2026 ECNP Congress

T.04

Uncovering how maternal stress impacts the neuroimmune system in pregnancy: from brain to placenta

Anna Sancho Balsells — E.E. Hoeksema, M.H. Mulder, M. di Trapano, J. Kotah, N. Brouwer, V. Zonca, V. Begni, A.M. Cattaneo, M.A. Riva, B.J. Eggen, A. Korosi · University of Amsterdam, Swammerdam Institute for Life Sciences, Amsterdam, Netherlands

2026 ECNP Congress

Introduction

Pregnancy is a dynamic physiological state that requires precise immune adaptations to support fetal development and maternal health. Stress during this period can further alter immune responses and disrupt neuroimmune balance, with lasting consequences for mother and offspring. Most work on prenatal stress has focused on offspring neurodevelopment, whereas its impact on the maternal brain, highly relevant for perinatal mood disorders such as postpartum depression, remains poorly understood.

In this talk, I will address three questions:

  1. How does pregnancy reshape the maternal brain’s neuroimmune system, focusing on microglia?
  2. How does prenatal stress modify these pregnancy‑induced microglial changes?
  3. Does the immune system, particularly in the placenta, contribute to transmitting maternal stress to the fetus?

Approach We use a prenatal stress paradigm in which dams undergo repeated immobilization stress during late gestation. Before delivery, dams are sacrificed and maternal brains, plasma, placentas, and fetal brains are collected. We combine microglial FACS sorting with transcriptomic profiling in maternal and fetal brains, immunohistochemical analysis of microglial density and morphology using Iba1 and an unbiased clustering pipeline, and immunofluorescent characterization of placental immune cell populations.

Results

Prenatal stress reduces maternal body weight and litter size and increases anxiety‑like behavior. Transcriptomic analyses reveal that pregnancy alone induces major changes in maternal microglia, and that stress further reshapes this landscape. I will conclude by outlining ongoing work on microglial morphology, fetal microglia, and placental immunity, and by discussing how these findings may inform mechanisms linking pregnancy stress to maternal mental health risk.