Laci Peterson's Modesto obstetrician rebutted widely discussed reports that the pregnant woman had a sonogram Dec. 23, shortly before authorities believe she was killed.
The revelation could shake a recently floated defense theory that hinges on the age of Laci Peterson's unborn son, Conner, at the time she disappeared.
Despite a court-imposed gag order on the case, a leak to People magazine last month generated hours of speculation on several TV news and talk shows. The magazine, without citing a source, reported that an unidentified doctor had performed an ultrasound on Peterson on Dec. 23.
Other leaks -- again, hashed out on TV -- suggested that Conner's body had aged a few weeks beyond the size suggested by the supposed sonogram.
Dr. James Y.K. Yip confirmed Tuesday evening that he saw Peterson on Dec. 23, but he said the visit did not include a sonogram.
"There was no ultrasound picture of the baby that day," Yip said. "It was a routine prenatal visit for her."
Peterson's husband, Scott, has been charged in the deaths of mother and son, whose bodies were recovered in April along the eastern edge of San Francisco Bay. Prosecutors are seeking the death penalty. A preliminary hearing is set Oct. 20.
A source close to the double-murder case said Peterson had a sonogram in September, about three months before she went missing. She would have been about five months pregnant in September.
Forensic pathologist Harry J. Bonnell of San Diego said a Dec. 23 sonogram would have been extremely valuable for comparison with Conner's body. But experts still might predict with some accuracy Conner's size at that point -- and beyond -- by using the September sonogram, Bonnell said.
That could be crucial to Peterson's defense, if experts determine that Conner lived longer than Dec. 23, said former New York City medical examiner Dr. Michael Baden. He noted that Peterson came under law enforcement scrutiny after his wife disappeared.
"The issue here is how old the baby was," Baden said. "If the baby lived, that means Laci lived also."
His comments were made before the revelation that Peterson's last sonogram was in September.
"If (a doctor) can testify that the baby grew six weeks after (Dec. 23), that gives Scott an absolute out," Baden said. But he noted that an obstetrician's estimate on fetal age could be wrong by several weeks.
From 32 weeks until birth
fetuses typically double in weight, Baden said. There can be wide variations in the rate of the increase during that period, making sonograms less reliable for determining age in those cases, he said.
A more accurate method, Baden said, is X-raying bones for calcium deposits that form as cartilage hardens into bone while the fetus develops.
Peterson's defense team X-rayed Conner's remains earlier this month before coroner's deputies released the bodies to Laci Peterson's family.
Bonnell said either side could find experts to contradict the other.
"If you've got somebody that can throw big bucks at (some) experts," Bonnell said, "they'll tell you what you want to hear."
Bee staff writer Garth Stapley can be reached at 578-2390 or firstname.lastname@example.org.
Bee staff writer John Coté can be reached at 578-2394 or email@example.com.