All you need to know about exercise in early pregnancy

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Is it safe? Will it cause a miscarriage? These are probably the top two burning questions that pregnant women have about exercising in early pregnancy.

I have first hand experience of this - I’ve had 3 miscarriages now but also (thankfully) 2 beautiful babies - and in some cases I have exercised a lot during early pregnancy, and in other cases I have purposefully stepped aside from my usual routine, and have limited my exercise to walking daily...and for me, it hasn’t made any difference either way. So let’s talk facts...

Pregnancy Exercise

According to the American Congress of Obstetricians and Gynecologists (ACOG), if a woman has an uncomplicated pregnancy she should engage in aerobic and strength-conditioning exercises before, during and after pregnancy. The American College of Sports Medicine (ACSM) suggests that 'moderate to hard' is quite safe for a woman who is accustomed to this level of exercise.

So you know that yes indeed you can exercise safely during your first trimester, but that last line that you just read is important “...for a woman who is accustomed to this level of exercise”. The evidence says that you should continue whatever your exercise routine is, if you are having an uncomplicated pregnancy, and make adaptations where required. But being pregnant is NOT the time to start a brand new fitness program which requires you to suddenly exercise significantly more than you are currently doing. However, if your current regime is zero, then you need to get up off your backside and start! But..start slowly. For guidelines on how much to do, where to start, and what is safe, read my blog on “What you need to know about exercising during Pregnancy”.

According to the research, there is no reason for a woman to postpone an exercise program if her pregnancy is progressing well from the start, is uncomplicated, and she feels good. In fact, it is now recommended that every pregnant woman exercises in all trimesters, even if she has led a very sedentary lifestyle in the past and is overweight.

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Helen Plass,

If you have been exercising regularly pre-pregnancy, then the research says, keep doing what you are doing as long as you are comfortable, and it's not part of the list of activities that you should not take part in while pregnant (contained in this blog). There is no research indicating that exercising in the first trimester causes a miscarriage. In general, women tend to feel better when they participate in low - moderate intensity exercise during the first trimester.

What’s going on with your body in the first trimester that may require adaptations?

  • In the first trimester, your blood pressure decreases and your heart is working a little harder - your heart rate at rest is up 15-20%. The volume of blood pumped out by the heart each minute (cardiac output), increases by 5-6 weeks of pregnancy. Therefore you may be prone to dizziness, a faster heart rate and that feeling of finding it hard to take a deep breath. Also you may feel you have reduced stamina and endurance
  • Pregnant women use more carbs during exercise, so in order to avoid dizziness, ensure you eat a small meal containing complex carbs, some protein and fat, 1 hour before exercise
  • The body’s core temperature increases (in early pregnancy, the concern is that increased maternal core temperature could results in fetal malformation). The growing baby depends on its mother for heat dissipation (temp reduction). Excess heat in the first few months of pregnancy has been linked to birth defects (39C /102F) – high maternal fever in early pregnancy (first 2 months) is linked to an increased risk of neural tube defects. E.g. sauna or hot tub. Repeated use of saunas and hot tubs for longer than 30 mins can have stronger risks. So it depends on how hot the hot tub is – there are too many variables to have an absolute to be safe, just don’t use them.

Therefore here is my advice for exercising while in the first trimester of pregnancy:

  • Keep hydrated and drink every 15 minutes
  • Eat a small meal 1 hour before exercise
  • Ensure you can comfortably talk during all forms of exercise - if you can’t, it’s a sign you are working too hard
  • Keep cool - wear layers which you can remove as needed, and avoid any form of overheating
  • Stick to what you know - you need to be at least walking daily, or a minimum 5 times per week, but now is not the time to start a brand new sport. If you are totally sedentary currently, build it up slowly from 15 minutes walk to 30 minutes walk over a few weeks
  • Listen to your body - are you dizzy, do you feel you are overworking, are you experiencing any cramping or pain? Then stop or slow down
  • Use your least-used sense of all - common sense! If something just doesn’t feel right, then your gut feel is most likely correct. Step away! At ANY point you feel unsure if everything is ok, go to your medical care provider to check


Something that is really crucial during your pregnancy, and being aware of this from the outset, is your posture. Are you aware of how you should be standing both during exercise and when normally carrying out your daily life? The over-arching of the lower back, and rounding of the shoulders and upper back, are postural issues which occur during pregnancy, and you really want to protect your back and whole trunk of your core before you grow bigger into the 2nd and 3rd trimesters. I did a big Facebook Live video all about the importance of Posture during Pregnancy and the implications it can have, so go on over to my FB page and check it out...

Recruit your TA!

Say what now?! You need to get to know your TA - your new BFF. The Transversus Abdominis muscle is so crucial to your long-term comfort during your pregnancy. Learn about it, where it is and how to engage it properly. It’s your deepest core muscle and provides a million important functions during pregnancy and birth - namely keeping your entire trunk of your body strong and supported (your back, pelvis, abdomen, pelvic floor...), and therefore reducing an potential pain in the body. It also is responsible for helping to push the baby out! It’s very important to ‘recruit’ (engage) this muscle during your exercise.

<p>Transversus Abdominis</p>

Transversus Abdominis

Is intense exercise safe in the first trimester?

Well, this is a little tricky as “intense” might mean different things to different people! I prefer to use the term ‘all-out’ or your ‘maximum’ exercise intensity. You need to talk with your doctor first off and discuss your overall health, your medical history, and what the current status of your pregnancy is, before you contemplate working to your maximum effort while pregnant.

James Clapp has done a significant amount of research relating to exercise and pregnancy. He would say that pregnancy is not the time for a rapid increase in exercise frequency, for all-out sustained effort, nor for middle-long-distance competitive events.

There are some small studies which indicate that when a pregnant woman exercises to her maximum intensity, they experience a 12% decrease in uterine blood flow. But a ‘fetus does not suffer from a reduction in oxygen consumption until the blood flow to the uterus decreases in excess of 50%, which is a number far greater than the 12% noted in studies’. That said, intense/all-out exercise during pregnancy is not something I would feel comfortable promoting. In reality, there just isn’t enough evidence out there to prove that prolonged, strenuous exercise in pregnancy is safe.

So if it were me, I wouldn’t be aiming to work anywhere near my maximum effort during my pregnancy. But I strongly urge you to exercise safely at all stages of your pregnancy as it will have a profoundly positive impact on your comfort levels, your delivery and your recovery!

Helen Plass, owner of, is a Pre & Postnatal Fitness Specialist, and Yoga Instructor, working with women to achieve a kick-a*s Pregnancy & Birth, leaving the pregnant mama feeling strong, super confident, and looking forward to her birth! Through her combination of specific prenatal Exercise, Yoga, and Active Birthing principles, Helen enables women to enjoy a happy and powerful pregnancy! She’s a proud mama to two energetic little boys, former corporate marketing professional, keen runner and lover of all things related to sport…and is an avid supporter of Irish Rugby.

Go to to sign up for her weekly tips, videos, interviews and to check out her online Pre- & Post-Natal courses.

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Helen Plass,