Carl Boman, who recently received custody of the four children he and the accused murderer had together, told Kansas City television station WDAF that he thinks his former wife needed to come up with a baby to save face.
Boman says Lisa Montgomery had her tubes tied 14 years ago.
Montgomery has been charged with the death of Bobbie Jo Stinnett, who was found dying in her Skidmore, Missouri, home. The baby Stinnett had carried for eight months had been removed from her body.
The baby and Montgomery were found the next day in Kansas. Family and friends said she tried to pass off Stinnett's baby as her own. The child survived and is being cared for by the victim's family.
The custody flap between Boman and the Montgomerys began just days before Lisa Montgomery allegedly killed Stinnett.
Although all of her four children are still under the care of their stepfather and Lisa Montgomery's current partner, Kevin Montgomery, a judge granted temporary custody to the children's birth father.
According to a report in the Kansas City Star, Osage County District Judge Phillip Fromme granted Boman custody Saturday, citing Lisa Montgomery's arrest on a charge of kidnapping resulting in death.
Montgomery has been charged in last week's death of a Missouri woman, who was eight months pregnant when she was killed and the baby cut from her womb.
Court records show that six days earlier, Boman had filed a motion seeking custody of two of the four children they had together. In the motion, the ex-husband reports that the children — ages 15 and 16 — had expressed a desire to live with him and had been "having difficulty" with their mother.
The Star also reports that two days later, Boman said in an amended filing that the custody question had become urgent.
Boman wrote that the actions of the mother are such that the children may be in danger, if not from the mother directly, then from the emotional stress of the situation caused by media coverage of the event.
A final hearing on the change of custody is scheduled next month.
The FBI says Montgomery strangled Stinnett, 23, who was eight months pregnant when she was found dead by her mother on Dec. 16th at her home in Skidmore, Mo., where she and her husband, Zeb, raised rat terrier dogs.
Kevin Montgomery has said he had sent flowers to Stinnett's funeral Tuesday and offered condolences to Zeb Stinnett and his infant daughter. Montgomery said he might get to visit his wife in two or three weeks. He has not spoken with her since her arrest.
After Lisa Montgomery made her first appearance in federal court Monday, Kevin Montgomery said, "I had no idea," when asked by reporters what he had known about his wife's alleged actions. He also expressed sympathy for Stinnett's family.
"This has to be as hard or harder on them as it is on me," he told reporters. "I sure hope they get as much support from their church and community as I have because we are all going to need it."
Local news sources in Missouri and Kansas report that some who know the Montgomerys are asking themselves whether they could have recognized signs that might have indicated she wasn't stable.
Tuesday, hundreds of mourners gathered Tuesday in the small northwestern Missouri farming community of Maryville for Stinnett.
The crowd filled the flower-filled Price Funeral Home and overflowed into the entrance for the service for Stinnett. Cars lined the streets on a bitter cold day, with the mercury dipping into the single digits.
"I've known her since she was a baby," said family friend Carl Montgomery. "She grew up into a beautiful swan."
It was that business that put Stinnett in contact with the woman who is now charged with the murder - Montgomery apparently attended dog shows with Stinnett, and both bred rat terriers. Montgomery was arrested hours after the slaying as police followed a trail that began with data on the victim's computer.
Stinnett and her accused killer were apparently photographed together at a dog show months before last week's attack.
Photos on Bobbie Jo Stinnett's Web site include ones labeled as being from an April 2004 dog show in Abilene, Kansas. One picture shows seven people holding rat terriers: Stinnett at the right, with a purple ribbon, and a woman who resembles Montgomery at the left. There is no caption identifying the people.
Dog trainer Nancy Strudl, of Omaha, Neb., says she was among those at that dog show. She says both Montgomery and Stinnett, as well as Stinnett's husband, Zeb, and one of Montgomery's daughters, are among the seven people in the picture.
Montgomery "told us all she was pregnant with twins, and about a month and a half ago her messages were 'I lost one of the twins. It's so terrible, but they saved one twin,'" Strudl said. "We didn't believe she was pregnant. I don't know how she fooled her family and community."
Family and friends said Montgomery, arrested Friday, tried to pass off Stinnett's baby as her own. The child, who has been named Victoria Jo Stinnett, spent the weekend in a Topeka, Kan., hospital before going home Monday afternoon with her father and another relative.
On Monday, Kevin Montgomery said he believed that the baby his wife presented to him was theirs.