By Kavita Dehalwar
I. What is fertility?
Fertility Referring to the real reproductive performance of an individual, a couple, a group or a population. It is a demographic concept that quantifies the frequency of childbirth in a population over time.
II fertility trends
Definition::
Fertility trends refer to changes in fertility rates over time, influenced by social, economic, biological and political factors.
World models::
- Fertility decrease In developed countries due to urbanization, higher education levels, career orientation and access to contraceptives.
- Higher fertility In developing regions due to early marriage, lower education, cultural standards and limited family planning.
III. Fertility and social behavior
Social factors affecting fertility::
- Wedding diagrams: Early and universal marriage often leads to higher fertility.
- Level of education: Higher female education is associated with lower fertility.
- Job: Working women tend to delay childbirth or have fewer children.
- Cultural standards: Beliefs on the size of the ideal family, gender roles and fertility influence fertility.
- Religion: Some religious doctrines encourage higher fertility.
IV. Fertility and biological behavior
Biological factors influencing fertility::
- Age of women: Fertility culminates in the 1920s and decreased after 35.
- Health and nutrition: Poor health reduces fertility.
- Infertility: Biological infertility (in one or the other partner) limits the reproductive results.
- Menstrual and ovulation cycles: Timing affects the probability of design.
- Postpartum and lactation amenorrhea: These naturally remove ovulation and reduce birth intervals.
V. Differential fertility
Differential fertility Refers to variations in fertility between different population subgroups. These differences can be due to:
1 and 1 Ethnic groups::
- Cultural values and traditions around the size of the family vary.
- For example, in multiethnic countries, an ethnic group can present higher fertility rates than the others.
2 Socio-economic groups::
- Low -income groups can have higher fertility due to less contraceptive use and higher infant mortality.
- Righter, urban and more educated groups tend to have fewer children.
3 and 3 Mobility and migration::
- Migrants can initially maintain high fertility, but adopt the standards of the host country over time.
- Mobile populations may have reduced reproductive health care access.
4 Location (urban vs rural)::
- Urban residents generally have fewer children due to better education, health care and employment possibilities.
- Rural areas can show higher fertility due to the needs of agricultural labor and lower access to contraception.
VI. Fertility measures
Fertility is quantified using several statistical indicators. Here is the Main fertility measures with formulas and explanations::
1. Gross birth rate (CBR)
Definition::
Total number of living births for 1,000 people in a given year.
Formula::
Example::
If there are 20,000 living births in a population of 1,000,000: CBR =?
Boundaries::
- Not specific to age.
- Understands the total population, even those that are not of childbearing age.
2. Age specific fertility rate (ASFR)
Definition::
Number of births for 1,000 women in a specific age group (generally 5 -year intervals).
Formula::
Example::
If women aged 25 to 29 have 3,000 births and their population is 100,000: ASFR25-29 =?
3. Total fertility rate (TFR)
Definition::
Average number of children that a woman would have during her years of reproduction (generally 15 to 49 years), on the basis of current ASFRs.
Formula::
- The sum is on all reproductive age groups.
- The age interval is generally 5 years.
Example::
If the ASFR increases up to 600 in all age groups: TFR = 600 × 51,000 = 3.0 children per Womantfr =?
Interpretation::
- TFR 2.1 is considered the Replacement fertility (in developed countries).
- TFR> 2.1 = population growth; TFR <2.1 = lower population (without migration).
4. Net reproduction rate (NRR)
Definition::
Average number of girls that a woman would have during her lifetime if she was subject to specific fertility and mortality rates in current age.
Formula::
- NRR focuses on childrenBecause only they can reproduce.
Interpretation::
- NRR = 1 → Each woman is replaced by a girl → Stable population.
- NRR> 1 → The population increases.
- NRR <1 → declining the population (without migration).
VII. Summary Table of fertility measures
| Measure | Formula | Unit | To use |
|---|---|---|---|
| Gross birth rate (CBR) | |
For 1,000 inhabitants | General fertility indicator |
| Age specific fertility rate (ASFR) | |
For 1,000 women (age group) | Detailed analysis of fertility between age groups |
| Total fertility rate (TFR) | |
Children by woman | Better measurement of fertility potential |
| Net reproduction rate (NRR) | |
Girls per woman | Replacement of the population representing mortality |
VIII. Conclusion
Fertility is influenced by complex social, economic, cultural and biological factors. Understand fertility measures as Cbr,, Asfr,, TfrAnd RRN is essential for demographic policy, health care planning and socio-economic development. Differential fertility through Ethnic, regional and economic lines highlights the need for targeted interventions.
References
De Bruijn, BJ and de Bruijn, BJ (2006). Fertility: theories, frames, models, concepts (pp. 549-569). n / A.
Kumar, G., Vyas, S., Sharma, SN and Dehalwar, K. (2025). Urban growth prediction using a Ca-Ann model and a spatial analysis for planning policy in Indore City, India. Geojournal,, 90(3), 139.
McNicoll, G. (1980). Institutional determinants of the change of fertility. Population and Development Review441-462.
Morgan, SP and Hagewen, KJ (2005). Fertility. In Population manual (pp. 229-249). Boston, MA: Springer US.
Whelpton, PK and Kiser, CV (1945). Trends, determinants and control of human fertility. The Annals of the American Academy of Political and Social Science,, 237(1), 112-122.