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Exercise and how your body changes in pregnancy

Pregnant women in exercise classYour body will undergo a number of anatomical and physiological changes in pregnancy. So how do those changes affect the way you exercise while you are pregnant?

Unless you have complications, you should continue to exercise while pregnant. The general rule is that you can continue with whatever exercise you did before you fell pregnant—although you should avoid sports where there is a risk of falling or being hit in the abdomen (horse riding, martial arts etc). You should always chat to your health care provider after your individual situation before beginning an exercise routine.

Here are some of the ways your body will change during your pregnancy, and how that relates to your exercise.

Exercise and how your body changes in pregnancy

Increase in body weight

For someone in a healthy weight range, the average weight increase during pregnancy is 10-15kg, although everyone is different. Half of this is the uterus, baby, and amniotic fluid, and the other half is body fat stores, fluid, and breast fluid.

This increase in body weight will increase the level of jarring force and stress on your joints by up to 5 times in activities such as running and jumping.

Change in body shape

The change in your body shape moves your body’s centre of gravity forwards and increases the inward curve of your lower back. This change alters balance and coordination and may make activities/sports that require high levels of balance and co-ordination unadvisable (e.g. rollerblading) as you are more likely to fall.

As your baby grows, your uterus will push up onto your diaphragm. This can make you feel more short of breath than usual when you exercise, and sometimes short of breath when you’re just resting.

The increase in size and weight of your breasts can also cause rounding of the shoulders and increases the outward curve of your upper back. It is important to be aware of this and try to take extra care with your working and resting positions.

Hormonal changes and looser ligaments

During pregnancy, your body releases hormones that support pregnancy and are designed to gradually loosen your pelvic joints to prepare for childbirth.

However, all areas in the body become affected by these hormones and become gradually looser. This may pre-dispose pregnant women to joint injury and most likely contributes to low back pain and pelvic pain during pregnancy. Many women feel like their pelvis is ‘loose’.

You should take care with activities that involve high impacts such as jumping or running, or activities that involve quick changes of direction, jerky or ballistic movements (like boxing), or excessive stretching. Core abdominal and pelvic floor exercises will be important to help strengthen and support the area.

Even the walls of your veins are softened by pregnancy hormones and this can contribute to varicose veins.

Increase in blood volume and fluid retention

Blood volume increases by up to 40-50% during pregnancy. Together with the effect of hormones on your blood vessels, this increased blood volume can lead to decreased rate of blood flow back to the heart, ankle swelling, and pooling of blood in your legs.

Sodium retention in your kidneys may also contribute to swelling of your hands and feet.

In addition, minerals (like calcium and magnesium) from your diet are redirected to growing a healthy baby. This can affect your muscle and nerve function and lead to leg cramps.

Increase in resting heart rate and respiratory rate

Resting heart rate increases by 7 beats per minute (bpm) in the first four weeks of pregnancy and 15-20 bpm in mid-pregnancy.

Your body is already in what could be termed ‘an exercise state’ during pregnancy – your body is working harder. This is why it isn’t recommended to use target heart rate to determine the intensity of exercise. Instead the intensity should be measured using the expectant mothers’ rating of perceived exertion. A ‘moderate’ rate of exertion is considered safe during pregnancy.

Abdominal muscle changes

As the size and weight of your uterus increases, your abdominal muscles will lengthen and the stretch the connective tissues that run between them. This connective tissue is called the linea alba and some stretching here is a normal part of pregnancy. And excessive amount of stretching is called a diastasis recti or rectus diastasis.

Pregnant women should avoid exercises and activities that lead to increased strain through the linea alba like sit-ups where a central bulge is visible as this can increase the risk of a large diastasis recti. Most diastasis recti recover well after the birth.

Pelvic floor

The increased weight of your uterus on your pelvic floor combined with the effect of hormones can cause your pelvic floor muscles to stretch and weaken. High-impact exercises or activities (like lifting heavy loads) will also increase the stress on your pelvic floor while it is in a stretched and weakened state and should therefore be avoided. Childbirth itself (vaginal delivery) can also cause damage to the pelvic floor muscles.

It is important to begin conditioning your pelvic floor muscles from the start of pregnancy to prevent complications such as increased perineal tearing, incontinence or bladder leakage. Pelvic floor exercises should continue throughout the pregnancy and recommence as soon you feel it is comfortable after birth.

When working your pelvic floor, you should focus should on activating the muscles you would use to hold onto wind or stop a wee. Start by practising turning these muscles on and off. Once you have mastered that, use them when you need extra support from strain like when you cough/sneeze, are busting for the toilet or go to lift your toddler. To strength your pelvic floor aim to increase the holding time for about 10 seconds and repeated up to 10 times. Start with  Start with 5 repetitions if 10 is too much and build up to 10 per session. You should do this at least 3 times per day.

Pelvic floor exercises can be practiced in a variety of positions such as side lying, standing, or sitting.

Other hints for pelvic floor health are to drink plenty of water during pregnancy (1.5-2 litres per day), avoid constipation, and not push and strain when urinating and defecating (try consciously relaxing and releasing your pelvic floor).

Decrease in blood pressure

Blood pressure falls during the second trimester due to the development of blood vessels to supply the growing placenta. After about the fourth month, rapid changes of position (e.g. from lying to standing) may cause dizzy spells and should be avoided.

Lying on your back (e.g. doing leg exercises on your back in exercise classes) should also be avoided after the fourth month as the weight of the baby on major blood vessels in the abdomen can slow down the return of blood to the heart. Going to sleep on your back is associated with an increased risk of stillbirth in late pregnancy.

Stop exercise immediately and seek medical advice if any of the following is experienced during or after exercise:

  • Dizziness or faintness that does not resolve quickly
  • Headache
  • Uterine contractions
  • Vaginal bleeding
  • Amniotic fluid leakage
  • Nausea or vomiting
  • Extended shortness of breath once you finish exercising
  • Back or pelvic pain
  • Decreased foetal movements
  • Sudden swelling of ankles, hands and face

-written with information from Jenny Birckel from Preglates

The content in this article should be used as a guide only. If you experience any health-related concerns you should contact your local healthcare provider or nearest emergency department.

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1 Comment so far -
  • Mel Dawson says:

    I just wanted to share how much yoga during pregnancy changed my mental outlook and my birth experience. With my little girl Heidi I walked and swam and that was useful but I often felt breathless and uncomfortable. Pre Natal yoga with my second Tom taught me valuable breathing skills, allowed my very narrow hips and pelvis some time to expand and assisted in connected with my body again – instead of feeling out of control I felt empowered and more connected with my baby. I gained less weight and had a much better labour! I’d love to take this opportunity to thank yoga and promote The Pre Natal Yoga course at Sacred Place Yoga (Blacksmiths NSW) 49 71 6901…were so lucky to have trained midwife as well as a yoga teacher on board. X

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