Blood Test - ESR Results

I have ESR value of 20, the blood test results indicate 0-10 as normal. I gave birth 6 wks ago and am 33 yrs old. Should I be worried? I read on a web site that to calculate the normal value for ESR is the age of the person plus 10 and then divide by 2. Is this correct

[SassyLassie]

The widely used rule for calculating normal maximum ESR values in adults (98% confidence limit) is given by a formula devised in 1983:
ESR (MM/HR)<Age (in years) + 10 (if Female)
                     __________________________
                                        2

ESR reference ranges from a large 1996 study with weaker confidence limits:

(ESR 95% limits) Age (years)
        20 55 90
Men 10 14 19
Women 15 21 23

Yes, that is the correct calculation. Above are "norms for certain ages. The first age is "20" The next age is "55" and the next is "90"