Chansa Kabwela sent the photos to the vice-president, among others
Two Zambian journalists have been charged with contempt of court after publishing an article in support of their news editor who is on trial.
The journalists say charges against Chansa Kabwela - that she distributed obscene material - should be dropped.
She sent photos to government members showing a woman giving birth without medical help during a strike in Zambian hospitals in June. The baby died.
She says she was exposing health issues and urging nurses to end a strike.
President Rupiah Banda has branded the pictures, published by The Post, the country's biggest selling newspaper, pornographic and demanded a police investigation.
Earlier the government barred rival activists from attending the trial.
It said they would no longer be allowed in court after police had to intervene following scuffles between government supporters and Ms Kabwela's sympathisers.
Prosecutors in Ms Kabwela's trial complained about the article, prompting magistrate Charles Kafunda to bring charges against the newspaper's editor-in-chief Fred M'membe and journalist Muna Ndulo.
They are expected to appear in court on Wednesday.
Ms Kabwela did not publish the controversial photographs, but sent copies to a number of prominent people and women's rights groups, along with a letter calling for the strike to be brought to an end.
The defence is arguing that the case rests on the definition of obscenity and so witnesses should have to describe what counts as obscene and arousing.
The BBC's Jo Fidgen in Lusaka says the pictures are graphic, showing a woman in the process of giving birth to a baby in the breech position - when the baby's legs come out first.
Its shoulders, legs and arms are visible, but the head has not yet been delivered.
The photos were apparently taken in the grounds of Lusaka's main hospital.
The nurses were on strike and the woman had been turned away from two clinics.
By the time doctors operated, the baby had suffocated.
Ms Kabwela says she was given the photographs by the woman's relatives.
President Banda expressed his outrage at a news conference, calling the photographs pornographic.
Pornography is illegal in Zambia and Ms Kabwela was arrested soon afterwards and charged with distributing obscene material with intent to corrupt public morals.
She faces five years in jail.
In her view, and in the view of campaigners for press freedom, the case is political.
The Post has relentlessly pursued the government with allegations of corruption and the president has made no secret of his dislike of the paper, our correspondent says.