing has changed, as self employed people have never had maternity rights so can’t be stripped of them.