Understanding the Physiology of Labour: What to Expect
newborn baby
Labour is often described as a series of stages—but to truly understand it, we need to go deeper than timeframes and centimetres. Physiological birth is an intricate hormonal, physical, and emotional journey. For parents preparing for birth in Tunbridge Wells, throughout South East England, or via online antenatal classes, understanding the clinical stages alongside the biomechanics and hormonal flow offers a richer, more empowering perspective.
🌱 Stage One: The Beginning of Labour
(Room One: The Separation Phase)
Clinically, the first stage of labour begins with regular contractions and ends with full cervical dilation (10 cm). But there’s more happening than meets the eye.
This phase can be divided into:
Latent Phase: The cervix softens and starts to dilate. Hormones like oestrogen, oxytocin, and relaxin begin preparing the uterus.
Active Phase: Contractions intensify and coordinate, thanks to a rise in oxytocin receptors in the uterus.
Physiologically, this is “Room One” — a mental and emotional shift. The birthing person starts to disconnect from external stimuli and prepare for deep internal work. Privacy, safety, and warmth help support oxytocin flow.
🧠 Hormonal activity: Oxytocin rises. Adrenaline begins to drop. The cervix doesn’t just open—it’s drawn up and over the baby’s head, like a polo-neck jumper.
🔁 Stage Two: Birth of the Baby
(Room Two: The Liminal Phase)
Clinically, the second stage refers to the time from full dilation to the birth of the baby. It is often marked by the mother’s urge to push and active participation in birthing the baby.
In physiological terms, this is “Room Two” — a liminal, altered state. The neo-cortex quiets and the limbic brain takes over, guiding primal, instinctive behaviours.
🔥 Key signs:
The birthing person may stop communicating, feel fully focused, vocalise differently, and change positions frequently.
Oxytocin and beta-endorphins surge, producing calm, pain relief, and deep focus.
The uterus acts like a piston, building up strength at the top (fundus) to push the baby downward.
🦴 Pelvic movement and fetal rotation are essential. The baby is not passive—they wriggle, rotate, and reposition to navigate the pelvis.
🌸 Stage Three: Birth of the Placenta
(Integration & the Emergence Phase)
The third clinical stage begins after the baby is born and ends with the delivery of the placenta.
This stage is often overlooked but is deeply significant. It’s the final phase of the birth journey, where the mother and baby remain physiologically linked.
🩸 Physiology at play:
The baby instinctively crawls to the breast, stimulating oxytocin and prolactin.
Oxytocin contracts the uterus, helping the placenta detach and minimise bleeding.
The baby receives the last of their blood from the placenta—a vital transfusion of nutrients and oxygen.
🧍♀️ Biomechanics: Movement and Space in Birth
Labour isn’t just hormonal—it’s profoundly biomechanical. The way the baby moves through the pelvis—and the way the birthing person moves their body—can significantly impact birth progression.
Key concepts include:
Pelvic mobility: The pelvis is not a fixed structure. Movement like walking, leaning forward, or hip-circling can optimise space for baby’s descent.
Fetal positioning: Babies typically rotate to align their widest part (e.g., the head) with the widest part of the pelvis. Encouraging positions that support optimal fetal positioning (OFP) can help.
The role of gravity: Upright, forward, and open (UFO) positions use gravity to aid descent and alignment.
Educating parents about how to move in labour, when and why to adjust positions, and how birth partners can offer physical support can promote smoother birth.
🌍 In Summary
Labour is not a linear race to 10 cm—it is a coordinated hormonal and biomechanical process, supported by movement, environment, and instinct. Whether you're attending antenatal sessions in Tunbridge Wells, across South East England, or online, understanding this physiology of birth is truly important.
