The first trimester: Should you be exercising?

Posted on November 17, 2011

(Last Updated On: November 17, 2017)

The first post of this series was The first trimester: How much should you be eating?

This is written with your average, generally healthy, mom-to-be in mind. This is not written for people with outstanding health conditions. I’ll have a quick write-up in a future post for those where exercise is contraindicated but this is not the place to get answers on those topics. Hit up your OBGYN for that.


When it comes to exercising, the first question most moms-to-be ask is if exercising is going to harm their baby ala “Should I even do it?” A lot of women actually stop exercising once they become pregnant due to fear of potential issues. So let’s address that first.

Cutting to the chase, this is a topic that has been extensively studied for at least the last 35 years. Over those years there has been barely anything suggesting one shouldn’t exercise while pregnant.

Here are some quotes from the Guidelines of the American College of Obstetricians and Gynecologists for exercise during pregnancy and the postpartum period:

“Despite the fact that pregnancy is associated with profound anatomical and physiological changes, exercise has minimal risks and confirmed benefits for most women.”


“There are only anecdotal reports that strenuous training may cause preterm labour.”

These quotes are from 2003. In 2007 there was a Dutch study, the only study mind you, saying there was an apparent correlation between strenuous exercise and the chance of having a miscarriage. A couple notes on this study before you freak the hell out:

-Strenuous exercise was defined as 7 hours or more of exercise per week. I have a fair amount of clients and know the exercise habits of quite a bit of people. I might be aware of 1 or 2 people right now who exercise for 7 hours, or more, per week. That’s a lot of exercise. I’d venture to say way more than anyone would recommend while pregnant.

-The study called people and asked them what their lives were like before they had their miscarriage. From what I can tell this is done for ethical reasons, but it’s a really subpar way of assessing somebody. People’s recall is notoriously bad and I can only imagine how bad one’s is after a miscarriage.

-Again, it’s pretty much the only study, out of hundreds, maybe thousands, finding a link between exercise and miscarriages. At least hundreds have found no link.

Another quote from the 2003 guidelines:

“In another study it was concluded that mean birth weight is substantially lower when women exercised at or above 50% of preconception levels compared with non-exercisers. Another study found no difference between birth weight of offspring of vigorous exercisers and those of sedentary women, whereas others even found an increase in birth weight. It appears, however, that birth weight is not affected by exercise in women who have adequate energy intake. Reports on continuous physical training during pregnancy in athletes indicate that such activities carry very little risk.”

Let’s break this down.

  • One study found women who exercised similar to before they got pregnant had lower birth weights.
  • One found no differences in “vigorous” exercisers,
  • and one found an increase in birth weight. Athletes, who would qualify as vigorous exercisers, are found to have little risk.

This is confusing as all hell. What’s the deal?

Here’s my take: In regards to some vigorous exercisers having no differences in birth weight and some having an increase: People vary widely in their hunger response to exercise. Some people exercise hard and barely want to eat anything afterwards. Others head over to Denny’s and get a lumberjack breakfast…at 9pm. I suspect this doesn’t change during pregnancy. Some women are going to be very hungry after exercising and some aren’t. Therefore, some women who exercise during pregnancy get heavier than others.

What’s the deal with exercise and your appetite?

This is further illustrated by the researchers stating women who have been found to ingest an adequate amount of energy (read: calories) have not been found to have issues. I bet this is why athletes, despite exercising at a high level, have not been found to have issues. Athletes are generally much more aware of their bodies and what their energy intake levels are, whether they need more calories, less calories, more fluids, etc. They are likely to ingest an “adequate” amount of energy when exercising while pregnant. In the end they don’t have issues.

What about that study finding the exercisers who delivered babies with low birth weights? (Found here: Neonatal morphometrics after endurance exercise during pregnancy ) In this study a group of recreational runners who became pregnant were looked at. These women kept exercising at at least 50% of what they were doing before they became pregnant. Unfortunately I can’t find anywhere that has the full text of this study, but as best as I can tell the difference between these women and women who didn’t exercise that much, if at all, was a birth weight difference of 310 grams. Or about 0.68 pounds.

About 220 of the 310 grams was attributed to differences in the amount of fat the baby had. I don’t think it’s too important to worry about your baby being shredded with a 6 pack when he/she comes popping out, but I also don’t think it’s too important to worry about whether your baby is 310 grams heavier or lighter. If you’re that worried about it eat an extra slice of cheese each day.

Again, I can’t find the full text of this study, and this is not an area of expertise for me, but this study is definitely not swaying me away from having my pregnant clients exercise. Nor does it seem to be influencing any OBGYN’s either. As per their recommendations (see below).

Alright, it’s pretty clear there’s not much to worry about when it comes to exercising during pregnancy. However, we’ve made a case for why you shouldn’t worry about it, now let’s make a case for why you should exercise while pregnant.


Why you should:

Another quote from the 2003 recommendations:

“ In the absence of contraindications, a pregnant woman should be encouraged to engage in regular, moderate intensity physical activity to continue to derive the same associated health benefits during pregnancy as before pregnancy.”

