# Tag: Pearl index

## Pearl index

INTRODUCTION:

• Pearl index indicates the effectiveness of a contraceptive or is an index of contraception failure.
• Pearl index is called so as it was developed by Raymond Pearl.
• It is used for studying the effectiveness of a contraceptive
• The number of pregnancies includes all pregnancies whether this has terminated as live births, still births or abortions or has not yet terminated.

METHOD:

• In applying the above formula  :
1. The total accidental pregnancies shown in the numerator must include every known conception, whatever its outcome.
2. The factor 1200 is the number of months in 100 years.
3. 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

Three kinds of information are needed to calculate a Pearl Index for a particular study:

• The total number months or cycles of exposure by women in the study.
• The number of pregnancies.
• The reason for leaving the study (pregnancy or other reason).

DRAWBACKS:

• Pearl index is Failure rate/100 women years
• The most fertile couples will get pregnant in the beginning of the study and will no longer be counted in the denominator.
• Couples remaining later in the study, are, on average, of lower fertility.
• With most birth control methods the effectiveness increases with experience.
• The longer a couple is in the study, the better it gets at using the method. So the longer the study length, the lower the Pearl Index will be. Hence comparisons of Pearl Indexes from studies of different lengths cannot be accurate
Exam Question

• Calculation of pearl index is No. of pregnancies X 1200/( Number of women X number of months)
• Pearl Index is a measure of Potency of contraceptives
• Pearl index is Failure rate/100 women years
• Total accidental pregnancy is important in calculaton of pearl index
Don’t Forget to Solve all the previous Year Question asked on Pearl index

## Pearl index

### Pearl index

Q. 1

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
Q. 1

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. A

Explanation:

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 :
1. The total accidental pregnancies shown in the numerator must include every known conception, whatever its outcome.
2. The factor 1200 is the number of months in 100 years.
3. 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

Q. 2

Pearl Index is a measure of :

 A Potency of contraceptives B Fertility rate C Potency of disinfectant D Couple protection rate
Q. 2

Pearl Index is a measure of :

 A Potency of contraceptives B Fertility rate C Potency of disinfectant D Couple protection rate
Ans. A

Explanation:

Potency of contraceptives

Q. 3 Pearl index is
 A Failure rate / 1 women years B Failure rate/10 women years C Failure rate/100 women years D Failure rate/1000 women years
Q. 3 Pearl index is
 A Failure rate / 1 women years B Failure rate/10 women years C Failure rate/100 women years D Failure rate/1000 women years
Ans. C

Explanation:

Failure rate/100 women years

Q. 4

Which of the following is not an indicator for disability?

 A HALE B DALY C Pearl index D Sullivan’s index
Q. 4

Which of the following is not an indicator for disability?

 A HALE B DALY C Pearl index D Sullivan’s index
Ans. C

Explanation:

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.

Note:
HALE – Health Adjusted Life Expectancy
DALY – Disability Adjusted Life Years

Ref: Park’s Textbook of Preventive Medicine, 17th Edition, Pages 22, 351.

Q. 5

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
Q. 5

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. A

Explanation:

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.

Q. 6

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
Q. 6

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. B

Explanation:

Ans. is ‘b’ i.e., Total accidental pregnancy

Q. 7

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

 A 100 B 200 C 300 D 400
Q. 7

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. C

Explanation:

Ans. is ‘c’ i.e., 300

Q. 8

Pearl index is used to calculate:

March, September 2009

 A Accidental pregnancies B Population C Fertility rate D Abortions
Q. 8

Pearl index is used to calculate:

March, September 2009

 A Accidental pregnancies B Population C Fertility rate D Abortions
Ans. A

Explanation:

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.