13 Infertility: impact on population growth

Suniti Yadav and Gautam Kshatriya

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CONTENTS

 

INTRODUCTION

1.       Determinants of Fertility

a.       Biological determinants

b.      Socio-cultural determinants

c.       Behavioral determinants

2.       Definition of Infertility 

3.       Types of infertility 

a.       Primary infertility 

b.      Secondary infertility 

4.       Male infertility 

5.       Patterns of population growth 

a.       Positive growth 

i.      Rapid growth 

ii.      Slow growth 

b.      Zero growth 

c.       Negative growth 

6.       Impact on population growth

 

LEARNING OBJECTIVES

  • To understand the determinants of fertility.
  • To understand the meaning of infertility.
  • To understand the types of infertility.
  • To understand the types of population growth patterns.

    INTRODUCTION

 

Fertility is one the demographic components of population growth and its most important driving force. Fertility determines the number of people for the earth as a whole. Fertility has a direct effect on the growth, size and structure of any population. Fertility has been designated as a positive force through which populations expand, counteracting the negative forces of mortality. If the rate of fertility decreases and is not equal to or greater than the mortality rate, the population may face the danger of becoming extinct.

 

Apart from the effect on the size and growth of the population, the age pyramid or the age structure of the population is also affected. Adequate or high fertility rate implies an age pyramid or age structure which is weighted towards the younger groups. Therefore the determinants of fertility can be categorized as –

 

1.       Biological determinants – The biological determinants of fertility may be defined as the variables that affect the biology of the being and hamper in the normal conception and delivery of an infant. This may include age and infertility.

 

2.       Socio-cultural determinants – The socio-cultural determinants are those factors that are governed by the society or culture or are by choice of the individuals who plan to have an offspring. This may include socio-economic status, family size and culture.

 

3.       Behavioral determinants – Behavioral determinants include factors that affect the behavior and response of the person in response to the biological and socio-cultural determinants. Such factors include psychological and emotional reasons as – depression, anxiety, mood swings etc.

 

Biological determinants of fertility play a major role in shaping the population growth. Age is a biological inhibition on fertility but infertility is an involuntary forced cease on the production of an offspring. Inspite of a couple (a male and a female) being in normal reproductive phase age but not able to reproduce hints towards their inability to reproduce. Therefore, either or both of them may be infertile.

 

Definition of Infertility

 

“Infertility is a disease of the reproductive system defined by the failure to achieve a clinical pregnancy after 12 months or more of regular unprotected sexual intercourse”. Infertility is calculated as the percent of women who seek a child and as the percent of all women of reproductive age.

 

Female infertility accounts for a majority of infertile couples (30-60%) followed by male infertility (30-40%) and almost 10-30% attributable to both male and female infertility and are unexplained (Kara and Simone, 2010). Several reasons like hypogonadism, obstructions, ovulatory obstructions have been reported to be the cause of infertility in males and females (Figure1.)

 

Types of infertility

 

1.       Primary infertility – Primary infertility is defined as the absence of a live birth for women who desire a child and have been in a union for at least five years, during which they have not used any contraceptives. The prevalence of primary infertility is calculated as the number of women in an infertile union divided by the number of women in both infertile and fertile unions, where women in a fertile union have successfully had at least one live birth and have been in the union for at least five years at the time of the survey (Mascarenhas et al., 2012).

 

2.       Secondary infertility – Secondary infertility is defined as the absence of a live birth for women who desire a child and have been in a union for at least five years since their last live birth, during which they did not use any contraceptives. The prevalence of secondary infertility is calculated as the number of women in an infertile union divided by the combined number of women in infertile and fertile unions. Women in a fertile union have successfully had at least one live birth in the past five years and, at the time of the survey, have been in a union for at least five years following their first birth (Mascarenhas et al., 2012).

Figure1. Causes of infertility in males and females

(Source: Kara and Simoni, 2010)

 

High fertility or fertility rate more than the mortality rate is required for population growth. Therefore, it may interpreted that infertility, if exists at a prevalence rate more or equal than the birth rate, may lead to decline in population size. The population growth may be retarded and the shape of the normal population pyramid may change. A normal population pyramid may seem to be inverted if high infertility prevails in a population.

 

Male infertility

 

Male infertility may be defined as inability of a male to make a female pregnant and produce offspring. It may be because of any of the following mentioned reasons – abnormal spermatogenesis, incomplete maturation of the spermatozoa, abnormality in accessory organs’ patency, production of an inadequate volume of seminal fluid, inability to deposit the semen into the vagina, immobility of the spermatozoa adequate to reach the oocyte and penetrate it.

 

Female infertility

 

The major causes underlying female infertility are polycystic ovary syndrome (PCOS), premature ovarian failure (POF) and recurrent pregnancy loss (RPL).

 

Normally, there are three population growth patterns that are described –

 

1.       Positive growth

 

A population is said to have positive growth denote when the number of individuals in the older age group is less than the crude birth rate in either sex. Therefore, the population pyramid is broadest at the base and tapers at its top (Figure2).

