Biomechanics Of Labour

Introduction

When talking about biomechanics in general, we can define it as the study of mechanical principles applied to any biological system. 

Here we are focussing on the biomechanics of labour. In simple terms, it would mean the analysis of forces, movements, and interactions within the mother’s body during the different stages of labour. Biomechanics and positional changes can help babies to rotate and turn to navigate the pelvis.¹

"Vaginal birth is a remarkable event about which little is known from a biomechanical perspective”

Ashton-Miller and DeLancey 2010

Why is this study important?

We are living in an era where the two worlds - ‘medicalised’ and ‘natural’ exist. It is essential to understand the natural mechanics of birth which would help ease the process naturally first followed by medical interventions when required. 

Understanding the biomechanics of labour is important for healthcare professionals to optimise obstetric care, prevent complications, enhance overall maternal and fetal well-being during delivery, and be a part of the holistic management of the situation. 

Overview of labour

Labour is divided into three stages:²

The first stage - early labour: It initiates with the cervix dilation and is often accompanied by irregular contractions. The active labour within the first stage, involves more intense and regular contractions, driving further cervix dilation til it reaches the maximum (10cm)

The second stage - marks the delivery of the baby. It is also called the pushing stage. 

The third stage is the delivery of the placenta. 

In recent years, we have come to recognise a fourth stage which encompasses the initial recovery period after childbirth. 

Throughout these stages, various muscles and joints collaborate in a synchronised manner, such that the joints become looser and certain muscles relax to make way for the baby. Once we understand how the baby moves within the pelvis, we can effectively implement certain maternal movements which would ease the baby’s journey for both the mother and the baby. 

A simplified approach

Without going into the boring details of the anatomy and biomechanical terms involved, let me take you on the journey of childbirth as viewed through the lens of ‘natural birth’. But what is a ‘natural birth’ you would ask?

These evidence-based recommendations are:³

• Birth should start on its own
• There should be freedom of movement during birth, and other positions besides lying on the back should be supported
• Emotional and physical support should be given to the pregnant woman throughout the birth
• Any unnecessary intervention should be avoided
• Natural and active pushing techniques should be preferred at birth
• After birth, the mother and baby should stay together

How to implement biomechanics at birth

Let’s understand the pelvis first. The pelvis has three main areas within it, and the inlet is the top part of the pelvis, where the baby enters. And there is the mid pelvis, which is midway within the pelvis. And then, there is the outlet, which is at the bottom of the pelvis where the baby comes out.⁴

Depending on how a baby is positioned where a baby is within those three areas of the pelvis, we have the chance to use specific positions to create more space to help facilitate the baby’s rotation which would help in baby’s passage through the pelvis. 

A few simple movements

This topic requires a course to completely understand the impact of every movement, but I have compiled a few basic, easy to implement movements which may help you during labour. 

Any movement is good

Before we dive into different positions, remember the golden rule - move! We are instinctually inclined to birth, so, if you cannot follow any particular exercise or position, listen to your instincts.

Sifting

This movement can be used during pregnancy and early labour. It involves the mother on her knees with arms resting on a chair or bed. Her pregnant belly is supported by a long shawl and her partner gently rocks or sifts her abdomen. This will help release any tension within the ligaments and even provide relief when done between contractions. 

Abdominal lift and tuck

This technique is done with the help of your partner, doula or midwife. The woman slightly tilts her pelvis in the front, flattening her lower back, her partner lifts the abdomen a couple of cm and holds the position during the contraction for a few contractions consequently. This position should be avoided if the baby’s head is not in the right direction or the water is broken.⁵ 

Deep supported squats (knees apart, feet in)

With the help of a partner, wall or a birth ball, the mother may stay in a deep squat with knees apart. This helps in the opening of the pelvic inlet and helps the baby enter the pelvis. Similarly, other positions to help open the inlet include: Sitting with knees wide apart and back straight (perhaps on the wall or bed); Standing, walking or slow dancing with arms above shoulders (imagine hanging on your partner) to help lift ribs up and off of the abdomen; and rocking front to back on a birth ball or on all fours.⁶

Side-lying release

This is like a static stretch and helps women who are experiencing prolonged labour.⁷ It can also be done during pregnancy. It involves the mother lying on her side at the edge of the bed, with her top leg hanging over the bed. She may stay in this position for 15-30 minutes or longer during pregnancy. This position will help open the mid-pelvis.

Asymmetric movements

Any movement that involves one side of the body more than the other will help the movement of the baby down. Imagine trying to fit a softball through a bottleneck - you would twist and turn, trying to squeeze one side more than the other. In a similar method, asymmetric movements of the pelvis would help the baby’s head navigate through the pelvis. A few such movements include lunges (sideways), climbing stairs, and rocking sideways or in circles on a birth ball. 

Knees together, feet apart (all fours)

Once the baby has moved within the mid-pelvis, it’s time to open the pelvic outlet. One position that would help is with the mother on all fours, with her knees close together and feet far apart (opposite to what was done during the inlet opening). Other similar positions would include side lying with knees together and feet apart (using a pillow or peanut ball), a semi-squat while holding onto something above your belly (as if hanging) with toes turned in. 

Rest

I almost completely forgot. Resting during labour is extremely important. It would be beneficial if we choose a position of resting that would even help with labour. One such position is the exaggerated lateral position. This requires the mother to be lying on her side, slightly rolled forward with pillows under her belly. The top leg is bent at the knee and forward with pillows under. This position might help the mother relax as well as help the baby get into the optimum position. 

What about the ‘pushing stage’?

During this stage, usually, any upright position with some support is helpful. Supported squatting may be a good idea. This position has proven to shorten the stage.⁸ Some women prefer to push in a semi-sitting position or even side lying. 

An important note to remember during the pushing stage would be to avoid pushing or labouring while on your back and follow the natural spontaneous urge to push versus guided or directed pushing.⁹

Summary

In this article discussing the journey of a baby during labour, we looked into the application of mechanical principles to a mother's body during childbirth. While focusing on the natural mechanics of birth, the article emphasises the importance of understanding biomechanics to facilitate a smoother process. The article simplifies the biomechanical aspect of childbirth, presenting evidence-based recommendations for a 'natural birth.' We also introduced various movements and positions that can be implemented during labour to optimise the mother's and baby's well-being. I hope the reader is guided through the easy-to-understand techniques, emphasising the significance of movement, rest, and instinctual responses during this amazing journey.

If there is one thing you would like to remember from this article - remember to follow your instincts, take an upright position and don't forget to rest!