Many birthing complications appear to be risk factors for the later development of autism. An epidemiological study from Harvard University reviewing 40 studies from the literature pooled together what were the significant risk factors (Gardener et al., 2011):
* 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),
* meconium aspiration,
* feeding difficulties,
* newborn anemia or hyperbilirubinemia.
Factors not associated with being an autism risk included anesthesia, assisted vaginal delivery, postterm birth, high birth weight, and head circumference.
Many of these complications may happen together and may prove to be additive, especially when both antepartum and intrapartum conditions are present (Getahun et al., 2017). In some cases the complications may be the result of medical intervention, e.g., when labor doesn’t start on its own, a physician or midwife may use techniques to induce contractions and accelerate labor while trying to achieve vaginal birth. The drug Pitocin (a synthetic version of oxytocin) has been used for this purpose. A recent survey study concluded that there was, “…a synergistic effect between administration of labor and delivery drugs and experiencing a birth complication, in which both obstetrics factors occurring together increased the likelihood of the fetus developing ASD later in life (p=0.003)” (Smallwood et al., 2016). Other studies have only found a modest gender biased correlation (primarily affecting males) (Weisman et al., 2015). Taking into account the benefits of induced labor, caution is warranted when interpreting the findings.
The large number of assembled complications offer a confound to those individuals that propose genes as the primary determinant of autism risk. It also calls into question Neurodiversity proponents who claim that autism is a normal variation of the human genome. The aforementioned complications have in-common lack of oxygen supply to the brain. Not getting enough oxygen to the brain is extremely dangerous to infants as well as full grown adults. Without oxygen, cells die and the brain gets damaged resulting in cerebral palsy, developmental disorders and neurological disabilities. Indeed, individuals with an autism spectrum disorder who had a poor intrauterine environment may concomitantly manifest intellectual disability, often severe (Langridge et al., 2013).
A technical weakness of the above-mentioned surveys is the difficulty involved in elucidating whether birth complications cause autism or whether autism itself leads to birth complications. In addition, many of the surveys relied on self-reports which opens the door to misclassification of medical conditions by patients (e.g., what constitutes preeclampsia). By contrast, a positive of the above-mentioned studies is their clinical relevance. The presence of complications during labor and delivery may help identify children at risk for ASD and calls for early screening and intervention, when needed, to enhance their development. The results also provide evidence pointing towards pregnancy and the prenatal period as critical to those changes that propitiate autism. In this regard, they firmly entrench autism as a neurodevelopmental disorder.
Gardener J, Spiegelman D, Buka SL. Perinatal and neonatal risk factors for autism: a comprehensive meta-analysis. Pediatrics 128(2):344-55, 2011.
Getahun D, Fassett MJ, Peltier MR, et al. Association of perinatal risk factors with autism spectrum disorders. Am J Perinatol 34(3):295-304, 2017.
Langridge AT, Glasson EJ, Nassar N, et al. Maternal conditions and perinatal characteristics associated with autism spectrum disorder and intellectual disability. PLoS 8(1): e50963, 2013.
Smallwood M, Sareen A, Baker E, et al. Increaed risk of autism development in children whose mothers experienced birth complications or received labor and delivery drugs. ASN Neuro 8(4):1759001416659742, 2016
Weisman O, Agerbo E, Carter CS, et al. Oxytocin-augmented labor and risk for autism in males. Behav Brain Res 284:207-12, 2015.