July 11, 2011 The first scientific review of all research on birth-related risk factors for autism has clarified the conditions that may contribute to the development of this neurobiological disorder. The report appears in today’s issue of the journalPediatrics. Hannah Gardener and her colleagues at Harvard School of Public Health and Brown University reviewed the scientific literature for clinical studies on birth and newborn conditions that have been associated with autism. They identified 40 individual—and sometimes conflicting—studies suitable for “meta-analysis.” A powerful statistical technique, meta-analysis allows researchers to combine and compare findings across many scientific reports to clarify and strengthen their conclusions. In doing so, Gardener and her colleagues explored 60 different birth-related conditions suspected as increasing autism risk. These included complications such as prematurity, low birth weight, multiple birth, and birth injury, as well as broader factors such as season of birth. Specifically, the researchers identified the following complications and conditions as having the strongest association with increased risk that a child will develop autism:* abnormal birth presentations (e.g. breech),* umbilical-cord complications (e.g. cord wrapped around neck),* fetal distress,* birth injury or trauma,* multiple birth (twins, triplets, etc.),* maternal bleeding,* summer birth (possibly associated with pregnancy during winter flu season),* low birth weight or small for gestational age,* physical birth defects,* low 5-minute Apgar score (a rating of overall newborn health),* myconium aspiration,* feeding difficulties,* newborn anemia or hyperbilirubinemia.
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