Multiple birth frequency according to parity and maternal age.

Abstract

SUMMARYThe Author has examined the published statistics of multiple births in England and Wales 1938-45, in Italy 1948-49 and in New York 1936-37, to see to what extent the apparent increase in frequency of twin births as parity increases amongst mothers of a quinquennial age-group is exaggerated by the mere fact of grouping. He concludes that the effect of the 5 year grouping on the rates is small, and that the data from the three countries indicate that at certain ages the probability that a birth will be multiple tends to increase with the order of the birth.