Human Fertility and its Determinants
Sopyan, S.Sos, MA.
National Population and Family Planning Board (BKKBN)
South Kalimantan
December 28, 2011
F ertility and Fecundity
• Fertility refers to the number of live births a woman has actually
had.
• Fecundity refers to physiologic al capacity to produce a live birt
h.
Some important concepts
• Marital fertility : the number of live births to married women
• Natural fertility : populations in whi ch no deliberate attempt is made to li mit the number of births
• Reproductive period : A woman’s reproductive period is from menarche to menopause (usually from age 15-49)
Approaches to fertility level study
• Period fertility : looks at fertility cross- sectionally, that is at births occurring duri
ng a specified period of time, normally oneyear.– Ratio of live birth that occur in a population
during one year period to the population that bears the child
• Cohort fertility : looks at fertility longit udinally, that is at all births occurring to a s
pecific group of women (e.g. all those born or married in particular period of time)
Some Problems in Measuring Fertility
• It is difficult to establish accurate stati stical records on live births, a child die
s before the birth is registered.• Fertility measurement is complicated
by the fact that fertility involves two parents.
• Not every woman is truly exposed to t he risk of childbearing.
Sources of data for Fertility Study
• Vital Statistics: Birth Registration• Census• Surveys
• Information on Fertility and it’s determinants usually collected through surveys
• The 1960s onwards saw many large scale international efforts to collect fertility data, ex. WFS (1974-1986), CPS (1977 – 1985), DHS (1984 – Present).
Basic fertility measurements
• Child/Women Ratio• Crude B irth R ate (CBR)• General Fertility Rate (GFR)• Age Specific Fertility Rate
(ASFR)• Total Fertility Rate (TFR)
Basic fertility measurement
•Child/Women Ratio
Children aged 0-4
-Womenaged1 5 4 4
Require few information, no data on births are needed
Sensitive to reporting error and infant mortality
Basic fertility measurement
•Crude birth rate (CBR)
•Why is it “crude” ? ...…..
Number of births in year
Population at mid yearX 1,000
Basic fertility measurement
•Age specific fertility rate (ASFR)
Births in year to women aged x
Women aged x at mid-year
X 1,000
Basic fertility measurement
Total fertility rate (TFR)– most widely used by demographer
– TFR : - The average number of live births of a woman (or group of women) during
her lifetime if she were to pass through her childbearing years conforming to th
e age specific fertility rate of a given year.
– Calculate by adding up ASFRs X 5
Cohort Measurement
Parity Progression Ratio (PPR)– The probability of having another
child given that one has already had a certain number.
– Women in older age group are usually chosen for calculating PPR.
Reproductivity
• Gross Reproduction Rate– Sum of ASFRs calculated for female
births only
• Net Reproduction Rate– A female born will only replace her
mother provided she live to the age of her mother as on the day that she was born.
Replacement level fertilty
• The level of fertility at which a couple has only enough children to replace themselves, or about two children per couple. – TFR = ?– GRR = ?– NRR = ?
Components of fertility
• Biological component– Fecundity : physiological
capacity to produce a live birth
• Social component– different fertility desire in
different society
Ovulation
Eggs released
Sexual Intercourse
Sperms released
Human reproduction
Egg fertilized by sperm
Conception
Implementation in uterus
Parturition Abortion
Nine months or 280 days
Gestation Period
Davis and Blake’s Intermediate Variables (1956)
In 1956 Davis and Blake proposed a framework for analyzing the bio-medical determinants of fertility. They identified 11 intermediate variables divided into three blocks.
• Direct effect on fertility• Social factors indirectly effect fertility throug
h the intermediate variables.• Each intermediate variable may have a nega
tive or positive effect on fertility.
To have a live birth, a woman passes t hrough three stages
• she has sexual intercourse (coitus)
• she become pregnant (conception)
• she successfully completes the period of pregnancy or gestatio
n and gives birth to the child(gestation)
Davis and Blake’s Intermediate Variables
• Intercourse variables– age of entry in sexual unions– permanent celibacy– amount of reproductive period spent aft
er or between unions– voluntary abstinence– involuntary abstinence (impotence, separation
etc)
– coital frequency
Davis and Blake’s Intermediate Variables
• Conception variables– fecundity or infecundity (involunt
ary causes e.g. post-partum amenorrhea)
– use or non use of contraception– fecundity or infecundity (voluntar
y causes e.g. sterilization)
Davis and Blake’s Intermediate Variables
• Gestation variables– Foetal mortality from involuntary
causes– Foetal mortality from voluntary c
auses
Bongaarts’ Proximate DeterminantsModel of Fertility Analysis
John Bongaarts refined the list of variables to eight proximate determinants
The model focuses on 4 of the proximate determinants. The TFR in any society is a function of the Total Fecundity of a population modified by the levels of the four intermediate variables.
TFR=Cm . Cc . Ci . Ca . TF• Proportion of women married or in sexual unions• use of birth control• breast feeding and lactational amenorrhoea• induced abortion
Family planning methods
• Modern methods– Female/male sterilisation– Pills – IUD– Injectables– Condom– Norplant
• Traditional methods– Rhythm– Withdrawal– Prolonged breast feeding
Class Exercise
Please answer the following questions.
• What is the current level of fertility in your province?
• What is the major proximate determinants operating to change fertility in your province? Provide reasons.
• What is major socio-economic variable responsible for changing levels of fertility in your province? Provide reasons.
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