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There are more than 100,000
multiple-birth children in Canada under 13 years of age and
41,000 multiple-birth children five years of age and under
each year.
More than 4,000 sets of
twins are born in Canada each year.
More than 75 sets of
triplets, quadruplets and quintuplets (combined) are born.
Multiple births in Canada
are on the rise: birth of twins has risen 35% (per 100,000
successful pregnancies) between 1974-1990.
The incidence of triplets
has increased almost 300% and quadruplets over 400% between
1974-1990.
Overall 15-17% of multiple
births result from infertility treatments.
It is estimated that 60% of
triplets, 90% of quadruplets and 99% of quintuplets result
from infertility treatments.
Incidence of twins is one
in 90 births (without fertility treatments).
Incidence of triplets is
one in 8,100 births (without fertility treatments).
Incidents of quadruplets is
one in 729,000 births (without fertility treatments).
Incidence of quintuplets is
one in 65,610,000 births (without fertility treatments).
Fraternal (dizygotic)
twins/triplets are the result of two/three fertilized eggs.
Family history, mother's
age, number of previous pregnancies, and race are
determining factors in the incidence of fraternal multiples.
Identical (monozygotic)
twins/triplets are the same sex, have the same blood types,
hair and eye color and chromosomes. They are a result of a
single egg splitting after conception. Environmental
influences can determine that characteristics such as
height, weight, ears, nose, lips are somewhat different.
Some monozygotic multiples are told they are fraternal (dizygotic)
- only DNA fingerprinting provides conclusive results.
Fraternal twinning does not
necessarily skip a generation.
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