1st Trimester: What to Expect from Running When You’re Expecting

What to expect from running when you're expecting
Jeff Forman/JForman@News-Herald.com

As I write this I’m just weeks away from delivering my third child. I’ve run through all of my pregnancies to varying degrees and because I know how hard it can be to find reliable information on running while pregnant I want to share with you what I’ve learned over the 26 months of my pregnancies.

So today I bring you the first of three installments of my guide to running while pregnant. This post chronicles the first trimester and tells you what you might experience with your running during that period.

Because every woman’s pregnancy experience is different, I know I can’t cover everything and might miss something important to you. I encourage you to ask questions and offer suggestions for other topics to cover. And as always, if you experienced something different or disagree let us know that too!

Now on to The First Trimester!

Weeks 1 – 4 (Blissful Ignorance)

3 weeks pregnant with my second and on my way to winning a marathon, albeit with a much slower time than I expected!

The first two weeks, you’re technically not pregnant. You are getting ready to ovulate and then ovulating. But around 2 weeks in, fertilization occurs and the little zygote starts burrowing into the uterine lining and starts to release some exciting hormones. You probably won’t notice anything different, unless perhaps you race or do a really hard effort during this time.

I ran a marathon when I was unknowingly 3 weeks pregnant with my second child. I could not for the life of me understand why I was running so much slower than the pace felt. I thought for sure I was running around 7:15, but was running more like 7:30+ over the last 10 miles.  When I was about 4 weeks pregnant this time, I did a speed workout and my lungs burned at a pace that should have been more than doable. I thought I was just out of shape from taking time off to nurse an injury. I was wrong!

Once implantation occurs, those hormones trigger your body to make more blood, which in turn taxes your cardiovascular system more than normal. But it’s a subtle difference in those early weeks and probably only detectable when we’re really pushing ourselves.

My training logs for my first month of my 3rd pregnancy:

Week 3

Week 4

Weeks 5-9 (OMG! I’m Gonna Die!)

You might not look that pregnant at 7 weeks, but if you’re like me you’ll sure feel pregnant!

This is when the fun really starts! At 5 weeks you might feel a little extra breathless on the run – it might be hard to hold a conversation with your running buddies as you huff and puff.

If you are one of the lucky ones who experiences morning sickness, (which is in reality all day and night sickness), it will likely hit you between weeks 6 and 8. If you make it to week 8 and still feel pretty good, consider yourself one lucky lady! Morning sickness is no joke. Besides the constant nausea and bizarre food aversions (I seriously ate next to no fruits or vegetables for 3 weeks this time. Gross!) you might also suffer from very severe exhaustion.

While the baby is a mere speck at this point, the hormones are wreaking havoc on your body.Your body could probably run pretty close to your PRs right now, if somehow you felt like doing it. But it is really hard to muster up the energy to get out of bed, let alone get out the door for a run, let alone run hard!

And there’s something else that makes running difficult during these weeks:  you might be experiencing anxiety about miscarriage or something going wrong with the pregnancy. It can feel scary to push yourself physically when you know such a fragile process is going on inside your body, and it’s hard to justify that track workout when the speck inside you is so dependent on you taking care of yourself.  No matter what any doctor or book says, no matter how many friends-of-friends ran 10k prs at 6 weeks pregnant or continued to run megamiles, it’s all different when it’s your health and the health of your baby at stake.

For me, all physical signals said STOP. LAY IN BED! And it was hard to ignore them with motherhood on the line.  That being said, all scientific evidence points to exercise as being not only not harmful to the developing embryo, but also downright good for both of you.

[pullquote]Every day is different. One day you might not be able to get out of bed and the next you might feel like busting out a track workout. Take each day for what it brings you and roll with it![/pullquote]

How much you do during these weeks is up to you and your doctor. You needn’t worry about overheating (unless you’re running in some crazy hot weather) or how high your heart rate is. The main thing is to stay hydrated and stay within an effort level that feels comfortable. That doesn’t mean you have to run easy 24/7, but when you do push it you probably want to avoid running so hard you get out of breath, nauseous or need to bend over with your hands on your knees after intervals. I felt good keeping things at about a tempo effort when I did workouts and races during this time and throughout my pregnancy. I did several track workouts during the first trimester and was about 1:00/mile slower on 800’s, etc. and I also felt like 2 – 2.5 miles of intervals was about all I could handle, when I usually did 3 – 5 miles of intervals when not pregnant.

