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Flu during pregnancy linked with increased risk of autism

Autism Spectrum Disorders (ASD) appear to be an increasing medical issue in the United States. According to the Centers for Disease Control and Prevention, ASD is diagnosed in approximately 1 in 88 children, and are reported to occur in all racial, ethnic, and socioeconomic groups. ASD refers to a broad range of symptoms, from mild social awkwardness to mental retardation, repetitive behaviors and an inability to communicate. The CDC states that diagnosing ASD can be difficult, because there are no medical tests, such as a genetic or blood test, that can provide a definitive diagnosis. Physicians make a diagnosis through observation of a child’s behavior and development.

Medical science agrees that the increase in diagnosis is not only a result of better diagnostic standards, but also because there appears to be more children who are actually developing autism. Unfortunately, science has not uncovered the cause. Genetics are a critical factor, for example, since it has been shown that if one twin has autism there is a high likelihood that the other twin will also develop ASD. But are there other factors?

A study of 96,000 children in Denmark, published today in Pediatrics by Atladóttir et al., may provide a bit more information about the autism puzzle. The study included children who were born between 1997 and 2003, which is approximately 30 percent of all the women in Denmark who had children during those years. The women were interviewed twice while they were pregnant and then again when their babies were six months old. They were specifically asked about sicknesses they had, and about drugs they took to treat them. Among their offspring, 976 were diagnosed with autism spectrum disorder and 342 with infantile autism.

The research found that women who had the flu during pregnancy were twice as likely to have a child that will be eventually diagnosed with autism. Furthermore, those women who had a fever lasting longer than a week, caused by the flu or something else, were three times as likely to have an autistic child. The evidence from this study seems to be another piece of evidence that indicates that the mother’s immune system may have an effect on the developing fetal brain. Women who reported other infections, such as a cold, a urinary tract infection or herpes, were not more likely to have a child with autism. The study also did not suggest that the use of antibiotics during pregnancy were a risk factor for ASD.

The authors do note that, “we do not know whether a febrile episode in our study is acting as a proxy for a specific infectious illness, specific severity of illness, a specific immune response, or if the direct action of hyperthermia on the fetus is potentially harmful.” They also stated that, even though the results were statistically significant, there is a small (5%) possibility that the results could be “a coincidental finding.” Also, since this study was done through interviews and memory of events during pregnancy, the data could be considered somewhat unreliable.

However, these results support a study published in the Journal of Autism and Developmental Disorders by Zerbo et al. that also found that women in the United States who had fevers while pregnant were twice as likely to have a child with autism or a developmental disorder. According to a story in NBC News, Dr. Irva Hertz-Picciotto of Stanford University’s MIND Institute (a coauthor of the US based study), “growing evidence suggests inflammatory processes may be interfering with brain development at critical stages, leading to changes in behaviors  such as those associated with autism, as well as cognitive deficits.”

Dr. Coleen Boyle, Director of the National Center on Birth Defects and Developmental Disabilities at the Centers for Disease Control and Prevention, gave this statement to NBC News:

All women need to get their flu shots regardless of whether they are pregnant. And if a woman is pregnant and experiencing flu-like symptoms, she should call her doctor right away. If she has a fever, that fever can be treated with Tylenol. We know from other studies that fever (during pregnancy) can lead to other serious health problems in a child, such as a birth defect.

If these results continue to be supported by new research, then the flu vaccine may actually lower the risk of autism. As I reported previously, flu vaccines are safe during pregnancy, and it may actually have additional benefits like reduced miscarriages

 Vaccines Save Lives.

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