What Is Biomechanics in Birth — And Why You Need It in Your Birth Prep

When you hear the word biomechanics, you might think of sports or engineering. But it’s also one of the most powerful and underused tools in birth preparation. Understanding how your body and your baby move together during pregnancy and labour can make a huge difference to how your birth unfolds, especially if you want to reduce the risk of intervention, support birth physiology, or help labour progress smoothly.

Let’s break it down… midwife to midwife, mother to mother.

🤰 What Is Biomechanics in Birth?

In simple terms, biomechanics is the science of how your body moves. In pregnancy and labour, it refers to how your bones, muscles, ligaments, and joints work together to:

• Make space for your baby
• Support your baby’s position
• Help your baby rotate and descend through the pelvis during labour

Your pelvis isn’t a fixed bowl. It’s a dynamic structure… it moves. And that movement, combined with your baby’s own reflexes and movements, is what makes physiological birth possible.

🔄 Why Biomechanics Matters in Your Birth Preparation

Most antenatal classes focus on what to pack in your hospital bag or how to time contractions. But very few talk about how to use your body to help your baby find their way out.

When you understand biomechanics, you can:

• Encourage your baby into an optimal position for birth
• Reduce the risk of a “stuck” baby or stalled labour
• Help labour progress more smoothly
• Support a quicker, less painful labour
• Lower your chance of interventions like assisted delivery or Caesarean

In short: knowing how to move, when to rest, and how to use gravity and alignment can help your birth go better.

🔄 The Problem with Back-to-Back (OP) Babies

You might have heard the phrase back-to-back or OP (occiput posterior). This is when baby’s spine is lined up against your spine. While it’s not dangerous, it can make labour:

• Longer
• More painful (especially in the back)
• More likely to lead to epidural, instrumental birth or Caesarean

When a baby is in an optimal position (occiput anterior or OA), they tend to tuck their chin to their chest. This means a smaller diameter of the head navigates through the pelvis. But when a baby is back-to-back, their chin is often lifted. This creates a larger head diameter entering the pelvis, which can cause more difficulty and delays during labour.

📊 Why Are More Babies Back-to-Back Now?

Here’s where modern lifestyles come in. There are a few big culprits behind the rise in OP babies:

1. Too Much Sitting

We spend hours in cars, at desks, or slouched on sofas. This encourages the pelvis to tuck under and reduces space at the front of the pelvis, encouraging baby to face the spine.

More importantly, prolonged sitting shortens key ligaments and muscles, like the psoas and iliacus. When these structures tighten, they reduce the space in the pelvis and make it harder for baby to rotate into an optimal position.

2. Less Daily Movement

Historically, pregnant women squatted, walked, lifted, stretched. They used their bodies dynamically. Modern pregnancy is often much more sedentary because of how society is compared to how it once was. This lack of variety in movement can cause muscle imbalances and asymmetry, which affect how the pelvis opens and how the baby navigates through it.

3. Reclined Resting Positions

Recliners, deep sofas and slouching in bed all encourage posterior positioning. Without realising it, we’re nudging babies into the back-to-back position every evening.

🤔 A Quick Note: Biomechanics Isn’t Just About “Turning the Baby”

There’s a misconception that biomechanics is all about getting into a clever position to turn your baby.

The goal of biomechanics is to create space by releasing tension, balancing the pelvis, and stretching shortened ligaments. When the pelvis is balanced and muscles are supple, babies can move more freely into the position that’s right for them, often without you needing to force anything.

So it’s not about manipulating your baby. It’s about optimising your body’s alignment so your baby can follow their natural path.

🧼 How Biomechanics Can Help You Avoid Interventions

When baby is well-aligned, head-down and with their back towards your belly (occiput anterior, or OA) labour is often shorter, easier, and more straightforward. This position encourages the baby to tuck their chin to their chest, presenting the smallest diameter of the head to the pelvis.

Back-to-back babies, on the other hand, often lift their chins, resulting in a larger head diameter navigating the pelvis. This can lead to:

• Slower, more painful labour
• Increased risk of epidurals
• Higher chance of instrumental or Caesarean birth

A good understanding of biomechanics in labour can help you:

• Open your pelvis where and when it matters
• Encourage rotation of a back-to-back baby
• Keep labour progressing if things slow down
• Avoid a cascade of interventions

🧘‍♀️ What You Can Do: Birth Prep with Biomechanics in Mind

You don’t need to be a yoga queen or Pilates devotee to make a difference. Small, simple changes have a big impact.

Daily Tips:

• Sit forward on a birth ball or upright chair, especially in late pregnancy
• Use stairs and walk daily, even for 10 minutes
• Avoid reclining on deep sofas — sit on the edge or use cushions for support
• Balance rest and movement — side-lying is better than flat on your back

In Labour:

• Use upright, forward and open positions
• Try asymmetrical movement like lunges or one-legged kneeling
• Keep your pelvis mobile and aligned
• Use rebozo techniques, stairs, or side-lying release if needed

💡 If you want to do more specific and intentional biomechanics movements. On The Birth Chapter, you’ll find specific daily and weekly biomechanics-based positions you can follow to help optimise your pelvis and support your baby into the best position for birth. These movements are simple, effective, and designed to work with your everyday routine.

📃 The Evidence of Biomechanics in Birth

Biomechanics in birth isn’t just anecdotal, there’s growing evidence that movement, positioning, and pelvic balance can significantly improve outcomes for both mothers and babies.

A retrospective study published in the British Journal of Midwifery evaluated the effects of incorporating a biomechanics toolkit alongside the Labour Hopscotch Framework. The results were impressive:

• Spontaneous onset of labour increased from 57.2% to 72.2%
• Births before 41 weeks rose from 33.2% to 91.8%
• Induction rates decreased from 42.8% to 27.8%
• Emergency caesarean section rates following induction dropped from 33.1% to 23.8%

These findings suggest that using biomechanics proactively in pregnancy and labour doesn’t just feel better, it works. When the pelvis is balanced and the baby is in an optimal position, the body is more likely to go into labour spontaneously, progress more smoothly, and avoid interventions.

🧠 Ready to Learn More?

In my hypnobirthing online course, there’s a comprehensive section dedicated entirely to biomechanics, giving you the knowledge and confidence to use your body wisely in both pregnancy and labour.

You’ll learn:

• How to prepare your body for an optimally positioned baby
• What movements and positions support pelvic balance
• How to respond if baby is back-to-back or if labour slows down
• Which positions to use at each stage of labour depending on what’s happening

There’s also a downloadable cheatsheet to help you quickly choose the right position when you need it… ideal for partners and birth workers to follow too.

Because knowledge is power and movement is medicine.