Especially during this month, every day is different. One day you might not be able to get out of bed and the  next you might feel like busting out a track workout in between going to work and cleaning the house. It’s weird how bad one day can be and the next day is not so bad. Take each day for what it brings you and roll with it!

My training logs for my second month of my 3rd pregnancy:

Week 5 (no log, but according to daily mile I ran 50 miles before finding out I was pregnant at the end of the week!)

Week 6 (no log again, but managed 47 miles)

Week 7 (no log. Fell off the cliff: 35 miles)

Week 8

Week 9

Weeks 10 – 13 (Feeling Alive Again)

Getting ready to head out for a 5k while 10.5 weeks pregnant with my third. I ran 20:47, 2:32 slower than my PR but it felt good and I was happy with it.

As the first trimester winds down you will one day feel sudden relief from the morning sickness and the fatigue. For me, I typically felt one level better around 10 weeks. During this pregnancy I had a horrible puke-filled day at 10w3d, but on 10w4d I felt good enough for a 4th place finish in a local 5k and haven’t puked since.

By week 12, I felt good enough to start running a little more all three times. This third time I ramped all the way back up to 45-50 miles per week around week 13 and held steady until about 20 weeks! Also, the risk of miscarriage goes way down once a heartbeat is detected after 10 weeks. As a result, your anxiety will probably ease up and make running more enjoyable in that regard as well.

This is the beginning of the good times of the pregnancy when running usually feels pretty great.

My training logs for my third month of my 3rd pregnancy:

Week 10

Week 11

Week 12

Week 13


Want more? Read our 2nd Trimester: What to Expect from Running When You’re Expecting

What was your experience running through the first trimester? Did you experience morning sickness? Do you have any questions or concerns about running during the first trimester?

➤Like Salty Running on Facebook or follow us on Twitter!

Salty Running boss and mother of 3 little ones with PRs of 3:10:15 (26.2), 1:25:59 (13.1) and 18:15 (5k). I love to write about running culture, mental training, and fitting in a serious running habit with the rest of a busy life.

Leave a Reply to Kim Cancel reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.


  1. GREAT article! I love that you are bringing attention to this topic as there isn’t a lot of good information out there about it. I ran during both of my pregnancies, and I feel very passionately about doing the best you can to stay active during pregnancy. I was fortunate to have healthy pregnancies and get the green light from my doctor to continue running. I believe that it helped me to feel good during pregnancy and get back into running fairly easily afterwards.

    I had similar experience during my first trimester. I remember going out for a 10 mile run before I knew I was pregnant with my first and just feeling sluggish for no good reason. When I found out I was pregnant it all made sense. I had bad morning sickness both pregnancies, so running during the first trimester was difficult. What I did find though was that I generally felt better while I was running – the key was that I just had to motivate myself to get going. It also helped me to drink water every mile (not something I usually do, but I found more frequent small drinks worked better). My morning sickness subsided around 11 weeks, so I was able to return to a somewhat normal running schedule at that point.

    I can’t wait to read the other installments of this article!! One other topic that is specifically of interest to me is breastfeeding and running. There isn’t a lot of information out there on this either, and I’ve especially found it challenging to try to fit in long runs while nursing my six month-old.

    And how awesome is it that you are able to say that you WON a marathon while you were pregnant?! Amazing.

    1. Thanks, Marie! That’s such a good point about how, even on the worst morning sickness days, you feel remarkably better once up and running. And we’ll be getting to breastfeeding! My friends all think I’m a hippie because I’ve nursed both of my kids until 2 years old, but after all that experience I like to think I know at least something about training and nursing 🙂 Thanks again!!!

  2. This is a great article, but I must ask a personal question. How the hell did you manage to get a monthly period while training for marathons? I’ve been running marathons for the past 5 years, at a respectable pace (3:32 marathon), though not as fast as yours, and I did not have a monthly cycle for 3 1/2 years. I had to recently give up running in order to try to conceive, per my doctor’s orders; my body simply would not produce a cycle. Only now in the past few months have I started to get cycles again. I’m just perplexed, because this is often the case for women who log many miles, and your definitely meet that qualification.

