Abstract
In a preceding paper 1 evidences for the existence of a low positive correlation between the age of the parents and the length and weight of the newborn infant of various nationalities have been adduced. The present paper is devoted to a consideration of the relationship between pregnancy order and birth order on the one hand, and the length and weight of the infant on the other. The source of the data is the same as that of those employed in the preceding investigation.
By pregnancy order I understand merely the serial order of the pregnancy (Gravida). By birth order I understand merely the order of birth of the child (Para). These differ by the number of miscarriages which may have occurred previous to the birth under consideration.
In Diagram 1 and 2 the heavy bars in each of the four panels denote zero correlation, as shown on the scale of ordinates.
Examination of the correlations for pregnancy order and the lengths of boy and girl infants shows that in 9 of the 12 available series the coefficients are positive, whereas in 3 of the series they are negative in sign. For the relationship between pregnancy order and weight of child, all of the coefficients are positive in sign. Thus for both weight and length, 21 of the 24 coefficients indicate a positive correlation between pregnancy order and the weight or length of the child.
The average values of the coefficients measuring the relationship between pregnancy order and the characteristics of the child are:
Pregnancy order and length of son, $r = +.0914
Pregnancy order and length of daughter, $r = -.0117
Pregnancy order and weight of son, $r = +.2102
Pregnancy order and weight of daughter, $r = +.1393
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