Biological and socio-ecological factors influencing Fecundity, Fertility, Natality and Mortality


Natality is the birth rate, which is the ratio of total live births to total population in a particular area over a specified period of time;expressed as childbirths per 1000 people per year.


Fertility is generally used to indicate the actual reproductive performance of a women of groups of women.

Factors determining fertility.

The most basic concept is that the birth of a child is not possible unless…

1)sexual intercourse has occurred

2)intercourse has resulted in pregnancy

3)pregnancy has been brought to successful terms.

1.factors affecting exposure to intercourse:-

a. those governing the formation and dissolution of unions

in the reproductive period.

1.age of entry into sexual unions

2.permanent celebacy;proportion of women not entering

into sexual unions

3.amount of reproductive periods spent after or between


1.when unions are broken by divorce,separation or


2.when unions are broken by death of husbands.

b. those governing the exposure to intercourse within


a. voluntary abstinence

b. involuntary abstinence(from impotence,illness)

c. coital frequency(excluding periods of abstinence)

2.factors affecting exposures to conception:

d. fecundity or infecundity as affected by

involuntary causes.

e. use or non use of contraception

a. by mechenical or chemical means

b. by other means

f. fecundity or infecundity as affected by

voluntary causes. Sterilization etc.

3. factors affecting gestation and successful parturition:

g. fetal mortality(abortion) from involuntary


h. fetal mortality from voluntary causes.

Factors associated with long term decline in fertility in developed countries.

Motivational factors-over the years the attitude shift toward growing population has changed the thinking of couples. It has shifted a strong motivation towards limited family. All the forces of organised society- the Law,officialdom,the clergy,educators,writer,press were mobilized to prevent birth control from spreading.

Economic and social factors-these are some social and economic factors reviewed in the context of fertility decline-industrialization,urbanization,rising levels of living and increased coast of bringing up children,family functions and structure,relationship between mortality and fertility,social mobility.

Differential fertility.

It has been observed that the levels and patterns of fertility vary considerably in various sub groups of the same population. These sub groups may be based on residence , whether urban or rural, social and caste,race etc. a study of differential fertility is useful in identifying the factors which determine the fertility levels among various sub groups.

Differential fertility can be understood as a result of following factors.

Ecological factors

a)Regional differences in fertility-there is a great deal of variation in fertility among various states and union territory.

b)rural urban residence and fertility-it was found that the fertility of those residing in cities was lower than that of rural residence and these differentials were more or less stable. However when national birth rate declined these fertility differentials widened in a more pronounced manner among urban upper classes than among others. Rural urban differences narrowed down again when birth rates rose after the second world war.

Socio-economic factors

a)educational attainment and fertility-the educational attainment of couples has a very strong bearing on the number of children born. The higher the educational level the lower was the family size.

b)economic status and fertility-general studies in the past have highlighted the inverse relationship between the economic status of family and fertility. this traditional relationship is now undergoing substantial changes as far as the developed countries are concerned.

c)occupation of husband and fertility.

Occupation of husband is used as the indicator of social economic status,and differential fertility is studied according to the occupation of the husband. It was generally observed that the wives of those engaged in professional jobs had the lowest fertility.

d)employment of wife and fertility.

The gainfully employed women have a smaller number of children than those who are not employed.

e)religion,caste,race and fertility.

The injunctions laid down in various religion indicate the importance of high fertility.

Christian-be fruitful multiply and replenish the earth.

Islam-marry a women who holds her husband extremely dear and who is richly fruitful.

Hinduism-make the bride the mother of good and fortunate child bless her to get 10 children and make the husband the eleventh one.

It may however be noted that all these religions have their roots in distant past when mortality rate was high.

It was observed in india that muslims have a higher fertility rate than hindus and christian.

It was observed that upper caste hindu had on an average 3.8 live births while lower caste hindus have 4.1 births.

In the us the negroes show more fertility than the white ones.

Inter-relationship between socioeconomic variables affecting fertility.

When the husbands are highly educated, they tend to have educated wives. Higher educational levels are related to higher incomes and more gainful occupations leading to higher standards of life. In a community in which women are educated the influence of religious dogma is likely to be less rigid, while if community has a high proportion of illiterate women,religious influences tend to be strong and affect fertility. Age at marriage is also closely associated with the educational attainment of wives.


the study of mortality deals with the effects of death on the population. Death as defined is the permanent disappearance of all evidence of life at any time after birth has taken place.

Sex and age pattern of mortality

in most countries of the world the crude death rates as well as the age specific death rates are higher for males than females. There is a great deal of evidence to indicate that as far as mortality is concerned males are at a definite disadvantage.

infant mortality- it is the total number of child death per one thousand in a given year.

The trends in infant mortality rates of developed and developing countries indicate that some overlapping of these rates has occurred between these two regions. This phenomenon has raised an important issue regarding the utility of infant mortality rate as an indicator of social and economic development.

Factors affecting infant mortality rate-it is seen in two stages first in first 4 weeks called neo-natal mortality rate and second from 28 to 365 days is called post neo natal mortality rate. These are mainly described in as endogenic and exogenic causes.

The endogenous factors are related to the formation of the fetus in the womb and are therefore mainly biological in nature. Among the biological factors, important ones are the age of the mother,the birth order,the period of spacing between births, prematurity, weight at birth.

Social cultural and environmental factors are also found to affect infant mortality during post neo natal phase. Post neo-natal deaths are therefore mainly due to various epidemics caused by communicable disease both of the digestive system such as diarrhoea and enteritis and of respiratory system such as bronchitis and pneumonia. Unsanitary surroundings,low sunshine,fresh air.

Reasons for high mortality in the past.

1.acute and chronic food shortages, causing famines and conditions of malnutrition


3.recurrent wars.

4.poor sanitary conditions.

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