In a macabre case that has made national headlines, the defendant's teenage son discovered the girls' tiny corpses in plastic bags when looking for a frozen pizza.
The 44-year-old housewife Monika Halbe entered the courtroom in the western town of Siegen with her black sweater pulled up to hide her face and did not speak at the opening of the hearing. She followed the proceedings with a distant expression and occasionally wiped tears from the corners of her eyes.
In his opening arguments, Halbe's lawyer Andreas Bartholome read a statement saying that the mother, who already had three children, had been deeply ambivalent about having more babies.
Her family told investigators they never noticed the other pregnancies. Bartholome said Halbe had told him they were "neither intentional nor unintentional," but he noted that his client was "desperately terrified of doctors" and indicated she had suffered some type of sexual abuse that had traumatised her.
"To avoid confronting the unbearable situation of seeing a doctor, she simply waited" when she became pregnant, he said, adding that Halbe suffered from alcoholism.
Prosecutors have charged the mother with two counts of manslaughter for allegedly killing two of the baby girls: one in 1988 and the other between 2003 and 2007. A third girl is believed to have been killed in 1986 or 1987 but the statute of limitations on the case has expired. She could face 15 years in prison if convicted.
When asked in court if she wanted her children to survive after they were born, Halbe slowly nodded, an AFP correspondent reported. "We reject the accusation of manslaughter," Bartholome said.
He told the court that Halbe admitted placing the dead babies in the stand-alone freezer in her cellar, in 1986, 1988 and 2004. "She was not afraid of the babies being found," Bartholome said. "Above all, she wanted to have the babies near her."
The case emerged in May after Halbe's 18-year-old son discovered three tiny corpses wrapped in towels and enveloped in plastic bags when he was looking for a frozen pizza. Halbe's husband and the family's three grown children said they had been unaware of the pregnancies.
The grim case revived a debate about the state of child welfare in Germany after several high profile murders by mothers came to light. Halbe's trial was to continue next week with the testimony of her husband and children.