    1. Everyone is different in what their bodies will tolerate before shutting down the reproductive system. It might be the training or you could have some other underlying menstrual/ovulatory disfunction, so it’s really hard to say. I have never lost my period from training, even running as many as 80-90 high quality miles in a week. I will say that I have signs of a luteal phase deficiency during peak training – my cycles get shorter and I have intermittent spotting after ovulation, but I’ve never stopped ovulating or menstruating from training. In fact, I was running 50 miles a week and nursing my infant and got my period back at 3.5 months post-partum! UGH! My cycle seems to be pretty hardy 🙂 I will say that all three times I’ve gotten pregnant, I was 1) in a down-phase from training and running minimal mileage; 2) tapering or 3) injured and not running. I was up 3-7 pounds from my low “race weight” all three times and I’d bet it’s not a coincidence.

      Anyway, this is just my experience. I think not getting a period is the exception and not the rule. I haven’t done a formal survey, but just based on my training partners and friends I know very few people (if any, actually!) who do not get their period even running 100+ mile weeks. Something’s going on in your body that either makes it very sensitive to your energy output or there’s something else going on. We’ve written about amenorrhea here: https://www.saltyrunning.com/2012/08/27/completing-the-female-athlete-triad-spotlight-on-amenorrhea/

      We definitely plan to post a series on training and trying to conceive as it’s a really tricky subject. There’s not a lot of good information out there and it seems like when a woman is having trouble conceiving and she’s a runner, the running is almost always blamed. However, it might not be the running at all! Clove wrote about this a bit here: https://www.saltyrunning.com/2012/05/31/stroller-jealousy-the-life-of-the-infertile-runner/

      I wish you all the best on your TTC journey and do hope you’ll keep us updated! Thanks so much for the great question!!!!

      1. Thank you so much for your response, as well as the links to the other blog posts.

        I’ve been to a few doctors and fortunately my hormones check out normal, but as you suggested, my body uses a ton of energy when I run; thus, resulting in a cycle shut down. I have to admit, it’s great not having a cycle when I’m training for marathons, however, I realized there are some downsides to it. I am taking a year long break from running (*sigh*) and put on 10 pounds (*double sigh*), but oddly enough, I’m happy to have Aunt Flo again (though I forgot how incredibly annoying and painful they were). As you also noted, I now noticed that I have a one week long luteal phase, which is also a problem. It’s all about tweaking things at this point.

        I really miss running, but have substitute it with other things, like elliptical and weight training.

        We’re giving it one year, and then will give up. If it’s meant to be, then it will happen, if not, then so be it. I’ll keep you updated on my progress. Thanks again!!

  3. Hi Salty! Thanks so much for posting about this. My oldest sister had a miscarriage a few years ago and the doctor restricted her from running when she got pregnant the second time. This time, the result was a healthy, happy baby girl – Mollie! It’s hard to say if running contributed to the miscarriage or if the body just didn’t take, but I think this is a very pertinent topic among female runners! I’m thinking of you as you get SO close to delivering the babe!!!

    1. From what I understand, almost all miscarriages have nothing to do with what a mother does. They’re usually something that will happen no matter what the mother does – e.g. something happened when cells were dividing, chromosomal abnormalities, etc. At the same time, as I said in the post, I think once you go through a miscarriage or anything that reminds you of how fragile the process of making a baby is it’s really hard to do anything that might even have an extremely remote chance of jeopardizing the pregnancy. It’s easy to say running won’t have any affect on the pregnancy, but another to actually go out and do it when we’re worried about the pregnancy! I am so glad your sister had a healthy baby!!!

  4. Great article. Your attention to detail is terrific. I only started running 6 months ago, and now I’m 5 weeks pregnant. The week by week breakdown is seriously comforting. Thanks again!

  5. Thank you for posting this information . I have just found out I am pregnant again after a miscarriage this past Jan and plan on continuing to run albeit at a relaxed pace. There is scant info out there from actual runners who have trained throughout their pregnancy. Like you said running does not cause a miscarriage. It is usually caused by genetic abnormalities which you have no control over. Sometimes there are maternal blood clotting issues or immunity problems but please don’t think it can be cause by running and listening to your body.

