Pregnancy & Running By Trimester

Pregnant woman holding her belly and walking on a path in the park
October 18th, 2018 0 Comments

Evan Stevens

What to Expect When Expecting – As a Runner

You are fit, you are healthy, and you’re a runner. Sounds great – you have no problems, no worries, you can eat and do pretty much anything you want if you’re a die-hard runner. But what happens when you start to grow a new life within you?

Whether it’s planned or one of life’s great surprises, pregnancy means a huge change for you and your lifestyle. While running while pregnant was once thought to be controversial at best (if not otherwise downright taboo), it has become the norm for many expectant runners.

Pregnancy can be an exciting, scary, wonderful, stressful, and magical time; your body changes are amazing ways to accommodate the new human growing inside you. Some of these changes (most of these changes) are unwanted, I can’t imagine having to pee every five minutes being thought of as one of the joys of pregnancy (or so I’ve heard, having never been pregnant myself, nor planning on getting pregnant anytime soon – not to mention being physically unable to for that matter – who am I to judge). But do these changes force us to put aside running for nine months?

Running is an excellent way to manage your pregnancy, be it as a way to cope with stress, stave off gestational diabetes, reduce the risk of preterm babies, and even the need for a C-section. But your pregnancy is not a sprint, nine months is an ultra-marathon if there ever was one, each trimester needing to be taken as a whole new beast. This article aims to help you through each step of the process, what to expect with your running through each trimester while expecting.

Talk to Your Doctor First and Keep the Dialogue Open

This should go without saying but you should always consult your physician and OBGYN about continuing to run while you’re pregnant. Complications such as bleeding or placental problems should be immediately consulted and discussed with your doctor and running should be stopped immediately. But if you are healthy and there are no compilations, the risks or running while pregnant is minimal.

Related Article: The Stages Of A Woman’s Sleep Life: Pregnancy And Postpartum


There are a few safety precautions and things to consider before lacing up and heading out the door after you first hear your exciting news.

  • Avoid uneven surfaces: Your center of gravity changes as your pregnancy progresses so try to keep it on even, paved roads and paths or the rubberized track.
  • Stay cool: body temperatures too high (≥102) can harm the fetus and cause neural tube defects. Wear looser clothes and consider taking it inside in hot and humid temperatures.
  • Concentrate on staying in good form and running strong: Your body produces a chemical that causes you to stay loose and relaxed (it’s called relaxin). Your ligaments loosen up and can cause extra strain on your back and pelvis if you aren’t concentrating on keeping yourself smooth.
  • Drink lots of water: You can overheat easily (as mentioned) and you can lose a lot of water faster. Drinking a lot may make you have to pee that much more but frequent trips to the washroom are better than being dehydrated and depriving you and your baby of fluids.
  • You are going to slow down: there is no need to push yourself too hard. Take walking breaks, take extra recovery, and push your previous high standards out of your mind – this is new territory. You can still maintain fitness even if you cut back.

Now that we have some safety concerns and considerations out of the way, we’ll break down your running through each trimester.

First Trimester

Your first trimester is often your worst running-wise. Many expectant mothers face exhaustion and nausea which can make it exceedingly difficult to lace up and go for a run. But running, if you can force yourself to do it, can help with the exhaustion and nausea. Improved blood flow, endorphin release, and general movement help to prevent the exhaustion and nausea. There are some days where you may not be able to get off the couch, and that is totally fine! You are entitled to take some time to rest. As stated, you will slow down and your first trimester is usually when it happens.

If you do manage to bring yourself out there do be sure to take it easy. Keep your pace conversational and do not pay attention to your heart rate watch. During your first trimester, your hormone levels change significantly to ensure your uterus can support the fetus. Elevated heart rates are one of the most common side effects of being pregnant and it is totally normal. To support growth your body pumps more and more oxygen-rich blood through your body to feed the placenta and the baby.

Your first trimester is imperative for your baby’s neural growth. Eating properly is hugely important to who are you. I know as runners we like to manage how we look and weigh but you are more than yourself. Don’t be afraid of taking it easy and ensuring you are eating and recovering. Enough folic acid and sufficient caloric intake will ensure a healthy mom and babe.

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Second Trimester

Often called the “honeymoon” of pregnancy, the second trimester is often the most comfortable. Nausea usually subsides and energy levels return to normal. The biggest change here is that women will start to “look” pregnant. As the baby grows, so too will your stomach, stretching out to accommodate the forming life. Weight gain and appetite desires accelerate, which you should indulge in (so long as it is healthy).

Some mothers feel so great during this time in their pregnancy that they actually start to increase their mileage again and push the pace. And as long as you and your doctor agree that there is no problem with it, you should be good to go. You will still be slower than where you were pre-pregnancy but there are so many mothers who say how wonderful the second trimester is. It’s not surprising given how much-oxygenated blood is getting pumped through your body at this point; larger stroke volumes, more powerful, faster heart rates, and just generally more blood flow means more energy is readily available.

