Premature Birth and Low Birth Weight Have Previously Been Linked to ASD; Now, Post-Term Birth Also Shows Vulnerability
Post-term births from pregnancies lasting more than 42 weeks account for 5-10% of deliveries in developed countries. A new meta-analysis from Iranian researchers shows that post-term birth can be considered a risk factor for autism spectrum disorder (ASD). The authors indicate that the reasons behind this association are not yet fully understood. However, they suggest that prolonged labor, cephalopelvic disproportion, and shoulder dystocia, conditions that can accompany post-term birth and are also linked to oxygen deficiency, could lead to abnormal neurobehavioral problems. Additionally, the researchers propose that uteroplacental insufficiency, a non-optimal ‘old’ placenta that offers fewer nutrients and less oxygen than a term fetus requires, may be related to the post-term birth association. The lack of nutrients and oxygen experienced in this condition may predispose the infant to abnormal fetal development, leading to atypical neurobehavioral development. Finally, the authors indicate that it is possible that a disturbance of the placental clock, which regulates pregnancy duration, is involved. A marker of this clock is the placental secretion of corticotrophin-releasing hormone, which is lower in post-term deliveries than in term deliveries. The corticotrophin-releasing hormone is a sign of this clock and a principal regulator of the maternal–fetal hypothalamic–pituitary–adrenal (HPA) axis. Earlier research has suggested that placental endocrine dysfunction or maternal stress at critical times during fetal development may influence the fetal HPA axis, leading to neuroendocrine abnormalities that could increase the child’s susceptibility to neurobehavioral disorders later in life.
