We are often asked “what is safe exercise in pregnancy?” There is no question – research has consistently shown that keeping fit and active during pregnancy is terrific for both the mother and the unborn baby.
However, many exercises require modifications to be considered safe during pregnancy.
And what’s important to know is that there is a difference between something that is ‘unsafe’ in pregnancy (ie. potentially harmful to the unborn baby) versus something that may be in the category of ‘weigh up the pros and cons’ (ie. has the potential to increase the risk of pelvic floor issues, join pain or abdominal strain during pregnancy in some women).
You know what? Almost all types of exercise are actually safe in pregnancy. For uncomplicated pregnancies, for the most part we don’t need to wrap ourselves in cotton wool, and keeping up regular exercise has been shown to have HUGE benefits for both mother and baby.
If we take scuba diving and other ‘pressure’ related exercise out of the equation, there are actually only 4 main types of exercise that fall into the category of ‘unsafe’ in pregnancy. And some of these are a bit controversial…
In the blog that follows, we are going to explain to you what the four potentially ‘unsafe’ types of exercises are during pregnancy, are and the changes that you can make to keep exercising safely.
Change #1: Avoid exercise with a risk of falling or a force to the tummy
In the early weeks of pregnancy, the little growing baby is protected by the bony brim of the pelvis.
When it grows bigger however, and comes above the pelvis, there is no bony protection anymore. Don’t get me wrong – the baby is still heavily cushioned by the amniotic fluid and is very well protected from little bumps and knocks.
But we have to be careful when it comes to bigger forces, and sometimes these could occur during exercise. It is recommended that these things should be stopped after approximately the first trimester (when you start to ‘show’ is sometimes used as the indication that the uterus is expanding beyond the pelvic brim).
Some examples of exercise that may cause a fall, a knock or a force to the pregnant abdomen:
Basketball, netball, hockey
Gymnastics, surfing, horse riding
Gym exercises involving lifting heavy weights in a way that could fall onto the stomach
Gym exercises involving a possible fall onto the abdomen like box jumps
Change #2: Adjust your intensity so that you can still hold a conversation
When you’re pregnant, your heart has to pump blood and oxygen around two cardiovascular systems instead of one.
Our bodies are extremely clever and compensate for this by increasing blood volume, increasing the rate at which our heart beats, and increasing the amount of blood pumped out with each heart beat. But inevitably, what this means is that even from very early in pregnancy, you have more load on your heart and lungs than usual.
This may mean that you feel short of breath with much lower levels of exercise than usual – walking up stairs might suddenly feel like a bigger effort than it used to, even before you’ve told people that you’re pregnant!
Because of this, exercising at high intensities can lead to decreased blood flow and oxygen to the baby.
The recommendation here, in a nutshell, is:
Keep regularly exercising in a way that gets your heart rate up – at least 150 minutes a week of cardio exercise is highly recommended
Keep this exercise at a level where you could talk, but not sing – work hard enough to get a little puffed, but not so hard that you couldn’t concurrently chat to the person next to you. This is called ‘The Talk Test’.
Monitoring exertion in this way has been shown to be a more accurate representation of what’s happening with the baby than monitoring heart rate.
If you’re an elite athlete, or used to exercising regularly at high intensities, it has been shown that this can be safe to keep doing in pregnancy as long as you’re well monitored.
Change #3: Avoid exercises that involve lying flat on your back
This recommendation only applies to women who are further along in pregnancy. And to be honest, it’s a bit of a controversial one…
Let me explain.
When your uterus starts to take up more space in your abdomen, it means that the other abdominal contents need to shift to make space. This can cause pressure on different organs, which in turn can cause different symptoms – like constipation or reflux.
Other things that get more pressure on them are the important blood vessels that bring blood back up to the heart. When your uterus gets heavier, and you lie flat on your back, more pressure than usual is put onto these blood vessels. For this reason, it is advised not to spend an extended amount of time lying flat in your back in the second half of pregnancy.
There are quite a few types of exercise that involve lying flat on your back, and could cause a decrease in blood flow to the baby – for example, abs exercises like ‘bicycle’, arms exercises like ‘bench press’ and leg exercises like ‘bridging’.
In some women, these exercises can cause them to feel symptoms such as dizziness, lightheadedness or a general ‘icky’ feeling.
In other women, they can do these exercises, or rest lying on their back, with no symptoms at all, even late in pregnancy.
The controversy is about whether it should only be women who are symptomatic who avoid exercising on their back, and how many weeks pregnant does this start to be an issue (some guidelines say 16 weeks, some say 28 weeks, some don’t say a number of weeks at all).
In a nutshell, here is our opinion based on the research…
Although overall, the research is unclear about whether or not to avoid exercise lying on your back, there are some individual studies that showed abnormal heart rate and blood flow to the unborn baby when women exercised on their back versus in left sidelying.
There are so many ways you can exercise that DON’T involve lying on your back – you can swap these things out so easily for exercises in 4 point kneeling, modified side plank, modified bridging with shoulders on a ball etc.
Therefore we advise women in FitRight classes to swap out supine exercise for other options after approximately 18-20 weeks (when the uterus is getting bigger) or earlier if they feel dizzy or light headed in this position.
Change #4: Avoid overheating
During pregnancy, it is advised to avoid overheating for the health of the baby, especially in the first trimester, and this is often discussed in relation to exercise.
Core temperature increases of more than 1.5 degrees in the mother have been shown to have the potential to cause neural tube defects in early pregnancy, and therefore it is recommended to consider the following:
Always exercise in spaces that are well ventilated
Avoid exercise in pools hotter than 33 degrees
Avoid bikram yoga or other exercise where the room is deliberately heated
This guideline is also a slightly controversial one however… because research has not shown that exercise, even at a very high intensity, can raise core temperature by 1.5 degrees. The only thing that is likely to do that is being immersed in very hot scenarios for long periods of time like a sauna.
Personally, we would still recommend avoiding Bikram yoga and high intensity exercise in a confined space after you find out you’re pregnant. But we wouldn’t be too concerned about getting a bit hot a sweaty in a park workout or a PT session during pregnancy – as long as it’s moderate intensity exercise it’s very unlikely to be raising your core temperature to dangerous levels.
So there you go – the four main changes that international guidelines recommend that pregnant women make in order to keep your exercise regime safe for your unborn baby.
No mention of avoiding twisting, avoiding overhead arm exercises, avoiding deep squats, or other pieces of advise that you may have heard, but that have no scientific evidence behind them.
Also no mention of things like high impact exercise, weight training or abdominal muscle exercises – because although these things may not be the best for the mother’s pelvic floor, joints, and abdominal muscles, it is important to differentiate that they are not unsafe for the unborn baby. These things fall into the category of ‘weigh up the pros and cons’ and should be decided on a case by case basis depending on the woman’s individual presentation, including her pelvic floor, joints, muscles and connective tissue.