INDIANAPOLIS — Three-week-old Kevin fussed in mother Melissa Lankey's arms until she started singing softly to him, "Jesus loves me, this I know, for the Bible tells me so." The newborn began dozing within seconds.

"That's kind of our little song. It usually calms him right down," Lankey said.

Lankey did not sing the tune in the baby's bedroom. She was behind bars at the Indiana Women's Prison, where a new program allows some inmates to keep their newborns in their cells for up to 18 months.

The program debuted last month, becoming the sixth in the nation in a growing trend among state prison systems.

New York has had prison nurseries for more than a century; Washington, Ohio, California and Nebraska started ones in recent years, and West Virginia is preparing to launch one, too.

The programs come at a time when the nation's female inmate population is rising.

The Bureau of Justice Statistics shows the number of women in prisons and jails jumped from more than 163,000 in 2000 to nearly 210,000 in mid-2006, fueled largely by an increase in drug convictions that carry mandatory sentences.

Many of those inmates are mothers who experts say benefit from staying with their children, even if it's behind bars.

The Ohio Reformatory for Women in Marysville, whose nursery program Indiana modeled, has seen 14 of its 128 participants re-offend, an 11 percent recidivism rate compared with the institution's rate among all inmates of about 30 percent, spokeswoman Elizabeth Wright said. New York also has seen a dropoff, said Linda Foglia, spokeswoman for that state's Department of Correctional Services.

Indiana hopes for similar results with its program, funded through a $122,000 grant from the U.S. Department of Health and Human Services.

The Wee Ones Nursery at the 136-year-old Women's Prison is open to up to 10 imprisoned mothers who are the legal guardians of their children, have never been convicted of violent crimes, and have less than 18 months left on their sentences.

The nursery staff includes a pediatrician and a nurse. Inmates who serve as nannies must have nonviolent offenses and reading levels of eighth grade or higher; they also must complete a parenting class.

The mothers receive courses on postpartum care, child development, shaken baby syndrome and other topics.

"We hope that we'll continue to make the family the unit that it should be and strengthen those that are going back out into the community," prison Superintendent Zettie Cotton said.

Some critics contend keeping a baby in prison punishes the child for the mother's offense. When West Virginia's House of Delegates debated creating a nursery program last year, opponents warned it might harm the children involved.

But studies show the children benefit from the contact, said Mary Byrne, a Columbia University nursing professor who is conducting a study of 100 children born at the adjacent Bedford Hills and Taconic Correctional Facilities in Westchester County, N.Y.

Byrne said children separated from their inmate parents run higher risks for emotional and behavioral disorders, school failure and trouble with the law. The babies born to mothers in prisons generally are better off staying there with them, she said.

"The outcomes are promising, if the prison nursery programs have the appropriate resources," Byrne said.

Serena Garduza said the Indiana nursery, an extension of the medium-security facility's Family Preservation Program, gives her infant son a better shot at success in life than she had.

Garduza, 31, grew up in foster care after being taken away from her mother, with whom she has lost touch. She stayed in school only until the ninth grade. On probation for theft and receiving stolen property, she was sent to the prison last December after testing positive for cocaine and gave birth to Ramerio, her fifth child, four weeks ago.

Garduza and Ramerio now share a cell with a lone window barred by rounds of razor wire — a stark contrast to the crib, bright white curtains and stenciled moon and stars on the powder blue cinderblock walls.

"I know I'm in prison and all that, but I kind of put my mind out of it," said Garduza, who's due to leave prison this summer. "When he's with me, I really don't feel like I'm incarcerated."

The program recognizes that people make mistakes, said Jennifer Pope Baker, director of the Women's Fund of Indiana, which picks up parts of the costs of the nursery and the Family Preservation Program. Clothing, diapers and other items are donated.