Levels of placental hormone allopregnanolone (ALLO) were found to rise during pregnancy and peak as fetuses approach full term, revealed multi-institutional research presented during the Pediatric Academic Societies (PAS) 2018 annual meeting.
The placenta is the source of more than 200 different hormones that each uniquely contribute to the smooth running of the pregnancy and the fetus' overall health. Researchers know ALLO is made in the adult brain in response to stress and modulates neuronal excitability. Less is known about how placental ALLO levels evolve during pregnancy and in newborns shortly after birth.
Anna Penn, M.D., Ph.D., a neonatologist/neuroscientist at Children's National Health System, and colleagues created a designer experimental model to study how premature loss of ALLO alters orderly brain development. Knowing more about the interplay between ALLO and normal development of the cortex, the outer layer of the cerebrum, is a first step that could lead to strategies to rescue this vital brain region. "The cortex is basically the brain's command-and-control center for higher functions. In our experimental model, it develops from the middle of gestation through to the end of gestation. If ALLO levels are disrupted just as these cells are being born, neurons migrating to the cortex are altered and the developing neural network is compromised," says Dr. Penn, senior author of the research presented at PAS 2018. "We're concerned this same phenomenon occurs in human infants whose preterm birth disrupts their supply of this essential hormone."
"Pregnancies complicated by hypertension tended to correlate with lower ALLO levels, though this finding did not reach statistical significance. This suggests that ongoing placental dysfunction and ALLO loss, not the increase that we expected to be caused by stress, may alter cortical development in these pregnancies and put babies at risk," Dr. Penn adds. "In addition, having the largest neonatal sample set to date in which multiple steroid hormones have been measured can provide insight into the shifting hormone patterns that occur around 36 weeks gestation, just prior to term. Hopefully, restoring the normal hormonal milieu for preemies or other at-risk newborns will improve neurological outcomes in the future."