Tuesday, July 12, 2011

Study : Perinatal and Neonatal Risk Factors for Autism

I thought this study was interesting in light of the recent twin study suggesting that the environment may play a role in developing autism.  The bottom line here seems to be that there isn't any known perinatal or neonatal factor that plays a large role in developing autism.

Perinatal and Neonatal Risk Factors for Autism: A Comprehensive Meta-Analysis
Hannah Gardener, ScD, Donna Spiegelman, ScD, Stephen L. Buka, ScD

Background: The etiology of autism is unknown, although perinatal and neonatal exposures have been the focus of epidemiologic research for over 40 years.

Objective: To provide the first review and meta-analysis of the association between perinatal and neonatal factors and autism risk.

Methods: PubMed, Embase, and PsycInfo databases were searched for studies that examined the association between perinatal and neonatal factors and autism through March 2007. Forty studies were eligible for the meta-analysis. For each exposure, a summary effect estimate was calculated using a random-effects model. Heterogeneity in effect estimates across studies was examined, and, if found, a meta-regression was conducted to identify measured methodological factors that could explain between-study variability.

Results: Over 60 perinatal and neonatal factors were examined. Factors associated with autism risk in the meta-analysis were abnormal presentation, umbilical-cord complications, fetal distress, birth injury or trauma, multiple birth, maternal hemorrhage, summer birth, low birth weight, small for gestational age, congenital malformation, low 5-minute Apgar score, feeding difficulties, meconium aspiration, neonatal anemia, ABO or Rh incompatibility, and hyperbilirubinemia. Factors not associated with autism risk included anesthesia, assisted vaginal delivery, postterm birth, high birth weight, and head circumference.



  1. The combined effects of the tetanus shot given to pregnant women – sometimes various shots and in some countries with thimerosal and with alum- the flu shot – given at any time in pregnancy-and medications used in delivery (terbutalin) and the immunoglobulin Rh coexposure- considering the confounders such as prenatal exposure to infections and prenatal vitamins as protectors- beyond the maternal/parental age should also be considered IMO in combined impact.
    The impact of the potential pertussis shot in pregnancy should be also included, especially with the impact that the DTwP has in the interleuquin 6 levels..
    Prenatal exposures to pesticides and other xenobiotics through food, prenatal exposures to paint or mold , air contamination impact, water quality (arsenic content for example) fungal- infections during pregnancy- besides bacterial or viral- and other conditions such as preeclampsy should also be analyzed- and they are not in a framework of combination of impacts.

    The preterm birth finding is surprising, especially with the amount of studies that correlate preterm birth and ASD. Probably the point is that the findings are correlated wtih extremely preterm children.
    J Pediatr. 2010 Apr;156(4):525-31.e2. Epub 2010 Jan 13.
    Autism spectrum disorders in extremely preterm children.
    Johnson S, Hollis C, Kochhar P, Hennessy E, Wolke D, Marlow N.
    OBJECTIVES: To investigate the prevalence, correlates, and antecedents of autism spectrum disorders (ASD) in extremely preterm children.

    STUDY DESIGN: We conducted a prospective study of all births <26 weeks gestation in the United Kingdom and Ireland in 1995. Of 307 survivors at 11 years, 219 (71%) were assessed and compared with 153 term-born classmates. Parents completed the Social Communication Questionnaire (SCQ) to assess autism spectrum symptoms, and ASD were diagnosed by using a psychiatric evaluation. An IQ test and clinical evaluation were also administered. Longitudinal outcome data were available for extremely preterm children.

    RESULTS: Extremely preterm children had significantly higher SCQ scores than classmates (mean difference, 4.6 points; 95% CI, 3.4-5.. Sixteen extremely preterm children (8%) were assigned an ASD diagnosis, compared with none of the classmates. By hospital discharge, male sex, lower gestation, vaginal breech delivery, abnormal cerebral ultrasound scanning results, and not having had breast milk were independently associated with autism spectrum symptoms. By 6 years, independent associates were cognitive impairment, inattention and peer problems, withdrawn behavior at 2.5 years, and not having had breast milk.

    CONCLUSIONS: Extremely preterm children are at increased risk for autism spectrum symptoms and ASD in middle childhood. These symptoms and disorders were associated with neurocognitive outcomes, suggesting that ASD may result from abnormal brain development in this population.

  2. About time. Since I'm certain my youngest son's severity is directly linked to those 5 days we spent in antenatal. He should have been born the moment we arrived and his heart rate dived the first time. Not 5 days later, after he'd stopped moving for 24hrs+... took them the first 24 to do the non-stress test... and after his heart rate dove during the induction.

  3. Not sure why this study isnt getting more press. Great information...