  6. Thanks so much for sharing your story. I am 4 weeks pregnant and was planning to run a half-marathon at about 10 weeks. One of the few people I have told is super anti-exercise and is making me second guess myself. Running feels really great right now, and I am enjoying running while I can extra because I know I will have to stop at some point. I guess I will just keep listening to my body and see what insight it has instead of captain anti-exercise.

  7. Hello,
    Thank you for your experience with running during pregnancy. I am 11 weeks today and still worry so much that I have not been running regularly 🙁 too hard when working all day then the dreaded afternoon evening sickness kicks in. I was wondering about your thoughts on not letting your heart rate get above 140 during exercise? Everything I read says to keep it below 140. This seems crazy as I am running at such a slow pace to keep it under. Just wondering how you monitored your heart rate, or if you did at all?
    Thank you 🙂

    1. Great question! The 140 bpm limit is old news. Most obs recommend going by effort. If it feels easy, then it’s fine. You can even do moderate intensity from time to time like a moderate uptempo run. I sometimes did a faster mile here or there and even did some track workouts during my last pregnancy. I also raced a few times. I wrote about racing while pregnant and this post talks about running at a higher intensity than easy during pregnancy and might be helpful to you to feel better about disregarding the 140 bpm nonsense. https://www.saltyrunning.com/2012/05/10/racing-while-pregnant/

      Anyway, congrats! Keep us posted on how things go!

  8. Thank you for your prompt response 🙂 I think I am going to go with my gut from now on, if I feel that I am pushing too hard I will back off. I am worried that I may have already lost some of my fitness from not exercising regularly and not running my normal pace for the past 6 weeks due to the sickness and fatigue 🙁 but I will see how I go I guess. Thank you again 🙂

  9. love the site. Planning to run in the broad street 10mile in Philadelphia May 4th. I will be around 9 wks. My only concern which I have already spoken to my ob about is has anyone felt more lightheaded or faint due to the workouts more the day after a longer run?

  10. Question: I’m 11 weeks and just started feeling like getting back into a running routine again! However, my group runs at 5:30am just aren’t happening since I’m so exhausted! So I started running. Pushing my twin 4 year olds and am feeling great! I missed running! All was well until I took my temp after today’s run- (72 degrees and beautiful at the start of 3 miles) it was 101! I freaked and it took all my running joy away! Did you track your temps while you were pregnant? When do I start worrying – it’s just going to get hotter! Is it possible is overdid it without feeling it?

  11. Love this post! I’m 8 weeks pregnant with my second and feel a bit of relief knowing that I’m not the only one who feels like I’m going to die in this first trimester! It’s been a rough week, but I’ve been feeling much better as of yesterday and more hopeful to increase my mileage again or at least my pace! I’ve kept running through these rough weeks, but they are “survival” miles rather than enjoyable miles 🙂

    I raced a half marathon at 4 weeks pregnant with this baby, in my blissful ignorance phase. I gave that race all I could, yet I finished a few minutes short of my goal time – then I found out we were pregnant. Growing a baby sure takes it out of your body!!!

    Amy @ http://www.livinglifetruth.com/

  12. I am an a competitive marathon runner as well. I was 5 weeks pregnant and I was told by my doctor that I didn’t need to do anything differently in regards to running as long as I listen to my body and felt ok. However, I ran 10 miles this past weekend and felt ok during the run, but as soon as I got back home I experienced bad cramping and bleeding and I miscarried. I am not sure if it had to do with the run, but since it happened right when I got done with a longer run, it seemed like it may have contributed. I don’t think I will be running more than about 5-6 miles in my first trimester if I get pregnant again.

  13. I’m 6 weeks pregnant and really enjoyed a tentative and steady 4 mile run two days ago. I started feeling a twinge after abt 3 miles in my abdo which hurt on palpation. I’ve since had more twinges and slight spotting with dark gooey discharge. Has anybody got any advice. Obviously I want to be careful but if it’s merely a coincidence I don’t want to be overly cautious and stop running.

