What are the Factors Affect Infant Mortality Rate?

A variety of factors affecting infant mortality are customarily classified as biological and socio-economic or environmental factors, though these two categories should not be treated as watertight compartments, for there is a great deal of interaction between the two.

At times, it is even possible to modify biological factors by introducing changes in socio-economic factors. For the sake of convenience, however, these two types of factors will be discussed separately.

As has been pointed out earlier, the recent spectacular decline in general mortality has affected all age groups to some extent, but the magnitude of the decline has varied at different ages.

The reduction in mortality was considerably greater in the younger age groups than in the older age groups. In general it may be said that the low level of infant mortality appears to be associated with the low level of general mortality.

The level of mortality is very high in the first few hours, days and weeks of life. The reasons for infant deaths at the earlier and later stages of infancy differ to a certain extent.

Hence, in a study of infant mortality, infant deaths are carefully grouped into two categories according to the age at death. The first category consists of those infants who die before they complete four weeks of life.

The other category consists of those infants who die between 28 days and 365 days of their life. The rate based on the first period is known as the neo-natal mortality rate, while that on the second period is referred to as the post-neo-natal mortality rate.

Factors which affect foetal and neo-natal deaths are primarily endogenous, while those which affect post-neo-natal deaths are primarily exogenous.

Endogenous Factors

The endogenous factors are related to the formation of the foetus in the womb and are, therefore, mainly biological in nature.

Among the biological factors affecting foetal and neo-natal infant mortality rates, the important ones are the age of the mother, the birth order, the period of spacing between births, prematurely, weight at birth and the fact of multiple births.

Of all the factors listed above, the following have been studied in great depth: the age of the mother, the parity of the mother and the order of pregnancy and or of birth.

It has been generally observed that foetal and neo-natal mortality rates are higher at the younger ages of the mother (that is, below the age of 19), at first parity and for the first birth order.

These mortality rates start declining up to the age of 29 of the mother and at the second and third parity and then again increase with higher age of the mother, higher parities, and high birth orders.

Thus, if a graph of foetal and neo-natal mortality rates is drawn with respect to these factors, it would more or less resemble a U-shaped curve.

The maturity of an infant at birth has also been found to be an important factor affecting neo-natal and infant mortality rates.

It has been observed that the weight of the baby at birth is also an important factor affecting neo-natal and post-neo-natal deaths. In the United States, it was observed that a low birth weight was the cause of two-thirds of all the neo-natal deaths in 1950.

It was also found that the chances of survival increased considerably with even a moderate increase in the birth weight the optimum birth weight ensuring survival being 3,501-4,000 gms.

It may be noted here that the still-birth rate and the neo-natal mortality rate are both very high in the case of multiple births.

It may be concluded from this discussion that the causes of foetal and neo-natal deaths so far considered arise mainly out of genetic factors, and may be traced back to the intrauterine life of the foetus and to the damage occurring during the process of birth.

Exogenous Causes

Social, cultural, economic and environmental factors are also found to affect infant mortality, especially during the post-neo-natal period.

Post-neo-natal deaths are therefore mainly due to various epidemics caused by communicable diseases, both of the digestive systems, such as diarrhea and enteritis, and of the respiratory system, such as bronchitis and pneumonia, as well as by faulty feeding patterns and poor hygiene.

The underlying environmental factors include crowding and congestion, in sanitary surroundings, lack of proper sunshine and fresh air, etc.

Illegitimacy is also an important factor contributing to a high infant mortality rate. The difference between infant mortality rates of legitimate and illegitimate births is usually found to be quite marked. The reason for this difference is quite obvious.

A child conceived and born out of wedlock is generally unwanted both by the mother as well as society. Consequently such a child does not receive the care, in terms of nutrition and other facilities that it needs.

One interesting feature of the role of endogenous and exogenous factors in determining infant mortality rates is worth noting.

In countries where infant mortality rates are very low, a higher proportion (that is, more than two-thirds) of infant deaths occurs during the neo-natal stage, because, being developed, they have been successful in almost completely eliminating the environmental factors responsible for such deaths.

The main causes of infant mortality in these countries are, therefore, mainly genetic or biological in nature. On the other hand, in countries where infant mortality rates are high, the majority of infant deaths occurs after the neo-natal stage and is due mainly to environmental factors.