CBS News Correspondent Steve Futterman reports that Laci Peterson's family is asking that medical facilities keep a watch out for her. On their Web site the family is specifically asking that emergency rooms, obstetric units and private birthing clinics keep an eye out for the 27-year-old.
Police say Peterson's due date isn't changing anything about the way they're investigating the case.
Hundreds of people searched a canal west of Modesto on Saturday. They found several items, including a woman's dress, but nothing appeared to be connected to the missing woman.
Her husband, Scott Peterson, 30, says he found her missing when he returned from a fishing trip.
Police have not named Peterson as a suspect in his wife's disappearance, but attention has focused on him, in part because he admits he told his wife he was having an affair shortly before she vanished.
Peterson says he went fishing at the Berkeley Marina, 100 miles from home, but nobody there remembers seeing him, reports CBS News Correspondent Hattie Kauffman.
He also told Gloria Gomez of CBS affiliate KOVR he was innocent, and urged America to keep looking for his wife.
"If they would just look at their hearts and make the effort to bring her home to her family, I don't care what you think of me," he said.
Laci Peterson was reported seen in Washington late last month.
According to a report in The Daily News of Longview, a clerk told police that a pregnant woman came into the Market Place supermarket and said: "This is serious. I was kidnapped. Call the authorities when I leave."
The 45-year-old clerk said she intended to call police but became distracted and forgot, according to a police report.
The store clerk told police a television news report triggered her memory of an unusual pair of customers who passed through her checkout line. The woman appeared to be in her 20s and in a late stage of pregnancy.
The clerk said the woman was a "classic beauty" with sleek brown hair.
The woman was accompanied by a much older man with "strong features" and a ruddy complexion, the clerk reported.
After the man stepped out of line to get something he forgot, the clerk remarked to the woman that she should be wearing a coat on such a chilly day. The woman told the clerk she didn't have time to take a coat because she was kidnapped. She also told the clerk that the man had a weapon.
The clerk told police she wasn't sure whether to take the woman seriously.
When the man returned, he asked what the two talked about while he was gone, the police report says.
"She said you kidnapped her," the clerk said.
The clerk said the statement seemed to make the man angry, and she teasingly added that her husband always kidnapped her to take her to dinner. The man relaxed and laughed.
"Yeah, I guess I kidnapped her," she recalled him saying.
After they left, the clerk unsuccessfully tried to find a phone book to call police, then became distracted and forgot about the incident. She told police she feels terrible about it now.