Spain's government will on Tuesday officially present a draft bill giving workers the right to take sick leave due to severe period pain.
The cost of a loss of working hours in such cases would be covered by the state for as long as the pain lasts, the government confirmed on Monday on request.
A consultation with a doctor is required to get the time off work.
Adopting the legislation would make Spain the first country in Europe with such a law.
Equality Minister Irene Montero of the smaller left-alternative coalition partner Unidas Podemos is one of the main forces behind the bill.
It is due to be introduced as part of new regulation on abortion law, which will allow all over-16s to terminate a pregnancy without parental consent.
Some lawmakers from Prime Minister Pedro Sánchez's Socialist Party (PSOE), which leads a minority government, expressed reservations about the bill.
Economy Minister Nadia Calviño warned the regulation could put women at a disadvantage when competing for jobs.
The government would never approve measures that could "stigmatize women," she said.