    1. I had some slight red spotting at 5.5 weeks with my first and I was very cautious, waiting a couple of weeks before resuming running. I think we had an ultrasound that made me feel better. One thing to keep in mind that my midwives told me that helped me with anxiety was that during the early weeks the pregnancy is either going to stick or it won’t and running won’t make any difference in that. Even so, it’s hard sometimes to believe that. So really, the best thing you can do is to trust your gut and talk with your doctor or midwife and figure out what you are ok with doing. You can always take some time off now and resume running later too. There is no right or wrong one-size fits all answer here! Hope your pregnancy is healthy and enjoyable!

  14. Thanks for your reply – it’s very reassuring. I think you’re right about pregnancy carrying on or not regardless (within reason). I’ll give it a couple of weeks and try again. I did go to the doctors today who advised not to be put off and carry on running! Thanks again. X

  15. Hi! I am a (somewhat) competitive marathon runner for my University. I just qualified for the national race and had a goal of beating 3:10. I just found out I am pregnant… we are so excited! I am not so excited, however, about the possibility of having to give up this race. I will be about 8 weeks at the time of the race which to me seems like it would still be fairly early in my pregnancy. I am not too concerned about the intensity because I never feel like my heart rate gets too out of control during longer races. My biggest fear is that the race is in the south during the summer…meaning it will be HOT. I live in Arizona, so most of my runs are done in the heat too. Is it too risky to keep training and go for it? It will be my last chance to race for the school.
    Any advice helps!

    1. Hi Chels, I’m in a similar situation to you. Was running marathon times around 3:10 last year as well, and have just found out I’m pregnant (with a marathon in a month)! I’d really like to do it, and unlike you, I would be able to take it easy, it is a big marathon and I won’t need to go hard. I didn’t think it seemed like a big deal, but I have been reading that most people would advise against running a marathon while 2 months pregnant. Did you end up running? How did it go? I really want to run it!

      1. If you’re trained for it then it should be fine (call your doctor and discuss tho first!) I think the biggest impediment will be whether you feel up to it. 6-12 weeks is when most women feel their worst. Hopefully you won’t feel terrible but you might. I’d just stay open minded about it and see how you feel as it gets closer. Good luck and CONGRATS!!!

  16. Thanks for the article. I have searched everywhere on the web for useful information about running and pushing yourself while pregnant, and you really addressed many of my concerns!

  17. I’m a few years late but I’m so glad u found this post!
    I took up running this year and I have my first long distance run ever in June 2015 (10k). Towards the end of this month (May), when I should be getting faster times, I’ve been struggling.
    My period was due earlier this week however I had nausea at the weekend and felt very fatigued. I managed a 7k with my hubby at a very slow pace – feeling exhausted after and spent most of the day lying down! The nausea continued the next 2 days. Yday (Tues) I took a pg test which showed negative. Maybe I was too early taking it.
    Well today I’ve just got in from my worst run – under 3k. My pace was slow and I began to feel nauseous again, I had to walk back home… I’m thinking to give it sometime and wait for my period before I get back on it, incase I find out the test was a false negative. I’m just concerned if I’m not pg, what might the reasons be for me feeling like this 🙁
    Any other recommendations? X

  18. Your Article was amazing! I loved to hear that you can run when your pregnant I just found out I’m 5w6d and every Hispanic in my family was like you can’t run anymore your pregnant but I love to run its my hobby I said it’s a myth that you can’t run when pregnant cause you can loose the baby but seeing you made me more certain of what I can do and I know I can do this!!! Thanks for this post!!

  19. I am so happy that this article exists. I am keeping this close to me the next few weeks as I may need it… 🙂 Bridget told me you got pregnant right around the time of the Towpath, and it looks like our luck is very similar!

  20. Wow. This is so helpful. I’m in week 7 now and I’m pretty new to running (about 6 months under my belt and still trying), but I was easily knocking down 5 miles/run up until a few weeks ago. I have been so disheartened that I am STRUGGLING to get in 2 miles right now and I had no idea why it was suddenly so hard. I knew I was preggo, but figured the 1st trimester would be no hassle. I’ve been strangely clumsy and slow. Thank you for posting this. I was on the verge of just calling it quits for the long baby haul but I’m gonna keep at it. I really, really needed this info.

    1. I’m so glad this helped! I felt the same way around that point. In about a month you’ll start feeling like running more again, probably! Hope so! Congrats and keep us posted how it’s going!!

