4.2 Proximate determinants of fertility

Fertility is shaped by key biological and behavioral factors known as proximate determinants. These include marriage patterns, contraceptive use, induced abortion, and postpartum infecundability. Understanding these determinants helps explain fertility differences across populations and time.

The relative importance of proximate determinants varies based on cultural, socioeconomic, and policy factors. In low-contraception settings, marriage and breastfeeding patterns play a bigger role. As contraceptive use increases, it becomes the dominant factor influencing fertility levels.

Proximate Determinants of Fertility

Key Proximate Determinants

Top images from around the web for Key Proximate Determinants

• 

  18.11 Contraception – Human Biology View original

  Is this image relevant?

• 

  Frontiers | Women's education, contraception use, and high-risk fertility behavior: A cross ... View original

  Is this image relevant?

• 

  Frontiers | From Sperm Motility to Sperm-Borne microRNA Signatures: New Approaches to Predict ... View original

  Is this image relevant?

• 

  18.11 Contraception – Human Biology View original

  Is this image relevant?

• 

  Frontiers | Women's education, contraception use, and high-risk fertility behavior: A cross ... View original

  Is this image relevant?

1 of 3

Top images from around the web for Key Proximate Determinants

• 

  18.11 Contraception – Human Biology View original

  Is this image relevant?

• 

  Frontiers | Women's education, contraception use, and high-risk fertility behavior: A cross ... View original

  Is this image relevant?

• 

  Frontiers | From Sperm Motility to Sperm-Borne microRNA Signatures: New Approaches to Predict ... View original

  Is this image relevant?

• 

  18.11 Contraception – Human Biology View original

  Is this image relevant?

• 

  Frontiers | Women's education, contraception use, and high-risk fertility behavior: A cross ... View original

  Is this image relevant?

1 of 3

• Biological and behavioral factors directly influence likelihood of conception and successful childbearing
• John Bongaarts identified primary proximate determinants:
  • Proportion of women married or in sexual unions
  • Prevalence of contraceptive use
  • Incidence of induced abortion
  • Postpartum infecundability (primarily due to breastfeeding)
• Other proximate determinants include:
  • Frequency of sexual intercourse
  • Sterility
  • Spontaneous intrauterine mortality
  • Duration of fertile period

Factors Affecting Proximate Determinants

• Cultural, socioeconomic, and policy factors influence relative importance of each proximate determinant across populations and over time
• In populations with low contraceptive use, marriage patterns and postpartum infecundability tend to be primary determinants of fertility levels
• As contraceptive prevalence increases, it typically becomes dominant proximate determinant while relative importance of other factors diminishes
• In low fertility settings, further reductions may depend more on factors such as timing of childbearing and prevalence of secondary infertility
• Significance of induced abortion as proximate determinant varies widely depending on legal status, accessibility, and cultural acceptability of abortion services (e.g., more significant impact in countries with restrictive abortion laws)
• Relative importance of proximate determinants can differ between subpopulations within a country (urban vs. rural residents, different socioeconomic groups)

Influence of Proximate Determinants on Fertility

Marriage and Sexual Union Formation

• Marriage or sexual union formation patterns affect fertility by determining proportion of women at risk of childbearing
• Earlier and more universal marriage typically leads to higher fertility (e.g., in societies where marriage occurs in late teens or early 20s)
• Delayed marriage or non-marriage reduces fertility by decreasing exposure to regular sexual activity during most fecund years
• Proportion of women never marrying and age at first marriage are key factors influencing fertility levels

Contraceptive Use

• Contraceptive use reduces fertility by preventing conception
• Effectiveness, consistency, and prevalence of contraceptive use all impact fertility levels
• Highly effective methods (sterilization, long-acting reversible contraceptives) have greater fertility-reducing effect than less effective methods (barrier methods, traditional methods)
• Consistent and correct use of contraceptives is necessary for maximum effectiveness in preventing pregnancy
• Higher prevalence of contraceptive use in a population leads to lower fertility levels, assuming other proximate determinants remain constant

Induced Abortion

• Induced abortion reduces fertility by terminating pregnancies that would otherwise result in live births
• Incidence and accessibility of abortion services influence its impact on fertility
• In settings with restrictive abortion laws or limited access to safe services, women may resort to unsafe or illegal procedures, increasing health risks
• Where abortion is legal and widely available, it can serve as a means of fertility control and reduce unwanted births
• Abortion can be used to space births, limit family size, or terminate pregnancies resulting from contraceptive failure or inconsistent use

Postpartum Infecundability

• Postpartum infecundability, primarily due to breastfeeding, reduces fertility by increasing time between births
• Longer durations and higher intensity of breastfeeding extend postpartum infecundability
• Lactational amenorrhea (absence of menstruation during breastfeeding) suppresses ovulation, providing temporary contraceptive effect
• Breastfeeding practices vary widely across cultures and can significantly influence birth spacing and overall fertility levels
• Exclusive breastfeeding provides greatest fertility-reducing effect, while supplemental feeding or early weaning reduce postpartum infecundability

Interactions of Proximate Determinants

Synergistic and Counteracting Effects

• Proximate determinants can have synergistic or counteracting effects on fertility, depending on their interactions
• Fertility-reducing effect of contraceptive use may be partially offset by shorter duration of postpartum infecundability if breastfeeding is less common among contraceptive users
• Impact of induced abortion on fertility depends on prevalence of contraceptive use
  • In settings with low contraceptive prevalence, abortion may play more significant role in reducing fertility
  • Where contraceptive use is high, abortion may primarily serve as backup method for contraceptive failure
• Effect of marriage patterns on fertility is moderated by prevalence of contraceptive use within marriage
  • Later marriage has weaker fertility-reducing effect if contraceptive use is low among married couples
  • Delayed marriage combined with high contraceptive prevalence can lead to very low fertility levels

Direct Influence Between Proximate Determinants

• Proximate determinants can influence each other directly
• Prolonged breastfeeding may reduce frequency of sexual intercourse, further extending postpartum infecundability
• Postpartum abstinence (avoidance of sexual intercourse after childbirth) practices in some cultures can also extend postpartum infecundability
• Contraceptive use may lead to reduced duration or intensity of breastfeeding, as women may perceive less need for lactational amenorrhea
• Accessibility of induced abortion services may influence contraceptive use, as women may rely on abortion as a backup method if contraception is not consistently used or fails

Importance of Proximate Determinants in Context

Variations Across Populations and Time

• Relative importance of each proximate determinant varies across populations and over time
• Cultural factors influence marriage patterns, breastfeeding practices, and attitudes towards fertility control methods
• Socioeconomic factors, such as education and women's employment, can affect age at marriage, contraceptive use, and desire for smaller families
• Policy factors, including family planning programs and abortion laws, shape accessibility and acceptability of fertility control methods
• As societies undergo demographic transitions, the relative importance of proximate determinants typically shifts from marriage patterns and postpartum infecundability to contraceptive use

Differences Within Populations

• Relative importance of proximate determinants can differ between subpopulations within a country
• Urban residents often have lower fertility than rural residents due to factors such as later marriage, higher contraceptive use, and greater access to induced abortion
• Socioeconomic status influences fertility through pathways such as education, employment opportunities, and access to health services
  • Higher socioeconomic groups tend to have lower fertility due to delayed marriage, greater contraceptive use, and smaller desired family sizes
  • Lower socioeconomic groups may face barriers to accessing family planning services and may have higher fertility as a result
• Ethnic, religious, or regional subpopulations within a country may have distinct fertility patterns influenced by cultural norms and socioeconomic conditions