A woman charged with killing five newborns after hidden pregnancies — and keeping their remains in a locked closet — may seek to be found incompetent to stand trial.

Michele Kalina's public defender raised mental-health issues in court Thursday, delaying the scheduled plea and sentencing of the Reading home-health aide.

Berks County Judge Linda K.M. Ludgate will pursue independent psychiatric testing before ruling on the competency issue. No new court date has been set, and a gag order prevents lawyers from discussing the homicide case.

DNA tests show Kalina, 45, conceived most, if not all, of the babies through an affair with a co-worker that spanned more than a decade. Neither he nor Kalina's husband knew about the pregnancies.

Kalina's teenage daughter found the remains in the closet last year and called police. One set of bones was entombed in cement and the others in a cooler, a plastic tub and a cardboard box.

"It may be the way in which women resolve these dilemmas: 'I'm pregnant again, and I don't want to abort the child. But I don't want anybody to know that I have the child,'" said Geoffrey R. McKee, a forensic psychologist at the University of South Carolina School of Medicine who wrote the book, "Why Mothers Kill."

Women who kill newborns are usually young, first-time mothers who are afraid to reveal their pregnancies, he said. Kalina doesn't fit that demographic, but may share a similar motivation, given the on-again, off-again affair.

Such women are rarely found to be mentally ill, and even when they are, it's often not a factor, he said.

"More often, it's (the death) designed to avoid being detected as pregnant," McKee told The Associated Press on Wednesday.

Kalina is charged with one count each of criminal homicide and aggravated assault, and multiple counts of abuse of a corpse and concealing the death of a child.

She started dating the co-worker in 1997 and soon appeared to be gaining weight. She told him she had a cyst, which she later said had been drained, according to police affidavits. The "cyst" recurred three or four more times over the years, the boyfriend told police.

Kalina, who is petite, had no prenatal care during the five pregnancies, and it's not clear where she gave birth.

In addition to those babies, Kalina had a sixth secret pregnancy that culminated with the 2003 birth in a Reading hospital of a baby girl that she gave up for adoption. That child was also conceived with the boyfriend, DNA tests show.

A prosecutor described him last year as "overwhelmed and shocked" by news of the pregnancies.

Kalina had borne two children with her husband Jeffrey, in 1987 and 1991. The oldest had cerebral palsy and died of natural causes in 2000.

In 2008, the family moved from a house to an apartment, and Kalina allegedly brought the remains with her. She warned her husband and daughter not to open the locked closet, police said.

At work, she held the same job for 15 years, earning praise from both her employer and families of the elderly patients she nursed. Yet she conceded in police interviews that she was an alcoholic, sometimes prone to blackouts.

The U.S. legal system, in recent years, has hardened its view of women who kill their children.

In 1999, 70-year-old Marie Noe of Philadelphia was sentenced to five years of house arrest and 20 years of probation for killing eight babies decades earlier.

"All I can figure is that I'm ungodly sick," Noe said in a police confession, in which she admitted smothering three of her children with pillows.

There is far less empathy today, after a line of U.S. filicide cases that includes Susan Smith, the South Carolina woman who drove her two children into a lake in 1994; Christina Riggs, who smothered her two young sons in Arkansas in 1997; and Andrea Yates of Houston, who drowned her five children in a bathtub in 2001.

Yates is serving a life sentence after the jury rejected her insanity defense. Smith, sentenced to 30 years to life, is eligible for parole in 2025.

Riggs was executed in 2000.

Kalina, like other women accused of infanticide, appears to have been socially isolated. A native of Rockland County, N.Y., she had no extended family nearby, and no close women friends have emerged.

According to McKee, more women killed or abandoned newborns before the advent of legal abortion and safe haven laws. Yet no one really knows how often it occurs today.

"It's still a huge problem in the sense that we really don't know how many abandoned neonates there are," he said.

Kalina's secrets went undiscovered for years, and were only disturbed by her daughter's curiosity, and defiance.

And another nurse's aide, this one in France, admitted last year that she had suffocated eight of her newborns, before burying the bodies in her garden or hiding them in her garage. New owners made the discovery. Dominique Cottrez, 46, told police she'd had a bad experience with doctors with her first pregnancy, and never again wanted to see one again.

Their stories stand out, even in the already disturbing caselaw on women who kill newborns.

"Neonaticides are typically committed by first-time mothers," McKee said. "It's very odd for them to continue to do this."