The attorney for the Houston woman who admitted to killing her five children last week could not confirm or deny a report from a local television station that she is pregnant.

Andrea Yates' attorney told Houston's KTRK-TV's Eyewitness News there is no evidence to suggest she is pregnant. The station had reported a sixth pregnancy, citing inside sources.

Attorney George Parnham did, however, say the results of pregnancy tests will be available later this week.

Yates, 36, who confessed to drowning her five children one-by-one in a bathtub, has been charged with capital murder. Parnham said Monday he would likely seek an insanity defense for his client, describing her as being in a "very deep psychosis." Yates has a history of postpartum depression and attempted suicide two years ago.

Yates remains under a 24-hour suicide watch at the Harris County Jail.

Parnham said he has met with psychiatrists treating Yates, who could receive the death sentence if convicted.

"My observation is that she is still in a very deep psychosis," he told CBS' The Early Show. "We are having her treated and examined by very professional mental health experts who care deeply for their patients."

He said the medication she is on likely will kick in "and there will be some ability to have a rational conversation with her," Parnham told ABC's Good Morning America. "That moment in time has not yet arrived."

Parnham said he is gathering background on Yates' mental health history before making a final decision on her defense.

"I've accumulated evidence in the last 24 hours that strongly suggests that the mental status of my client will be the issue, which means entering a not-guilty plea by reason of insanity," the lawyer told the Houston Chronicle.

He would not say what evidence indicated Yates was insane when she killed Noah, 7; John, 5; Paul, 3; Luke, 2; and 6-month-old Mary.

However, the lawyer said he does not think the case warrants the death penalty and he hopes prosecutors decide against seeking it.

Yates' husband, Russell, has said that his wife's postpartum depression, coupled with her father's recent death, drove her to harm their children.

George Dix, a law professor at the University of Texas, said insanity defenses are rarely used and rarely succeed when they are. To be found innocent by reason of insanity, Yates would have to show that she was so mentally impaired that she couldn't see circumstances for what they were.

For example, if she "believed her children to be devils, she's entitled to acquittal," Dix told The Dallas Morning News in Sunday's editions.

Michelle Oberman, a law professor at DePaul University in Chicago and author of the upcoming book Mothers Who Kill Their Children, said postpartum depression has been a defense element since the mid-1980s.

"The best chance she has, if she's got any good chance, lies in hoping the jury understands the circumstances under which she was operating and to understand the reality of postpartum depression," Oberman said.

About 10 percent to 20 percent of mothers face some level of postpartum depression. Most cases are mild, and can be treated with counseling and medicine. On rare occasions, postpartum depression has been known to cause psychosis or delusions.

Visitation for the five Yates children will be held Tuesday night from 6-8 p.m. at Clear Lake Church of Christ. The funeral will be held Wednesday. Both are only open to family members and friends of the family.

The Associated Press contributed to this report