MULTIPLE BIRTHS IN AUSTRALIA, 1944-63

From statistics on Australian confinements during the period 1944–63 it seems that the following conclusions can legitimately be drawn: (1) The proportion of multiple births increases with increasing age of mother up to about age 37, turns, and decreases thereafter. (2) The proportion of multiple births increases with increasing age of father up to about age 34–38 and is fairly constant thereafter. (3) The variation with age of father, however, only arises because of the high correlation with age of mother which is the determining factor. (4) The proportion of multiple confinements increases with birth order. This effect holds for all ages of mother except those over 40 where there is no significant variation. (5) The proportion of multiple confinements decreases from the first year of marriage to the second, then increases steadily to a maximum after about 15 years of marriage and then decreases slightly. (6) The proportion of binovular twins increases steadily with increasing age of mother up to about age 37, turns, and thereafter decreases steadily. (7) The proportion of monovular twins increases slightly with increasing age of mother up to about age 37 and is fairly constant thereafter. (8) From the small amount of data it appears that the proportion of triplets also increases with increasing age of mother. © 1969, Cambridge University Press. All rights reserved.