According to the biggest study of fetal growth and autism to date published last month in the American Journal of Psychiatry, smaller babies and larger babies are at greater risk of autism. The study was conducted by the University of Manchester, England. The authors explored the associations between fetal growth, gestational age, and ASD with and without comorbid intellectual disability in a Scandinavian population.
This is the first study showing a distinct link between birth weight and the development of autism. It also supports a 2012 Northwestern University study suggesting a connection between low birth rate and autism in twins.
What the study found:
Babies who were born weighing 5.5 lbs. or less were 63% more likely to be diagnosed with autism later on while babies born weighing over 9 lbs. 14 oz. were 60% more likely to be diagnosed. The study also showed that preterm birth increased autism spectrum disorder (ASD) risk regardless of fetal growth. The same overall pattern was observed for ASD with and without intellectual disabilities. However, poor fetal growth (i.e., growth below the mean) was more strongly associated with ASD with intellectual disabilities than without.
What causes extreme developmental weight?
The authors of the study think that something is going wrong during development, possibly with the function of the placenta. A Yale School of Medicine study released last week suggests a newborn’s placenta can predict his or her risk for autism. The study found that placentas with abnormal folds or cell growths can increase the risk for autism.
Understanding the relationship between fetal growth and autism spectrum disorder is likely to advance the search for genetic and non-genetic causes of ASD.
What is Autism?
Autism is a general term for a group of complex disorders of brain development that can become obvious in communication and repetitive behavior. The onset of autism is generally within the first 3 years, and is obvious between 2 and 3 years of age.
How prevalent is autism?
The U.S. Centers for Disease Control and Prevention (CDC) classifies around 1 in 88 American children as on the autism spectrum–a ten-fold increase in frequency in 40 years. Research shows that this increase is only partly explained by improved diagnosis and awareness. Studies also show that autism is four to five times more common among boys than girls. An estimated 1 out of 54 boys and 1 in 252 girls are diagnosed with autism in the United States.
ASD affects over 2 million individuals in the U.S. and tens of millions worldwide. Also, government autism statistics suggest that prevalence rates have increased 10 to 17 percent annually in recent years. Although improved diagnosis and environmental influences are two reasons often considered, there is no established explanation for this continuing increase.
Women who are pregnant should discuss normal pregnancy weight gain with the physician or midwife at our office. As the article above indicates, extreme weight in newborns may be associated with problems originating in the placenta, which leads to a higher risk of autism.
Extremely low or high birth weight can present many other issues, some of which can affect a child for most if not all of their lives. But working with a good obstetrician or midwife can help you identify issues and address them early on if possible.
As more information about the role of the placenta in extreme weight in fetuses becomes available, we will post updates.
In the meantime, if you’re pregnant or planning to be pregnant, it’s important you at least speak with an obstetrician and midwife to ensure your baby is healthy – feel free to contact us with any questions, or schedule an appointment at All About Women’s Gainesville or Lake City office today.