Hajar Raissouni writes for the Arabic-language daily Akhbar Al-Yaoum, which has a history of run-ins with the authorities.
She was arrested as she left a clinic in Rabat where her lawyer Saad Sahli said she had been undergoing treatment for internal bleeding.
But the 28-year-old was examined by a medic and the prosecution said she showed signs of pregnancy and of having undergone a “late voluntary abortion”.
In a statement, it insisted her detention had “nothing to do with her profession as a journalist”.
On Friday, Rights groups urged Moroccan authorities to immediately release her, as her lawyers have firmly denied the “illegal abortion” charge.
Raissouni, who is religiously but not yet legally married, is also accused of having “sexual relations outside marriage” and faces a court hearing on Monday.
Her lawyers are lodging a complaint against police for forcing her to have a medical examination, her uncle Souleymane Raissouni told AFP.
Also arrested were her fiancee, a doctor, a nurse and a secretary.
Human Rights Watch and Amnesty International on Friday joined social media users in calling for her release.
“Instead of intimidating Hajar Raissouni by prosecuting her on unjust charges, the authorities should immediately and unconditionally release her,” said Heba Morayef, Amnesty’s regional director.
Ahmed Benchemsi, regional communications director at HRW, echoed Morayef’s call for all charges to be dropped.
The case had “a whiff of political manipulation since the defendant is a reporter from one of Morocco’s last newspapers,” he said.
Touafik Bouachrine, the owner of Raissouni’s newspaper, was sentenced in November to 12 years in prison on charges of rape and other offences.
He also denies all charges and his lawyers say his trial was politically motivated.
Raissouni’s arrest sparked heated debate online, and some 150 journalists signed a petition against “campaigns of defamation” against her.
Moroccan law punishes abortions with up to five years in prison, except in cases where the life of the mother is in danger.
However, NGOs say up to 800 women have clandestine abortions every day in the North African country.
