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Anatomy of pregnancy and birth - abdominal muscles

3-minute read

The most obvious physical sign that a woman is pregnant is the growing abdomen – or, ‘baby bump’ – which affects the abdominal muscles. Understanding how the abdominal muscles work is helpful for pregnant women. Strengthening your abdominal muscles during and after pregnancy helps these muscles work as they should.

What are abdominal muscles?

The abdominal muscles are those in the front of the torso (also referred to as the trunk), between the ribs and the pelvis. The abdominal muscles in both pregnant and non-pregnant people are designed to support the torso. This allows movement, such as walking and bending. The strength of the abdominal muscles holds the internal organs in place.

There are 4 types of abdominal muscles — the external and internal obliques, and the transversus and rectus abdominis — which come in pairs (one on either side of the torso), and work together to:

  • stabilise the torso and keep organs in place
  • support movements between the rib cage and the pelvis
  • allow the torso to twist

The term 'core muscles' is commonly used to describe the deepest abdominal muscles and the muscles in the back, which attach to the spine or pelvis. The core muscles are responsible for keeping the body stable and balanced, and to protect the spine.

What happens to abdominal muscles during pregnancy and birth?

During pregnancy, the growing baby stretches the abdominal muscles. The mother's abdomen changes shape during the pregnancy because of the growth and movement of the baby, and so her abdominal muscles are also affected. For instance, the abdominal muscles progressively stretch as the pregnancy proceeds as the womb expands.

During the birth, most of the pushing is done by the uterus, not the abdominal muscles. After the birth, the abdominal muscles will feel weak and stretched, but these muscles should eventually become toned again.

How can abdominal muscles be strengthened during pregnancy?

Abdominal muscles overstretch during the pregnancy since the baby rests forward on them, so it is important that these muscles are exercised. Strengthening the abdominals can help pregnant women stay active and use the abdominal muscles for day-to-day activities, such as support and movement. Exercising abdominal muscles during pregnancy also helps them return to their original length and shape after the baby is born.

Safety tip: Sit-ups and crunches are not recommended during pregnancy. This is because the stretched abdominal muscles in a pregnant woman do not work the same way as when she is not pregnant. These exercises are usually done while lying on your back. This position can cause dizziness in pregnant women because the weight of the baby rests on major blood vessels.

A safe way to work the abdominal muscles and improve core strength is to draw in the muscles without moving your spine – as though sucking your belly button in, towards the spine.

Pregnancy-specific exercise classes can also help build and maintain core strength, such as yoga and Pilates classes for pregnant women. They tend to focus on low impact exercises and feature movements that help with core strength, breathing and relaxation, strengthening abdominal muscles, the pelvic floor and relieving lower back pain.

What problems can happen to abdominal muscles in pregnancy?

The enlarging uterus causes the abdominal muscles to stretch. It may cause the two bands of muscles that meet in the middle of the abdomen to separate. This condition is called 'diastasis recti'. This muscle separation can sometimes appear as a bulge in the middle of the abdomen. The condition may cause pain in the lower back or it might become hard to lift things or do other physical activities. Abdominal muscle separation is usually managed after childbirth with exercise and physiotherapy. Occasionally surgery is required.

If you think you may have diastasis recti, see your doctor or maternal health service.

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Last reviewed: October 2020

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