Bongaart's Proximate Determinats Of Fertility

In the year 1970, Bongaart refined the Davis and Blake's eleven intermediate variables of fertility into nine direct determinants of fertility called 'proximate determinats of fertility '. According to the Bongaarts, " the proximate determinants of fertility are the biological and behavioral factors through which social, economic and environmental 

variables affects fertility ".

The proximate determinants of fertility can be classified in two groups: 

1) Proximate Determinats Influencing Length of Reproductive Span

2) Proximate Determinats Influencing the rate of child-bearing within the Reproductive Span.

1) Proximate Determinats Influencing Length of Reproductive Span 

It includes the time period between first menstruation/ menarche and menopause. The menarche marks the beginning of the reproductive span or period and menopause marks the end of the reproductive period. It also includes marriage, divorce and separation, windowhood etc. which may have positive or negative impact in fertility. 

2) Proximate Determinats Influencing the rate of child bearing within the Reproductive Span 

Within the reproductive span, the married and fecund women reproduce at a rate inversely related to the average duration of the birth interval. Higher fertility is associated with short birth interval and lower fertility is associated with long birth intervals. The duration or length of her birth interval is determined by following components: 

1) Post-Partum infecundable period 

2) Conception Wait

3) Gestation period 

The above component of birth interval can be shown in the following diagram: 

a. Birth Interval without Intrauterine Death

b. Time Added by Intrauterine Death

1) The Post-Partum Infecundable Period

After the child-birth, a women passes through an infecundable period during which the normal pattern of ovulation and menstruation is absent, this is called Post-Partum infecundable period. The length of Post-Partum Infecundable period is primarily determined by the length of breastfeeding. With the increase in the duration of breastfeeding, the length of the amenorrhea period also increases which inturn increases the Post-Partum amenorrhea period. 

2) The waiting time to Conception 

This period which is also known as fecundable or ovulatory interval comprises the period from onset of ovulation after child-birth to conception. The length of this interval is determined by  natural fecundability and the use and effectiveness of contraception. Where  natural fertility is high and no use of contraceptive method is made the period of conception wait shorter. This period is lengthened with declining natural fertility and with higher practice and effectiveness of conception. 

3) Gestation period 

The period of full-term pregnancy doesnot vary much and its duration is assumed to be nine months. However, in case of pregnancy ends prematurely in a spontaneous or induced intrauterine death, the duration of the birth internal is lengthened by the additional components as plane B in the above figure.

Thus it is observed that the seven proximate determinants are:

1.Marriage

2. Onset of permanent sterility

3. Post-Partum in-fecundability 

4. Natural fecundability or frequency of intercourse

5. Use and effectiveness of contraception 

6. Spontaneous intrauterine mortality; and 

7. Induced abortion

 It is clear that the first two of these seven determinants determine the length of reproductive span and the other five determine the rate of child-bearing.