BIBLIOGRAPHIC INPUT SHEET TEMPORARY Patterns of mortality ...

Chapter III, Birth-Weight
45
nonwhite populations in New York City in
1966. In the weight group of 1,000 grams
or less the percentages were 0.43 for white,
0.69 for Puerto Rican, and 1.54 for nonwhite.
Weights of 2,500 grams or less were
recorded for 7.9 per cent of live births in
the white group, 10.9 per cent in the Puerto
Rican, and 15.9 per cent in the nonwhite.
Thus there may be ethnic differences in the
weight distributions of live births, which in
turn may be due to differences in the health
condition of mothers. Ethnic differences as
well as their causative factors may be responsible
for some of the variations in the
distributions of neonatal and postneonatal
deaths by birth weight found in the Latin
American projects. No attempt was made
in this Investigation to obtain information
on ethnic groups, and this material for New
York City and for the United States is presented
principally to illustrate the many
factors that must be considered in the interpretation
of findings and also to stress
the value of collection of data on birth
weight in each country.
One of the reasons for including the project
in Bolivia was to study the relation of
altitude to birth weight. A longitudinal
study in the small community of Masma in
the Peruvian highlands (altitude 3,552
meters) revealed a higher frequency of lowweight
births and a lower mean birth weight
than in the coastal community of Lurin,
Peru (Deck, 1971). In the same country Mc-
Clung (1969) found that the infant in
Cuzco, at 11,000 feet, was more than 200
grams lighter than the infant born at sea
level (3,093 grams in Cuzco and 3,312 in
Lima). Lichty et al. (1957) reported on the
higher frequency of prematurity in Lake
County, Colorado, at an altitude of 10,000-
11,000 feet (30.8 per cent with birth weights
of 2,500 grams or less), than in the State of
Colorado as a whole (10.4 per cent) for the
five years 1949-1953. Such studies as these
suggested the probability of variations in
birth weight due to altitude.
At the Conference on Research Methodology
and Needs in Perinatal Studies, Te'­
ris (1966) reviewed the literature in his
report on the epidemiology of prematurity.
He summarized the studies on specific factors
related to prematurity such as illegitimacy,
prenatal care, and social class, reviewed
those concerning maternal nutrition,
and concluded that the relation between
maternal nutrition and prematurity remained
unsettled.
The data on birth weights in the projects,
as presented in this chapter (as well as in
others), are puzzling and yet indicate the
great potential value of such information.
Birth weight, as an important component
of the health condition of the child at birth,
should be obtained routinely as it determines
the chances of survival as well as the
management required in ternis of medical
care. In the collection of data of this type
the first requirement, if international conparisons
are desired, is to adhere to the
same definitions of a live birth and a fetal
death. If true and significant differences
are established, tile next step is exploration
in depth of the causes of such differences.
The size of the neonatal death rate depends
in large part on the frequency of lowweight
births. In 1960 when 24,323 births
with weights of 1,000 grams or less were
registered in the United States (Chase,
1969), 22,202 became neonatal deaths (or
91.3 per cent). In the next 500-gram group
(1,001-1,500) out of 27,756 births 14,475 (or
52.1 per cent) became neonatal deaths. In
all, 56,859 (72.7 per cent) of the neonatal
deaths were cf infants weighing 2,500 grams
or less, that is, immlature by the WHO definition.
Figure 25 shows the neonatal death
rate according to seven weight groups in