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Muscle Gain During Pregnancy: What To Expect (Part 1)
Updated: Aug 12
Can you BUILD muscle during pregnancy? Part 1 - Women who already lift weights
Is this a reasonable goal during pregnancy? As always, the answer starts with “it depends” - MOSTLY it will depend on whether you are already trained or not.
So let’s first talk about women who are TRAINED - i.e. they already lift weights and have decent amounts of muscle mass, and you want to continue during pregnancy.
If you do not currently lift weights - whether you have NEVER lifted weights or if you haven't lifted weights for 6 months or more - and you want to START lifting weights in pregnancy (yes, it is absolutely safe to do that) - check out Part 2 of this blog post here.
You can either read the blog post below, or listen to the podcast episode on YouTube
In short, no, it isn't reasonable to expect to BUILD muscle during pregnancy. (Sorry, I know that’s not what you wanted to hear).
Ok, so here's the nuance - it IS theoretically possible to build muscle during pregnancy. But we have to first of all consider the main drivers of muscle growth:
mechanical load/tension (lifting weights that challenge the muscles)
progressive overload (gradually increasing intensity or volume over time)
and proper nutrition/recovery (supplying adequate protein and calories for muscle protein synthesis and rest).
Pregnancy presents several practical obstacles to achieving these aims.
Mechanical Load
There are physiological changes, like the secretion of certain hormones, during pregnancy that affect the elasticity of our connective tissue, decreasing force production in the muscles.
Think: if the connective tissue attaching the muscles to the bones are more elastic, the muscles have to work much harder to produce the same force.
There are also anatomical changes - like the growing belly, weight gain and hip stability that also affect our ability to produce force.
Practically, if you can produce less force, you are going to be lifting less weight. This produces less mechanical tension (the main driver of muscle growth).
And that's without mentioning other, very real symptoms of pregnancy - like fatigue - that can make training, especially lifting weights, particularly difficult. While it may be that = this experience is purely subjective- any woman who has experienced severe fatigue in her first trimester will tell you that it is a very real obstacle nonetheless and it is INCREDIBLY hard to override or simple "push through".
Other physiological changes to our cardiovascular system (the phenomenon of "underfill") also reduce our cardiovascular efficiency, effectively increasing your heart and respiratory rate while exercising. While this is normal and natural, if you're struggling to catch your breath during a set of squats and are limited by your cardiovascular system - you are going to find it more difficult to load the muscles sufficiently.
It's also incredibly common to experience fatigue after a workout. Many women find they have to limit the length (and intensity) of their workouts or they cannot get themselves through the rest of the day.
Many women also experience pelvic pain (SIJ pain, symphysiolysis, sciatica, groin pain) which can be very limiting for lower body workouts.
I know this list is depressing - but in my experience, lifters underestimate the impending physical (and sometimes mental) struggles of pregnancy, and do not plan accordingly (especially when walking into their first pregnancy).
Progressive Overload
If you are struggling to load the muscles, progressive overload is going to be difficult to achieve.
If you're experiencing fatigue, you may not be able to go up in weights (intensity), or training volume (load x reps x sets) sufficiently in order to DRIVE muscle growth.
And if you are ALREADY trained, already strong and pushing your limits in the gym, it's unlikely you will be able to continue to improve. Your pregnant self, with all the symptoms of pregnancy, may struggle to improve on the performance of your not-pregnant self.
(This is different to UN-trained women - women who are STARTING strength training during pregnancy - they usually have very little muscle mass, and are nowhere near their genetic potential. When they start training, they have "Beginners Gainz" to look forward too. Trained women have already exhausted their beginners gains and are now facing The Law of Diminishing Returns. The more muscle you have: the harder it is to gain.
You can of course manipulate other training variables like time under tension or reps and sets to increase overall training volume, and to compensate for the reduced load BUT your ability to recover will also likely be compromised during pregnancy.
Recovery and Nutrition
You can only train as hard as you can recover - and pregnancy presents several challenges to optimal, or even adequate recovery.