  21. This is excellent information … I am 6 weeks pregnant and had been trying to get back into running after recovering from a knee injury… It was frustrating and hard and I was very inconsistent … Now, I just want to run but I have settled for ‘jogging’ at a slow snail pace and just for 30 mins at a time … The challenge for me is letting myself be OK with that and not comparing myself to what I used to do very easily.. I have had shocking nausea, no energy and hell headaches but it helps when I ‘jog’.. Although I do feel a bit dizzy and numb when jogging so I just run laps at a park and stop when I need to.. It’s good for my mental health, I really do get bored walking.. Hoping I can just get through the first trimester unscathed and relax a bit about whether little bean is going to really stick..

  22. Hi there, I know I am writing this well after you posted but I am in a similar position as you. I workout and train hard and when I do, I sometimes notice intermittent spotting and shortened luteal phase. You said you took a couple of weeks off when you were 5wks pregnant and noticed spotting, how hard was it to get back into the swing of training after that?

    1. I’d be interested in hearing about this as well. I’m pregnant again (about 7.5 weeks) after miscarrying last year. I had a tiny bit of spotting last week and my doctor put me on a week of bed rest. After I went back and everything was fine he said I shouldn’t run for another month!! This will be the longest I’ve gone without running since I had knee surgery over a decade ago. I’m worried about getting back in shape, especially since I will be trying to do it in the second trimester. Any tips?

      1. I eased back in with run-walks as I felt comfortable. I ran pretty slow through that first pregnancy – I was nervous but it could have also been from taking that little bit of time off. You can definitely run again (if doc says so) just ease in and as always, listen to your body. It’s ok to elliptical, walk or do yoga or whatever for 9 months if that’s better for you too. So make sure not to feel like you *should* run through your pregnancy if you don’t feel like it for whatever reason. Good luck! Keep us posted 🙂

  23. Did you feel it was harder in your second and third pregnancy to keep running? I had back surgery in March was practically immobile from feb-April when I got pregnant with my second. With PT and nerve medication I was able to return to working out, but running still seems so uncomfortable(like everything isn’t secured in there). I hate to miss out on running for so long, but I feel like I get menstrual cramps when I try to run even a short distance on the treadmill(I live in SC and June temps are over 100 most of the day, so running outside is out of the question). I don’t know if it’s psychological(I’m afraid of causing more damage to my back) or if it’s common to have more issues with #2.

  24. Thanks for adding in details about how much slower you were. I’d like more of those details and expectations too!

  25. Thanks for all of this detailed information! I am currently 5.5 weeks pregnant. In June, a friend and I signed up for the Hot Chocolate 15k at the end of October. I ran a half marathon at 3.5 weeks and walked two miles. I texted my friend in the middle of my walk (who had, unbeknownst to me, set her own PR and already finished) apologizing for making her wait. I cried all night because I did so poorly in the race. The next day, I found out that I was pregnant, and all of the tears turned to happy ones (and a few ‘I’m hungry, feed me’ ones as well). Now I am debating on whether I can run the Hot Chocolate 15k. I’ve run a total of 6 miles in the past two weeks, partially because I’ve been resting from the half, and I am trying to tell myself I can do 5 miles tomorrow for training. This race, I might have to sit out though. At least it’s for a good reason!

  26. I just found out yesterday I’m 7-8 weeks…..I had no idea. I’ve been training for a half marathon on Sunday and it has been feeling tough for the last 2 weeks. Only thing is I’m now really worried as I live in Africa and although I train mostly on the treadmill my sessions always leave me very hot. I’m not going to run on Sunday and I’ve switched to walking for fear of overheating but what if the damage is already done?

  27. Thank you SO SO much. I have been needing a detailed breakdown like this! We have been trying to get pregnant, and every month I’m scared that my running is hurting our ability to conceive, despite endless reassurance from my doctor that it’s okay. This gave me a great idea of what I can do to be sure I’m being healthy!!! Can’t believe you ran a marathon without knowing you were pregnant yet- that fact alone is hugely comforting!!! ??

  28. My heart rate is high normally and when I run it sometimes hits 200 bpm or a little over. I’m 5 weeks pregnant, run regularly, and have my first 5k pregnant on Saturday. Any advice?