 

a.       Rapid Growth

Rapid growth is denoted when the population size expands at a very high rate. The birth rate is much higher that the mortality rate in higher ages. Therefore, the pyramid becomes very steep. Such a positive rapid growth generally happens in rural populations where the family planning is least (Figure2). Example – Rapid population growth in Africa

 

b.   Slow growth

Slow positive population growth is when the population size increases in adequacy to the mortality rate in higher age. In such populations, the growth pyramid tapers gradually on the top. Such a population growth is generally seen in developed countries (Figure2). Example – Population growth in United States.

 

2.       Zero growth

 

Zero natural population growth is seen in populations where the birth rate almost equals the mortality rate. Such populations seem to have balanced growth. Example – Population growth in Russia.

 

3.       Negative growth

 

Negative population growth is seen in populations when the crude birth rate decreases than the mortality rate in older ages. In such populations, the population pyramid is narrowest at its base and broadens at its top or in middle (Figure3). Example – Negative population growth in Maltese Islands. The population growth of Malta is expected to decrease by 25% till 2025 (Figure4). The population pyramid for the Maltese Islands indicate a rapidly ageing population, which is projected to decline further at a higher rate between 2025 and 2050 (Figure3 and Figure4). Each pyramid hints towards the transitional phases that each age-cohort will undergo- a) rapid decline in births and a corresponding decline in children of younger age, b) a decline in the working-age population i.e. younger adults and older adults and c) a rapid increase in the older age groups or the dependent age group, especially the old female age group (75+ years).

Figure2. Patterns of population growth (Source:

http://sasmoodle.sd83.bc.ca/pluginfile.php/9788/mod_resource/content/1/Socials11New/c11/cda_py

ramidref.html)

 

Figure3. Population pyramid showing negative population growth in Malta

(Source: US Census Bureau, International Database)

Figure4. Expected negative population growth of Malta by 2025.

(Source: US Census Bureau, International Database)

 

Infertility as cause of negative or zero population growth

 

Infertility is one of the reason for the negative or zero population growth. Negative or zero population growth may not be a result of high mortality rate but lower birth rate. The lower birth rate may be determined by family planning measure or lower socio-economic growth or could be because of lower fertility rate. Infertility is one of the contributing factors for lower fertility rate.

 

Summary

  • Fertility if one of the demographic component of the population growth.
  • There are biological, socio-cultural and behavioral determinants of fertility.
  • Biological determinants of fertility include age and physiological inability.
  • Socio-cultural determinants of fertility include poverty or socio-economic status and family beliefs and pressure.
  • Behavioral determinants of fertility include stress, depression, anxiety etc.
  • Types of infertility are – primary infertility and secondary infertility.
  • Population growth patterns are affected by infertility
  • Positive population growth occurs when birth rate increases the mortality rate.
  • Negative population growth occurs when birth rate becomes lower than the mortality rate.
  • Increasing higher prevalence of infertility indicate a zero or negative population growth.
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    Glossary

 

Behavioral determinants of fertility – include stress, anxiety, depression.

 

Biological determinants of fertility – include age and physiological abnormalities.

 

Calculation of infertility – The percent of women who seek a child and as the percent of all women of reproductive age.

 

Fertility Determinants – Factors that determine the rate of fertility.

 

Infertility – a disease of the reproductive system defined by the failure to achieve a clinical pregnancy after 12 months or more of regular unprotected sexual intercourse.

 

Negative population growth – When the birth rate is lower than the mortality rate in higher ages.

 

Population pyramid – A graphical representation of the age and sex distribution of a population. Numbers or proportions of males and females in each age group are plotted as horizontal bars with the males on the left and females on the right. Pyramids may be constructed to show single years of age or, as with the IDB pyramids, 5-year age groups.

 

Positive population growth – When birth rate is higher than the mortality rate in higher ages.

 

Primary infertility – Occurs due to non-production of gametes in the body or improper functioning of accessory reproductive organs.

 

Secondary infertility – Occurs due to complications or inability to produce offspring after the first delivery.

 

Socio-cultural determinants of fertility – include socio-economic status and societal pressure.

 

Zero population growth – When the birth rate is almost equal to the mortality rate.

 

REFERENCES

  • Mascarenhas, M. N., Flaxman, S. R., Boerma, T., Vanderpoel, S., & Stevens, G. A. (2012). National, regional, and global trends in infertility prevalence since 1990: a systematic analysis of 277 health surveys. PLoS medicine, 9(12), e1001356.
  • Kara, E., & Simoni, M. (2010). Genetic screening for infertility: When should it be done?. Middle East Fertility Society Journal, 15(3), 139-145.

    WEB REFERNCES

  • http://sasmoodle.sd83.bc.ca/pluginfile.php/9788/mod_resource/content/1/Socials11New/c11/cd a_pyramidref.html
  • https://www.census.gov/population/international/data/idb/informationGateway.php

    SUGGESTED READING

  • WHO report, 2009- Prevalence of infertility.
  • Jean-Pierre Geungant – The proximate determinants during the fertility transition.
  • Brander, J. A., & Dowrick, S. (1994). The role of fertility and population in economic growth. Journal of Population Economics, 7(1), 1-25.
  • Short, R. V. (2001). Opinion: The future fertility of mankind: effects on world population growth and migration. Reproduction, Fertility and Development, 13(6), 405-410.