31880
Autism and Prematurity: Sharp Increase in Risk Correlates with Shorter Preganancy
Prematurity was identified as one of the risk factors of Autism Spectrum Disorder (ASD).
Objectives: to identify the correlation between prematurity level and ASD, in a cohort of children born prematurely in Israel and followed prospectively at one tertiary center.
Methods:
Retrospective analysis of the database recorded all of children born between 2011-2017 and followed at one tertiary prematurity clinic. The database was filtered for level of prematurity and subsequent diagnoses. Of interest was a diagnosis of ASD, however additional diagnoses were encountered.
Results:
Of the 416 children identified as born premature, 43 (10.3%) received a diagnosis or autism spectrum disorder. Birth week and subsequent diagnosis of ASD were compared. There was a linear correlation between the degree of prematurity and the risk of ASD with higher incidence in more extreme prematurity. Additionally, there was a significant difference between birth week of multiple pregnancies versus singletons.
When divided by gender, 246 (59.1%) were male, and 170 (40.9%) were female. Of 43 children bearing a diagnosis of ASD, 27 were males (11% of males) and 16 were females (9.4%) , which results in an almost 1:1 ratio of ASD in boys and girls, a different male to female ratio as recognized in "idiopathic" ASD. Additionally, 177 (42.5%) of the premature children were twins, and 7 (1.7%) were triplets. With an age range from 2-14.2 years old, the average age was 4.2 years with a standard deviation of 2 years. Birth week ranged from week 24 to 36+ 6days, with an average of 30.8 and standard deviation 3.3 weeks. Birth weight ranged from 368-3550 grams, with an average of 1427 g and standard deviation of 557 grams. In terms of additional diagnosis, of the 416 children, , 62 (14.9%) received a diagnosis of cerebral palsy, and 68 (16.3%) received a diagnosis of global developmental delay.
Conclusions:
In this study examining the correlation between autism and prematurity in Israel, we found a much higher prevalence—10.3%—of ASD in the premature population, compared to the known general incidence of 1.2%. The study also looked at birth week and birth weight, as well as a number of other factors. Of significance is that the earlier the babies were born (i.e. if they were born in week 27 of a pregnancy versus week 32), there was a statistically significant increase in autism rates. Additional findings of comparable rates in males and females support the theory that ASD in prematurity is linked to insult due to immaturity than to a genetic predisposition, which renders a much higher ASD rate in males (4:1). Since the diagnosis of ASD is commonly decided around the age of two years, it is possible that the actual incidence is even higher. Since early intervention has been shown to have significant impact on the prognosis and functioning of children with autism, it is important to be aware of prematurity as a significant risk factor, and to include ASD screening in each follow up of infants born before term.