Pearl index
Which of the following is correct for the calculation of pearl index :
A 
No. of accidental pregnancies X 1200 No. of patient observed X months of use 

B 
No. of accidental pregnancies X 1200 No. of patient observed X 2400 

C 
No. of patients observed X months of use No. of accidental pregnancies 

D 
No. of patient observed X 2400 No. of accidental pregnancies X 1200 
Which of the following is correct for the calculation of pearl index :
A 
No. of accidental pregnancies X 1200 No. of patient observed X months of use 

B 
No. of accidental pregnancies X 1200 No. of patient observed X 2400 

C 
No. of patients observed X months of use No. of accidental pregnancies 

D 
No. of patient observed X 2400 No. of accidental pregnancies X 1200 
Ans. is a i.e. Number of accidental pregnancies X 1200/ Number of patient observed X months of use
 Pearl index indicates the effectiveness of a contraceptive or is an index of contraception failure.
It is expressed in terms of
Total accidental pregnancies x 1200 (12 x 100)
 Failure rate per HWY No. of patients observed x Months of use
 In applying the above formula the following points must be kept in mind :
 The total accidental pregnancies shown in the numerator must include every known conception, whatever its outcome.
 The factor 1200 is the number of months in 100 years.
 The total months of exposure in the denominator is obtained by deducing from the period under review of 10 months for a full term pregnancy and 4 months for an abortion.
Lets understand this by an example.
Suppose 100 couples have used a method for a period of 2 years and have resulted in 20 pregnancies, the
20 x 1200
Pearl index is = 10 100 x 24
Pearl Index is a measure of :
A 
Potency of contraceptives 

B 
Fertility rate 

C 
Potency of disinfectant 

D 
Couple protection rate 
Pearl Index is a measure of :
A 
Potency of contraceptives 

B 
Fertility rate 

C 
Potency of disinfectant 

D 
Couple protection rate 
Potency of contraceptives
A  Failure rate / 1 women years  
B  Failure rate/10 women years  
C  Failure rate/100 women years  
D  Failure rate/1000 women years 
A  Failure rate / 1 women years  
B  Failure rate/10 women years  
C  Failure rate/100 women years  
D  Failure rate/1000 women years 
Failure rate/100 women years
Which of the following is not an indicator for disability?
A 
HALE 

B 
DALY 

C 
Pearl index 

D 
Sullivan’s index 
Which of the following is not an indicator for disability?
A 
HALE 

B 
DALY 

C 
Pearl index 

D 
Sullivan’s index 
Pearl index is a measure of effectiveness of a contraceptive method. It is expressed as failure rate per 100 woman years and is not related to disability.
HALE – Health Adjusted Life Expectancy
Ref: Park’s Textbook of Preventive Medicine, 17th Edition, Pages 22, 351.
Failure rate of contraceptive method is determined by
A 
Pearl index 

B 
Half 1 ife 

C 
Number of accidental pregnancies 

D 
Period of contraceptive practice continued 
Failure rate of contraceptive method is determined by
A 
Pearl index 

B 
Half 1 ife 

C 
Number of accidental pregnancies 

D 
Period of contraceptive practice continued 
Ans. is ‘a’ i.e., Pearl index
Pearl index
o Contraceptive methods are evaluated by Pearl index
Pearl index is “failure rate per hundred women years of exposure (HWY)”
Failure rate per HWY — 
Total accidental pregnancies 
x 1200 
Total months of exposure 
o In applying the above formula, the total accidental pregnancies shown in the numerator, must include every known conception, whatever its outcome. The factor 1200 is the number of months in 100 yrs.
o A failure rate of 10 per HWY would mean that in the lifetime of an average women about one fourth or 2.5 accidental pregnancies would result, since the average fertile period of a women is about 25 yrs.
Which of the following is important in calculaton of pearl index –
A 
Number of abortions 

B 
Total accidental pregnancy 

C 
Socioeconomic status 

D 
Total gestational period 
Which of the following is important in calculaton of pearl index –
A 
Number of abortions 

B 
Total accidental pregnancy 

C 
Socioeconomic status 

D 
Total gestational period 
Ans. is ‘b’ i.e., Total accidental pregnancy
100 women, followed up for 20 months, with OCPs, 5 became pregnant, Calculate the Pearl Index –
A 
100 

B 
200 

C 
300 

D 
400 
100 women, followed up for 20 months, with OCPs, 5 became pregnant, Calculate the Pearl Index –
A 
100 

B 
200 

C 
300 

D 
400 
Ans. is ‘c’ i.e., 300
Pearl index is used to calculate:
March, September 2009
A 
Accidental pregnancies 

B 
Population 

C 
Fertility rate 

D 
Abortions 
Pearl index is used to calculate:
March, September 2009
A 
Accidental pregnancies 

B 
Population 

C 
Fertility rate 

D 
Abortions 
Ans. A: Accidental Pregnancies
Methods of contraception are compared by the Pearl index. A high Pearl index stands for a high chance of unintentionally getting pregnant; a low value for a low chance.
The Pearl index will be determined by the number of unintentional pregnancies related to 100 women years. E.g. 100 women can contracept for 1 year each with the method that is going to be examined. If three pregnancies occur during this period in this group, the Pearl index will be 3.0.