Tuesday, January 21, 2014

The normal thickness of the uterine wall during pregnancy

In his trial testimony, Dr. Brian Peterson said this about Laci's uterus as he observed it during the autopsy.

PETERSON: Sure. The uterus, in the first place, from the lowest portion of the uterus where it connects to the vagina, to the uppermost portion, the fundus, measured 23 centimeters. That would be roughly ten inches. As I said, normally, a uterus in the non-pregnant state may be the size of a golf ball. So an inch and a half or so. In greatest dimension, this is substantially larger. In the non-pregnant state, the uterus is almost solid muscle. There is obviously a cavity on the inside of it. But just to feel it, to make a section across, it is a relatively solid muscle. This uterus was markedly thin. The thickest, and I measured the wall of the uterus in several locations. The thickest was two millimeters, very small, all the way to nothing. Up near the top of the uterus it actually been, to my eye, abraded, and was open. So up there there was no wall. So the thickness of the wall ranged from nothing to two millimeters. So, in summary, what we have is a uterus that's much larger than a normal, non-pregnant uterus. The wall is much thinner. And as I put those two things together, I determined that that had been a pregnant uterus.

And then later he said,

PETERSON: Well, in terms of why it was the uterus there, perhaps, and other organs weren't, smooth muscle organs like the uterus in a woman, and the prostate gland in a man, tend to be relatively protected down in the pelvis, relatively resistant to degradation. So oftentimes there could be a lot of other parts missing, we'll still have that to help us determine the sex of the person. I guess that would be the main forensic significance. As I said, my other conclusion, based on the uterus, because it was enlarged and was thin, it had been pregnant. Now, at the point that I got this body, there was nothing left in the uterus. So there was no baby in there. There was no placenta in there. But the uterus remained enlarged from having been pregnant.

What he does not say is how thick a pregnant uterus normally is, especially at 32-33 weeks, Laci's stage of pregnancy on December 23, 2002.  The Defense team, and subsequently the jury, had no way to digest the information that the uterus wall was thin, 2mm at the thickest, because it had nothing to compare it to. 

I found a 1998 study that provides the information the Jury needed to draw a correct conclusion about the thinness of the uterine wall.  "Myometrial Thickness in Pregnancy: Longitidunal Sonographic Study",  is a study using ultrasound to measure the thickness of the uterine wall in 28 patients at different times during the course of their pregnancies.  These were normal pregnancies.  No difference was noted between women in their first pregnancy or in multiple pregnancies.  Laci was in her first pregnancy.  Average age of the women was 28 years, with the range from 19 to 41 years.  Laci was 27 years old.

Figure 3

Uterine wall thickness (in mm) during pregnancy. The continuous line represents the mean and the dashed lines represent the upper and lower 95% confidence intervals.  A, Anterior lower segment; B, mid-anterior wall; C, fundal wall; D, posterior wall; E, right wall; F, left wall. 
Click on the chart to enlarge it.  If you still have trouble reading it, here's a summary in data form. 

A:  7.4 mm with a standard deviation of 1.8 mm
B:  9.13 mm with a standard deviation of 1.6 mm
C:  9.48 mm with a standard deviation of 1.5 mm
D:  10.06 mm with a standard deviation of 1.9 mm
E:  8.95 mm with a standard deviation of 1.6 mm
F:  9.05 mm with a standard deviation of 1.5 mm

There's a substantial difference between the thickness of a normal uterine wall during pregnancy, and the 0-2 mm thickness of Laci's.

Dr. Peterson should have provided this information in his autopsy report, and Mark Geragos should have consulted an expert to see what it meant.  If it makes a difference in Scott's favor, as I suspect it does, Scott was entitled to have that information presented to the jury. 

If Dr. Peterson wasn't familiar with the subject, he should have done some research.  He had time between when he did the autopsy and he completed his report.