The Biology of Stress: Understanding Your Nervous System for Birth and Beyond
Stress is not just a mental state—it’s a full-body experience. Our nervous system is constantly reacting to our external environment, shaping how we feel, act, and even how we give birth. Understanding the biology of stress and the role of the autonomic nervous system can empower you to navigate the intensity of birth with more ease. One of the most useful models I use in my work is the Polyvagal Theory, developed by Dr. Stephen Porges. Also sometimes referred to as the Science of Safety, this theory explains how our body shifts between different states of safety and survival.
The Three Nervous System States
According to the Polyvagal Theory, our autonomic nervous system has three key states:
Safety & Connection (Ventral Vagal State)
In this state, we feel calm, connected, and safe. Our heart rate is regulated, digestion functions well, and we can engage with others. In birth, this state allows oxytocin to flow, muscles to relax and helping labor progress smoothly.
Fight or Flight (Sympathetic State)
When we perceive a threat (the emphasis here is on perceived, because most likely you’re not being attacked by a tiger), our nervous system activates the sympathetic response—our body mobilizes energy to fight or flee. Heart rate increases, muscles tense, and stress hormones like cortisol and adrenaline go up. In birth, this state can slow labor, making contractions more painful and less efficient.
Freeze & Shutdown (Dorsal Vagal State)
When stress becomes too overwhelming and we feel that we cannot escape (meaning fight or flight is not an option anymore), the body shifts into dorsal vagal activation, a state of freeze, like you’re feeling paralyzed or stuck. This can show up like low in energy, constant fatigue or dissociation. In birth, this might manifest as feeling stuck or powerless.
The Personal Nervous System Map: Triggers & Glimmers
Triggers are signals that push us into fight, flight, or freeze. These could be certain words, smells, or even medical settings that remind us of past stress. The trigger subconsciously brings our nervous system back to that stressful situation
Glimmers are small cues of safety and connection that help us back to regulation. This could be a warm touch, a familiar song, the caring presence of a loved one or a certain smell that reminds you of a pleasant situation (fun fact: Smell circumvents the neocortex, the thinking brain, and reaches the nervous system like a fast lane)
By identifying your personal glimmers, you and your birth team can create a supportive environment that helps you stay more regulated during labor. For example, if soft lighting, specific essential oils and/or a foot massage makes you feel calm, incorporating those elements into your birth space can make a big difference.
Using This Knowledge in Birth
Taking the time now to explore your nervous system and discover what supports you can be a powerful gift to your future self during labor. The more you familiarize yourself with your triggers and glimmers, the easier it will be to shift into a state of safety when it matters most.
Prepare your birth space
Surround yourself with elements (and people) that bring you safety and connection.
Communicate your needs
Let your birth team know your glimmers and preferred forms of support, for example massage, positive affirmations, or simply guarding your space so you can turn inward and feel safe.
Practice regulation techniques
Gentle movement, stretches, and massage can help shift your nervous system back to a state of safety.
Birth is an intense experience, but when you understand your nervous system, you’ll gain tools to navigate it with more trust and confidence. By mapping your triggers and glimmers, you create a personalized guide for yourself and your support team—helping you stay connected to your body and your inner strength.
A short and insightful quiz to help you feel more confident and prepared.
Empowering Mothers, Not Just Births
Birth is not only about making babies. Birth is about making mothers – strong, competent, capable
mothers who trust themselves and know their inner strength.
-Barbara Katz Rothman-