Struggles with sleep/insomnia, as well as nausea, aversions to certain foods, cravings and wacky hunger signals. This can all make it incredibly difficult to recover from intense workouts and get adequate nutrition.
You need to ensure you are eating adequate calories and protein during pregnancy to both fuel training and recovery as well as building a baby. Caloric needs don't change in the first trimester, but go up by about 300 calories a day in your second trimester, and around 450 in your third.
Protein needs should be calculated similarly to outside of pregnancy. 1.2-1.6g per kilogram of ideal bodyweight. (You should be aiming for closer to the top of that range if you are lifting moderate to heavy weights and want to optimize muscle building and recovery).
Since bodyweight will increase during pregnancy, protein needs increase naturally.
So if you weigh 65kg before pregnancy (1.2-1.6 x 65) you should aim to eat a MINIMUM of 78g protein a day and you should IDEALLY be aiming for 104g protein a day.
If your weight increases by 15kg by the end of pregnancy and you weigh 80kg, you should aim for a minimum of 80g a day and ideally closer to 128g protein a day.
This may sound very achievable if you are used to prioritizing protein in your diet, but let's not forget that your body is doing a lot of metabolic work literally building a human - so nutrient needs (including protein, fats, vitamins and minerals) all go UP, at the same time that you are experiencing nausea and food aversions (so likely struggling to get sufficient nutrients for pregnancy AND training). Reserves are low and training load and volume will likely need to decrease over the course of your pregnancy.
It's difficult to convey just how debilitating nausea can be. I am someone who eats a relatively whole-foods, protein-rich diet. However, during my first trimesters (I've been pregnant 3 times) I had a severe aversion to protein rich foods like meat, chicken, fish, eggs and dairy - there were days where all I could eat were dry petit beurre biscuits or crackers. Even in my third pregnancy where I tried to convince myself it's just a mind over matter thing, and despite knowing just how important it was for both me and the baby, I just could not stomach anything remotely healthy.
It's important to note that these symptoms vary MASSIVELY from woman to woman. For some, they may be non-existent, for others they may be severe. Some women really do feel fine, or even great during pregnancy (some women actually report feeling better during pregnancy than they do normally) - but after a decade of working with pregnant and postpartum women, I have come to understand that they are unicorns - the exception, not the rule. You might be a unicorn, but you probably won't be. Most women find pregnancy physically and mentally hard. My conclusion after 3 pregnancies is you have to deal with the hand you get, do the best you can - and not compare yourself to others.
And also that reality often does not live up to expectations.
Maintaining Muscle Mass
Therefore, the goal should be to MAINTAIN AS MUCH MUSCLE MASS AND STRENGTH AS POSSIBLE. This should be the goal of your training throughout pregnancy. By maintaining as much as you can of the load and training volume that you were doing pre-pregnancy, as well as doing everything you can to ensure adequate nutrition and rest, you can hold onto as much muscle as you can.
Modify Before You Omit
This is the most important mantra you should adopt for your training during pregnancy: Modify before you omit.
This means that if you cannot squat what you were squatting before, reduce the weight, rather than just stopping squatting.
This works whether you can squat 100kg or 20. Reduce the weight to what you can do, pain and symptom free.
Even if that means doing bodyweight squats. You can also reduce the range of motion, i.e. doing half ROM squats or box squats rather than arse-to-grass.
If, for whatever reason, you find that you can't squat (knee or hip pain), replace it with a compound lower body exercise that you CAN do, like RDLs or Hip Thrusts.
If you find you can no longer do pullups, switch to an exercise that uses the same movement pattern, like lat pulldowns or single-arm pulldowns. Here's my blog post on how to modify pullups during pregnancy.
The same is true for every exercise - if you cannot do barbell shoulder presses, switch to dumbbells. You single arm variations.
And of course you need to modify around the bump. When you have a huge belly, you will not be able to do pushups on the floor, but you can do incline pushups and even bench press.
