What pregnancy does to your body's muscles, joints and posture
Nicola Tik
Pregnancy brings a remarkable set of changes to your muscles, joints and the way your body holds itself, and understanding what is happening can make a real difference to how you move and feel day to day.
From early pregnancy, your body begins producing a hormone called relaxin. Its job is to gradually loosen the ligaments and connective tissue around your pelvis, preparing your body for birth. This is a normal and necessary process, but it does mean that joints which usually have a certain amount of natural stability start to feel a little less predictable. You might notice this in your hips, lower back, or pelvis, particularly when moving from sitting to standing, climbing stairs, or turning over in bed.
Relaxin does not only affect the pelvis. It works throughout the body, which is why some people notice increased flexibility or a sense of looseness in other areas too, including the knees and ankles.
As your bump grows, your centre of gravity moves forward. Your body responds by gradually adjusting the way you stand and move, often increasing the curve in your lower back and shifting weight through your hips and legs differently than before. These are natural adaptations, but they do place new demands on the muscles of your back, hips, and core.
Your abdominal muscles, which usually play a big role in supporting your spine, stretch and lengthen across pregnancy to accommodate your growing baby. This changes how load is shared across your trunk, and many people find their lower back and glutes work harder as a result.
Your deep core muscles, including your pelvic floor, are closely connected to how your spine and pelvis are supported. Across pregnancy, both the demands on these muscles and their ability to generate the same kind of support can change. This is not a problem to fix, but it is worth being aware of, because gentle, consistent movement tends to help the body manage these shifts better than rest alone.
Postural changes do not stop at the lower back. As your bump grows and your centre of gravity shifts, many people notice changes in the upper back and shoulders too. Breasts becoming heavier earlier in pregnancy can increase the load through the upper spine, and it is common for the shoulders to round forward a little more over time. This can contribute to tension across the neck, upper back, and between the shoulder blades.
Early pregnancy is often when hormonal changes are most noticeable, even before the bump is visible. The middle months tend to bring postural shifts into sharper focus as your body visibly changes shape. Later pregnancy places the greatest mechanical load on the lower back, hips, and pelvic floor, and this is often when discomfort becomes most noticeable day to day.
Throughout all of this, gentle movement remains one of the most useful things you can do. Keeping your body moving, in whatever way feels comfortable, helps maintain muscle support, manage load through your joints, and support your overall sense of wellbeing.