Now, with things growing and stretching it can bring on some new and different pains and irritants. Your joints tend to loosen up more and ligaments lose some of their “tautness”, especially in the back and pelvis. This can cause pain through the sacroiliac joint (SI joint), where your iliac bones (your large pelvic bones) attaches to your sacrum at the base of your spine. As your belly expands, it pushes your pelvis out and back, pinching some of the nerves at your back and through your SI joint and can cause some nerve pain radiating down your leg.

The Importance of Core Strength

The easiest way to ensure that the honeymoon remains sweet and pain-free is to have a strong core before and during pregnancy. A strong core alleviates the pressure on the back by keeping everything tight, preventing too much pelvic expansion.

The second trimester is also where gestational diabetes can come into play and when most doctors will test for it. If you have stayed fit and continued running, the risk of gestational diabetes is minimal because of the beneficial effects that exercise has on clearing blood sugars.

Related Article: Postnatal Core Exercises

Third Trimester

The third trimester is the home stretch. You usually naturally feel like cutting back running; be it because you start to feel too big or because things are getting a little sorer. And it is totally normal to not want to run through your third trimester; most healthcare professionals advise against it in fact. Running is a relatively high-impact form of exercise with a lot of weight going up and down. Without strong pelvic floor muscles (what keeps your organs inside you), a six to nine-pound baby, along with a placenta and added baby weight, going up and down in there can cause some unpleasantness. It’s already stressed enough with the extra 20 or so pounds that have been added in the past 6-8 months so there is no need for additional jarring movements.

But that doesn’t mean you need to stop exercising. You can still stay fit with non-impact cross-training exercises. It is a great time to swim – it takes a lot of pressure off your joints and allows for a greater range of motion than you get from your normal routine.

Yet some people still run. Alysia Montano famously competed at the US championships 8 months pregnant in 2014. The next year she came back to win the whole thing. Then she did it again in 2017 (although she was “only” 5 months pregnant then). The keys are to listen to your body and listen to your doctor. You will probably see a lot of your doctor in your third trimester so it is a good way to keep the lines of dialogue open about your running (if you still feel like doing it).

Returning to Form

After you’ve given birth it may be several weeks until you can (or want) to return to running. You just pushed a life out of you, and that life is going to be up all hours of the day and night. It is okay to take some time off, rest, try to sleep, and develop some form of routine. You need time for your tendons and ligaments to tighten up again before you run. You can still stay fit if you are a die-hard fitness buff; low impact work that you did during your third-trimester work exceptionally well and core exercises (planks, glute-bridges, etc.) are a great way of easing back into the thick of things.

It is important to be patient and not get frustrated with a slow build up. Keep up the nutrition; lots of vitamin D, calcium, and hydration, for you and your baby and take lots of rest. Your hormones are still in overdrive and breastfeeding can take a lot out of you. (It is also time to get a post-pregnancy sports bra – something supportive and properly fitted to ensure you are able to run in comfort again.)

Running (and exercise in general) is also a great way to deal with postpartum depression symptoms too. It can improve quality of life scores and if a mother is able to find a group of other young mothers, creates a social group during an otherwise isolating and stressful time.

Take Home Points

  • Always consult with your doctor about running while pregnant however and keep the lines of dialogue open throughout your pregnancy.
  • The first trimester sucks for running as you are often tired and nauseous. Running can help mitigate a lot of the side effects.
  • The second trimester is often great for running. No longer nauseous or tired, you can push yourself little more with the new found energy.
  • The third trimester is when most runners will slow down and take it easy, doing non-impact exercises to stay healthy (exercise can still help with pregnancy and feeling great even in your third trimester).
  • Some people can continue to run through their third trimester if their core is strong enough and they have talked to their physician.
  • There is no pressure to return to running immediately post-pregnancy – you are entitled to relax and recover.
  • Be patient.



Campolong, K., Jenkins, S., Clark, M., Borowski, K., Nelson, N., Moore, K. and Bobo, W. (2017). The association of exercise during pregnancy with a trimester-specific and postpartum quality of life and depressive symptoms in a cohort of healthy pregnant women. Archives of Women’s Mental Health.

Kramer, M. and McDonald, S. (2006). Aerobic exercise for women during pregnancy. Cochrane Database of Systematic Reviews.

Kuhrt, K., Harmon, M., Hezelgrave, N., Seed, P. and Shennan, A. (2018). Is recreational running associated with earlier delivery and lower birth weight in women who continue to run during pregnancy? An international retrospective cohort study of running habits of 1293 female runners during pregnancy. BMJ Open Sport & Exercise Medicine, 4(1), p.e000296.

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