Offspring of Men With Birth Defects Twice as Likely to Have Defects, Too
For Immediate Release
Tues., Feb. 13, 2001
NIEHS PR #01-05
Media Contact: Bill Grigg
(301) 402-3378, (301)496-3512
grigg at niehs.nih.gov
Men born with a birth defect have a substantially increased risk of
having a child with a birth defect, a large population study revealed
today. Compared with other fathers, the risk was doubled.
The second-generation risk also appeared higher - at least for
dissimilar birth defects - than for the offspring of mothers who had
been born with birth defects.
Scientists at the U.S. National Institute of Environmental Health
Sciences and Norway's University of Bergen reviewed Norwegian births
since 1967. They compared 12,000 men who had been born with a recognized
defect with nearly a half-million unaffected men. The scientists
reported today in the Journal of the American Medical Association for
Feb. 14 that the men had fathered 1,265 children and that:
Twenty-one of these children (1.6 percent) had been born with the same
defect as their father's. This is about seven times the risk of those
same defects in the general population but is about the same risk as a
previous study showed for the children of women with birth defects.
However, the children of fathers with birth defects also had a higher
risk of having different, unrelated birth defects. Forty-three children
(3.4 percent) had defects that were not like their father's, compared to
an expected number of 24 (1.9 percent). This result was in contrast to
the findings of the previous women's study in which the children of
women with defects appeared to have no increased risk of babies with
defects different from the mother's.
The total risk of birth defects was 5.1 percent among the offspring of
fathers with defects, or twice the 2.1 percent risk of the offspring of
other fathers. The risk was spread out across categories of defects, not
concentrated in any one category.
"Five percent of children with birth defects is not a whole lot," Allen
J. Wilcox, M.D., Ph.D., said, "but it still is more than double what we
see in the children of unaffected fathers." Dr. Wilcox is chief of
epidemiology at the National Institute of Environmental Health Sciences,
one of the U.S. National Institutes of Health.
"What surprised us," Dr. Wilcox continued, "is that the children of the
affected fathers had a higher risk of all kinds of defects, not just the
same defect as their father. In our earlier study of women with birth
defects, this did not appear to be the case: The children seemed to have
no special risk of birth defects except for the specific defect of the
Dr. Wilcox' co-researchers are Rolv T. Lie, Ph.D., and Rolv Skjaerven,
Ph.D., both professors at the University of Bergen. Their studies are
based on the Medical Birth Registry of Norway which links the birth
records of fathers, mothers and offspring through the Norwegian system
of unique personal identification numbers.
The investigators grouped the birth defects recorded into 24 categories.
Cleft lip, genitalia defects, limb defects and clubfoot (in which the
foot is twisted out of position) were the four most common recurring
defects that recurred in the offspring of affected fathers. In many
cases, these defects can be surgically repaired.
In their report, the three said they had expected an excess in defects
of the same type as the fathers because many birth defects are
heritable. They said they had no explanation for the increased rate of
In the study, boys with birth defects had a lower-than-normal survival
rate to age 20. Even if they survived to adulthood, they were 30 percent
less likely to father a child than other men. This pattern of reduced
reproduction (which the authors said presumably reflects social factors
as well as biological) had also been seen among affected women.
The scientists said the higher death rates among babies with birth
defects, as well as the reduced likelihood that the survivors will have
children, reduces the impact of parents with defects on the next
"We also need to put this into perspective," Dr. Wilcox said. "More than
95 percent of all babies with birth defects are born to parents who have
no known birth defects themselves. Measles, a lack of folate in the
diet, and heavy alcohol use are factors for some defects, but the causes
of most birth defects, environmental as well as genetic, are not known.
We have a lot to learn - still - about the cause and prevention of birth
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The URL for this press release is:
Gary N. Greenberg, MD MPH Sysop / Moderator Occ-Env-Med-L MailList
gary.greenberg at duke.edu Duke Occupat, Environ, Int & Fam Medicine
OEM-L Maillist Website: http://occhealthnews.com