The study says The body mass index (BMI) was used to classify women as normal weight (BMI = 18.5-24.9 kg/m(2)), class I obesity (BMI = 30-34.9 kg/m(2)), class II obesity (BMI = 35-39.9 kg/m(2)), class III obesity (BMI = 40-49.9 kg/m(2)) or super-obesity (BMI > or = 50 kg/m(2)). If you go to this NHLBI site
you can enter your height and weight and it will calculate your BMI for you.
I was remembering one part of the study and not the other. The odds ratio for women with a BMI equal to or greater than 30 was 2.56 -- this means they are 2.56 times more likely than women of normal weight to develop PE. I called this around twice as likely, although it's really right in the middle between two and three and technically you'd round up to three. Since normal risk is 1:20, we multiply 1 by 2.56 and get 2.56:20, or about two and a half jokers in a deck of 20.
Of course, you can't have two and a half jokers in 20 cards. But you can have 5 jokers in 40 cards. :)
But the thing I didn't mention was the odds ratio for super-obese women with a BMI greater than 50, which was 7.52. So they have seven and a half jokers in a deck of 20, or 15 in a deck of 40.
I got the numbers for risk by gestational risk from the Expert comments here
, but those are for the whole population of women who develop symptoms at that time. In an individual consult, a doc can take your particular set of risk factors into account, and that might well change the estimate of your risk. So, I suspect your risk got downgraded because when they assessed all your underlying conditions, you looked more like a 30% type of person. :)