NEW YORK (Reuters Health) - A new study
suggests that kids who are born only a year or
two after an older sibling might be more likely to
be diagnosed with autism than those with a
bigger age gap.
Of all second siblings whose mothers became
pregnant with them less than a year after giving
birth to the older sibling, about 7.5 in every
1,000 were diagnosed with autism. When
mothers became pregnant three years or more
after giving birth, about 2.5 out of every 1,000
younger siblings were diagnosed with autism.
Rates were somewhere in the middle for
mothers who became pregnant between one
and three years after giving birth to their first kid.
But the authors of the research, published today
in Pediatrics, say they don't know if younger
siblings of closely spaced pairs are actually more
likely to have autism. It could also be that
parents can more easily recognize warning signs
of autism when they have more recently
watched another kid pass through
developmental stages, the researchers say.
"There's one possible explanation, (which) is that
there is some biological factor" such as a
mother's nutrient levels or stress that makes a
second child more at risk for autism when
siblings are closely spaced, Dr. Keely Cheslack-
Postava, the study's lead author, from Columbia
University, told Reuters Health.
Another explanation "is just better diagnosis and
better picking up on symptoms," Cheslack-
Postava said, "in which case it would be an
advantage to be more closely spaced."
According to estimates by the Centers for
Disease Control and Prevention, slightly less than
one percent of kids in America have autism.
Researchers have not identified a clear cause, but
some think it might be linked to conditions in the
womb - which could be different depending on
how closely siblings are spaced.
Cheslack-Postava and her colleagues used
California birth records to find all pairs of first and
second full siblings born in the state between
1992 and 2002. Combining that with information
on all autism diagnoses from the California
Department of Developmental Services, they
were able to match up in which sibling pairs
one, both, or neither child was diagnosed with
autism.
Because they were interested in the impact of the
length between pregnancies on autism, the
researchers focused on tracking second siblings
that were born with or without autism following
a first sibling that didn't have the condition. Out
of more than 600,000 pairs of siblings in which
the older sibling didn't have autism, about 3,000
younger siblings were diagnosed with autism.
When the authors controlled for certain
characteristics that may affect the risk of autism -
including the mother's age and race, and the
child's gender and birth year - the pattern of
spacing and autism rates remained the same.
The study does not prove that spacing children
closer together causes autism in the second
sibling, and Cheslack-Postava said there are
many possible ways to explain the link - and that
she "can't speculate as to what's the most likely."
One possible explanation is that mothers who
got pregnant soon after giving birth the first time
had low levels of certain nutrients like iron and
folate, or that their bodies were still under stress
from the first pregnancy, and that affected the
second child's development.
While it could also be that something about
parents who choose to have children close
together - such as their genes or hormones -
makes them more likely to have kids with
autism, the authors say this is probably not the
case. If it were, firstborn children in closely
spaced sibling pairs would also be more likely to
have autism, but that pattern didn't turn up in
the results.
The trend could, however, be explained by social
factors, Cheslack-Postava said. Parents may be
more likely to take a younger sibling to the
doctor to be checked out for autism if they
remember that only a year or two ago, when
their older sibling was the same age, he or she
was much farther along in development in
certain areas.
If that were true, some younger siblings in pairs
who were spaced far apart might not have been
diagnosed yet by the time the researchers
collected the study data.
Future studies will need to look more closely at
specific factors that could explain the link
between close pregnancy spacing and autism
risk, Cheslack-Postava said. For now, it's too
early to make recommendations to parents
about how to space their children if they are
trying to minimize the chance that a child will
have autism, she said.
"There are a number of reasons for why people
would choose to have children closer together
or farther apart," Cheslack-Postava said. "It's a
very individual decision including many factors."
And the findings, she said, shouldn't have any
impact on that decision.
Source: http://us.mobile.reuters.com/article/idUSTRE7091HQ20110110?ca=rdt
suggests that kids who are born only a year or
two after an older sibling might be more likely to
be diagnosed with autism than those with a
bigger age gap.
Of all second siblings whose mothers became
pregnant with them less than a year after giving
birth to the older sibling, about 7.5 in every
1,000 were diagnosed with autism. When
mothers became pregnant three years or more
after giving birth, about 2.5 out of every 1,000
younger siblings were diagnosed with autism.
Rates were somewhere in the middle for
mothers who became pregnant between one
and three years after giving birth to their first kid.
But the authors of the research, published today
in Pediatrics, say they don't know if younger
siblings of closely spaced pairs are actually more
likely to have autism. It could also be that
parents can more easily recognize warning signs
of autism when they have more recently
watched another kid pass through
developmental stages, the researchers say.
"There's one possible explanation, (which) is that
there is some biological factor" such as a
mother's nutrient levels or stress that makes a
second child more at risk for autism when
siblings are closely spaced, Dr. Keely Cheslack-
Postava, the study's lead author, from Columbia
University, told Reuters Health.
Another explanation "is just better diagnosis and
better picking up on symptoms," Cheslack-
Postava said, "in which case it would be an
advantage to be more closely spaced."
According to estimates by the Centers for
Disease Control and Prevention, slightly less than
one percent of kids in America have autism.
Researchers have not identified a clear cause, but
some think it might be linked to conditions in the
womb - which could be different depending on
how closely siblings are spaced.
Cheslack-Postava and her colleagues used
California birth records to find all pairs of first and
second full siblings born in the state between
1992 and 2002. Combining that with information
on all autism diagnoses from the California
Department of Developmental Services, they
were able to match up in which sibling pairs
one, both, or neither child was diagnosed with
autism.
Because they were interested in the impact of the
length between pregnancies on autism, the
researchers focused on tracking second siblings
that were born with or without autism following
a first sibling that didn't have the condition. Out
of more than 600,000 pairs of siblings in which
the older sibling didn't have autism, about 3,000
younger siblings were diagnosed with autism.
When the authors controlled for certain
characteristics that may affect the risk of autism -
including the mother's age and race, and the
child's gender and birth year - the pattern of
spacing and autism rates remained the same.
The study does not prove that spacing children
closer together causes autism in the second
sibling, and Cheslack-Postava said there are
many possible ways to explain the link - and that
she "can't speculate as to what's the most likely."
One possible explanation is that mothers who
got pregnant soon after giving birth the first time
had low levels of certain nutrients like iron and
folate, or that their bodies were still under stress
from the first pregnancy, and that affected the
second child's development.
While it could also be that something about
parents who choose to have children close
together - such as their genes or hormones -
makes them more likely to have kids with
autism, the authors say this is probably not the
case. If it were, firstborn children in closely
spaced sibling pairs would also be more likely to
have autism, but that pattern didn't turn up in
the results.
The trend could, however, be explained by social
factors, Cheslack-Postava said. Parents may be
more likely to take a younger sibling to the
doctor to be checked out for autism if they
remember that only a year or two ago, when
their older sibling was the same age, he or she
was much farther along in development in
certain areas.
If that were true, some younger siblings in pairs
who were spaced far apart might not have been
diagnosed yet by the time the researchers
collected the study data.
Future studies will need to look more closely at
specific factors that could explain the link
between close pregnancy spacing and autism
risk, Cheslack-Postava said. For now, it's too
early to make recommendations to parents
about how to space their children if they are
trying to minimize the chance that a child will
have autism, she said.
"There are a number of reasons for why people
would choose to have children closer together
or farther apart," Cheslack-Postava said. "It's a
very individual decision including many factors."
And the findings, she said, shouldn't have any
impact on that decision.
Source: http://us.mobile.reuters.com/article/idUSTRE7091HQ20110110?ca=rdt
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