The short answer
In most workplace schemes, your own and your employer's regular contributions stop when pensionable pay stops. The pension already built remains yours, but the break can reduce the fund available later and may affect your State Pension record. Check both before you decide.
A career break has more than one pension effect. There is the contribution you do not make, the employer contribution you may not receive and the future growth those payments might have earned.
The position depends on your scheme rules, employment status and PRSI record. That is why the questions are more useful than a generic percentage.
Ask before the break begins
The pension impact belongs beside the income, childcare, tax, career and family consequences. It should not be used to frighten someone out of a necessary life decision. It should be visible before the decision is made.