It is impossible to judge from statistics alone whether or not the work done by an individual woman, either her own housework or work for money, is so excessive as to affect her during pregnancy or while nursing to the extent of reacting on the health of the baby; but the fact is that the infant mortality rate is higher among the babies of wage-earning mothers than among others, being 188 as compared with a rate of 117.6 among the babies of nonwage-earning mothers. Wage-earning mothers and low-wage fathers are in practically the same groups, and it is difficult to secure an exact measurement of the comparative weight of the two factors in the production of a high infant mortality rate.

ILLEGITIMACY

Of the 1,551 birth included in this investigation 34, or 2.2 per cent., occurred out of wedlock. Nine of the 32 illegitimate babies who were born alive died during their first year. It is recognized that these figures are a very small base from which to draw conclusions concerning the effect of illegitimacy on the infant mortality rate. It is of interest, nevertheless, to note that the findings for this small group are similar to those of countries which compute an infant mortality rate for legitimate and illegitimate children separately, that is, a rate for illegitimates more than twice as high as for children born in wedlock.

Thirty-two, or 3.7 per cent., of the 860 native mothers, as compared with 2, or 0.3 per cent., of the 691 foreign mothers visited, had illegitimate children in 1911.

In addition to the data relating exclusively to babies born in 1911, a statement was secured from each mother as to the number and duration of each of her pregnancies and the result thereof; that is, the number of children she had borne, alive or dead, the number of miscarriages she had had, and the age at death of each live-born child who had died. Although this information was secured for all mothers, tabulations are presented of the data furnished by married mothers only. Comparatively few single mothers reported more than one child, and information from them on this point is not believed to be as reliable as that from married mothers.

The 1,491 married mothers of babies born in 1911 had had an aggregate of 5,554 pregnancies, resulting in 5,617 births, the excess of 63 births over pregnancies being due to plural births. Eight hundred and four of these children died under 1 year of age, making an infant mortality rate of 149.9 for all their babies, as compared with the rate of 134 for those born in 1911. The stillbirths of these women numbered 194, or 4.5 per cent. of the total number of births; miscarriages reported numbered 191, but these were not added to the total reportable^[36] pregnancies.

Details as to the infant mortality rates for all babies born to native and foreign mothers included in this study, not only in the year 1911 but at any other time, are presented in the next table, which classifies the babies according to the total number of reportable pregnancies that their mothers had had, to and including the pregnancy resulting in the 1911 birth.

The statistics, based upon the results of all her reportable pregnancies, show a generally higher infant mortality rate where the mother has had many pregnancies, but there is not always an increase from one pregnancy to the next. This is more clearly shown when the pregnancies are grouped as in the next table.

This tendency is shown in still another form of summary: Combinations of four or less pregnancies are, for convenience, considered as group 1, while the combinations of over four are designated group 2. The differences in rates in the two groups are notable. The infant mortality rate is much lower for the first than for the second group.

This influence of the size of the family upon the infant mortality rate is shown in the computations giving the relative infant mortality rate for the different children borne by married mothers. The rate is most favorable for the second-born child, being 131.2. Among first born it is 143.6; for tenth or later born children 252.3.

The next table gives a further elaboration of the same data; that is, it shows the infant mortality rate where such rates are lowest and highest, respectively, according to the age of the mother at the child’s birth and the order in which the child was born. Attention is again directed to the fact that the statistics presented in this section on “Reproductive histories” are based upon the total number of reportable pregnancies; that is, in addition to the pregnancies resulting in births in 1911, all prior pregnancies of the women considered in the investigation have been included.

The difference in size of family for native and foreign mothers of different ages are indicated in the next table. The total and average number of live-born children, not reportable pregnancies, are given.

The next table shows all losses of pregnancy sustained by 628 mothers and the rate of loss per 1,000 births for mothers having different numbers of births or reportable pregnancies. For all mothers it was 188.4. “Loss,” as here used, means the sum of infant deaths (or deaths in first year) and stillbirths.

The influence of the economic factor on infant mortality among the babies born prior to 1911 can not be determined with exactness, as no inquiry was made concerning earnings of the father when the other children were born. But it is believed that his earnings during the year following the birth of the 1911 baby can be regarded as an index of the economic standing of the family for some time past. In individual cases, of course, revolutionary changes in the family’s income may have occurred, but for the great mass of people in the group considered it is not likely that within such a short space of time as that covered by the child-bearing period of the women considered—most of whom had not had numerous pregnancies—marked changes had taken place. If these known earnings are accepted as an index, the following variations are found to occur in the infant mortality rate for all the babies of whom a record was secured:

The infant mortality rate for the babies whose fathers earn under $521 is almost twice as great as for those born into families in the most prosperous group. These figures strengthen the conclusion reached in the study of the babies born in 1911, namely that the economic factor is of far-reaching importance in determining the baby’s chance of life.