If you want to know more about what training should look like during pregnancy, join my "How to Train During Pregnancy" emails
You should also check out my online programme "Strong Pregnancy" which has a written pregnancy programme with modifications for each month of pregnancy. I also offer 1:1 coaching to pregnant women.
The "Diminuendo"
Therefore, as we progress during pregnancy as a result of of all of the (unpleasant or inconvenient) physiological and anatomical (and sometimes psychological) changes that happen during pregnancy, most women who lift heavy weights simply find that they cannot lift as heavy, as often, or for as long as they were doing before pregnancy. You should therefore think of this as a "diminuendo" as your pregnancy progresses.
And, incidentally, postpartum, you should start early and gently, and think of your training as a crescendo.)
With reduced load and volume, comes SOME muscle loss. Since it isn't reasonable to expect to load the muscles as much as before pregnancy, and since mechanical load is the main mechanism of hypertrophy, it will affect our ability to gain muscle while pregnant.
(although it may not be as linear as that - I, personally found that I had to MASSIVELY reduce weights and training volume in my first trimester, from about week 16, I was able to gradually increase the weights week after week, until 7 or 8 months where I had to start DECREASING lower body weights again (but this time, it happened gradually) while upper body stayed pretty much the same.
To put some numbers on this, before pregnancy I was squatting 50kg, in my first trimester I was either doing bodyweight squats or something like a 5kg dumbbell; in my second trimester I built back up to 40-odd kilos, and by the final week of my pregnancy I was squatting 27.5kg)
This is not the end of the world. You should still work hard to hold onto as much as you can, because it it much easier to maintain muscle than it is to build it! This will mean you will go into postpartum with as much muscle mass as possible, and you will have less work to do to regain the lost muscle and strength.
(not to mention that more muscle postpartum will help you avoid pain and injury, and cope with the physical demands of having a baby).
All-Or-Something Mindset
The main problem I find with women who lift heavy weights/do CrossFit is that they tend to have an all-or-nothing mindset around exercise - this holds them back far more than the actual symptoms of pregnancy.
Story time: When I did my training to become a pre-natal specialist 10 years ago, (2 years before I went through pregnancy myself) there was another woman there, about half-way through her first pregnancy.
She was the only other woman there who lifted weights (the rest did Pilates and Zumba and thought I was mental). She said to me "I had to stop lifting when I got pregnant - I just couldn't do it anymore. I was squatting 70kg before pregnancy, and I just couldn't lift that sort of weight anymore - so I had to stop"
I asked her if she had tried lifting LESS weight - I dunno, 60 kilos? 40? an empty barbell? just a bodyweight squat? She looked at me confused and said "why would I lift less weight? It doesn't do anything"
Ad THIS is exactly the mindset that plagues many women. So she chose to lift NOTHING and do ZERO SQUATS for 9 months (and presumably postpartum too, because I can't imagine she woke up one morning with the ability to lift 70kg again without training) instead of doing SOMETHING.
You have to get over this if you want results in pregnancy and postpartum. SOMETHING is ALWAYS better than NOTHING.
Going back to my example - at the end of pregnancy, I wasn't lifting what I was lifting before, but I was lifting almost 30kg on a regular basis. That's 3/5 of what I was lifting before. That is a huge success, and it set me up for a much better postpartum return-to-fitness that doing nothing would have. But most women struggle to see it that way.
If you struggle with this mindset piece, you should apply for 1:1 coaching with me - we work on nutrition, training AND mindset to help you reach your goals.
Pelvic Floor.
I've gotten almost to the end of this article on exercise and pregnancy and haven't even mentioned the pelvic floor yet.
A lot of the noise around lifting weights being "bad" for the pelvic floor is (like most women's health info online) oversimplified and out of date.
In a nutshell, lifting weights does increase intra-abdominal pressure and put "pressure" on your pelvic floor, but that isn't necessarily a bad thing - it's actually the way our pelvic floor is supposed to work (contracting against intra-abdominal pressure, and NOT doing an isolated contraction and lift, i.e. a "Kegel")
However, while you might be able to lift heavy loads, and while moderately heavy loads may be beneficial for your pelvic floor, lifting maximally heavy loads may no be.
Some training guidelines specific to lifting weights that you should consider if you are pregnant:
Some experts recommend exhaling on the EFFORT, rather than holding your breath and "bracing". This is probably a good guideline to follow if you are worried about your pelvic floor, but it will also reduce the amount of weight you are able to lift (which is a good thing if you're trying to navigate the middle ground and aren't pushing for as heavy as possible).
So you may choose to select weights that you can lift while EXHALING - this may help regulate intra-abdominal pressure and may help safeguard the pelvic floor.
Or instead, you can opt for training according to "Reps In Reserve", RIR of 1-3 reps, which means leaving a couple of reps in the tank, rather than maxing out or reaching failure.
You should NOT be experiencing pelvic floor symptoms like leaking or feelings of heaviness during pregnancy - and if you are, you should first try reducing the load and exhaling on the effort - that may be all that's needed to stop the leaking. You should also see a pelvic floor physiotherapist. You should also NOT stop lifting weights altogether - MODIFY BEFORE YOU OMIT - again, we can fall into all-or-nothing thinking very easily here.
Some guidelines recommend lifting in a higher rep range of 8-15 reps, rather that 5 rep maxes or 1 rep maxes- although it may still be safe to lift for 5 reps if you leave a couple in the tank, if you are an experienced heavy lifter and aren't experiencing any pelvic floor symptoms.
Remember that active women, especially those that lift heavy weights are more likely to have an overactive pelvic floor than a weak one. Physical activity strengthens the pelvic floor (just like every other muscle in the body). Pelvic floor symptoms like leaking or a feeling of heaviness can be signs of an overactive pelvic floor as well as a weak one, so kegels are not a one-size-fits-all answer to this problem. If your pelvic floor is overactive, you may need relaxation exercises rather than strengthening. How do you know which one you have? You should see a really good pelvic floor physio to find out.
Muscle Loss During Pregnancy: Mindset Shift
A final word about mindset - as I said before, it can be incredibly difficult for very fit women to accept the changes and limitations to their routine, and the prospect of losing hard-earned gains can be really scary. It's more than just heavy weights and muscle mass - it can be a really scary change or loss of identity. It is really important though to embrace the physical changes and to adapt to them. This might involve some grief and letting go (it did for me) but remember that pregnancy is temporary. If you train right, you can return to previous levels of strength and fitness, and remember, that proper (and safe) pregnancy exercise is your postpartum PRE-hab.
Conclusion
It is technically possible to gain muscle during pregnancy, but the practical realities of fatigue, nausea, food aversions, musculo-skeletal pain and a growing belly make it difficult to meet the criteria for muscle growth (mechanical tension, progressive overload and adequate nutrition and recovery). Therefore, a sensible goal for most fit and strong women is to maintain as much muscle mass and strength as possible. Our mindset can often present even more of a problem than the physical realities of pregnancy. Changes to body image and identity make this a challenging landscape to navigate. We should adopt a "something-is-better-than-nothing" mindset, modify before we omit and not catastrophize if our pregnancy training looks like a gradual diminuendo.
One of the best ways of combatting this is to follow a structured training programme specifically for trained women in pregnancy (not a generic prenatal yoga or pilates programme), with modifications and considerations for each trimester and month, like the one provided in my Strong Pregnancy Programme.
If you need more personal guidance, or help with nutrition and mindset, apply for 1:1 coaching.
If you want to know if it is possible for untrained women to build muscle during pregnancy, read part 2.
About Jen…
Hi, I'm Jen, and I've been a pregnancy and postpartum fitness specialist for the past 10 years. I'm passionate about helping women transform their bodies in a sustainable way.
I created Strong Pregnancy and The Complete Postpartum Programme, to provide sensible, realistic and effective workouts for this chapter. I run a 1:1 online coaching programme for mums where I help women lose weight, build strength and find habits that work in this chapter of our lives.
I have a reputation for my no-BS approach, my dedication to facts, science and evidence and for debunking myths around nutrition and exercise.
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