-> To reiterate, specific contraindications are not going to be discussed here. If you think you may have a condition where you shouldn’t exercise, you should be talking with your OBGYN. Again, this is for your generally healthy, average mom-to-be.

Exercising while pregnant is good for all the same reasons it’s good when you aren’t pregnant. We can take this further though. Not only is exercising while pregnant generally healthy, but let’s talk about how it can improve your pregnancy:

1) If the average American is reading this, there’s a 66% chance the person is overweight. About a 34% chance they’re obese. Based off these percentages there are quite a bit of people who have diabetes, are at risk of diabetes, or will be at risk.

One of the biggest benefits of exercising while pregnant is reducing the risk of gestational diabetes aka getting diabetes while pregnant.

Without going into too much detail, exercise helps improve insulin sensitivity (a good thing). Obviously you always want to avoid getting diabetes but you especially want to avoid you and your baby having insulin issues.

2) Women who exercise during pregnancy have been found to have less complications later in their pregnancy. (E.g.: Exercise during pregnancy and pregnancy outcome.)

3) Women who exercise while pregnant have been found to have better experiences with labor e.g. it doesn’t take as long.

4) There doesn’t seem to be much difference, but some studies have looked at whether children of moms who exercised have any better cognitive abilities. One study found those kids were a little better at oral skills.

5) That same study found kids of exercising moms had less fat at 5 years old. There might be something to say here for all of the overweight kids nowadays: It’s not just that they play more video games, but the environment they had while in the womb might play a role as well.  If you’re mom was overweight while pregnant it appears it could increase her children’s chances of being overweight throughout life. (E.g.: Morphometric and neurodevelopmental outcome at age five years of the offspring of women who continued to exercise regularly throughout pregnancy .)

6) My pregnant client was doing an exercise the other day where she was holding 35lbs. When I handed her the weight she goes, “Crap, this is heavy.” My reply, “Just think, in a few months you’ll be carrying that around everywhere you go!”

My point here is the amount of work you’re going to be doing, just to walk around, is going to dramatically increase. Exercise gives a platform for increasing your tolerance to your body’s future changes.

If your leg muscles are already used to lifting, say 35lbs, through various exercises, that 35lbs you are going to be carrying around all day won’t feel as strenuous. Exercising can just make life easier in the latter portions of your pregnancy.

7) Lastly, the weight gain being predominantly in the front of the body predisposes pregnant women, and postpartum, to issues such as lower back and shoulder pain (the two more common ones), and even issues further down the chain like hip and knee pain. A good exercise program can help strengthen the muscles that are inevitably going to get weak during the pregnancy, help educate the mom-to-be on how to avoid inciting her pain further, etc.

Postpartum benefits

1) Either I can’t find it or it’s not out there, but there doesn’t seem to be any research specifically comparing women who exercised during their pregnancy versus those who didn’t and their rates of postpartum depression.

However, exercise has been found to help depression in non-pregnant women. Predictive factors of postpartum depression include a depressed mood pre-delivery, a negative birth experience, high BMI, excessive weight gain during pregnancy, not exercising during the postpartum phase…Exercise has been found to help all of those things. I don’t think it’s farfetched to extrapolate exercising while pregnant is probably beneficial for avoiding postpartum depression.

(For some predictive factors of postpartum depression check out: Risk factors and predictive signs of postpartum depression.)

2) Like 1),. I can’t find a study specifically looking at women who exercised and women who didn’t and their rates of postpartum weight retention, but a lot of the factors that correlate with higher levels of postpartum weight retention have been found to be bettered with exercise.

(Update: I happened to find a study that did just that. Effect of regular exercise on prevention of excessive weight gain in pregnancy: A randomised controlled trial. Those who exercised retained about a pound and those who didn’t retained about 7 pounds. Ha!)

Furthermore, if you’re already in a routine of exercising for the 9 months you have been pregnant it’s going to be a hell of a lot easier to exercise after labor. You can simply adjust your current routine now that you aren’t pregnant. Opposed to having to start a routine because you haven’t been doing anything.  Plus you’ll be in better shape in those immediate postpartum workouts.

So we basically have a slam dunk for exercising while pregnant. I mean, if I only listed the above benefits to you you’d probably ask, “What the hell drug is that and where do I get it?”

In the end worrying about whether you should exercise or not is pretty silly. All exercise is is a preconceived idea to do activity. Go to the mall for Christmas shopping, push a shopping cart around, lift some toys up to see what you think of them, push a heavier cart around, etc. Compare this with going to the gym, lift some dumbbells, walk on the treadmill for a while, push a weighted sled around, etc.

Do each of those activities for 45 minutes. What’s the difference? One is called “activity” and one is called “exercise.” Nobody is going to tell you’re not allowed to walk through the mall. Don’t think you can’t go to the gym either.

As far as intensity, how often you should be exercising, etc. All future posts. In the meantime get on a solid exercise program, hire a personal trainer, get your spouse to go on walks with you, whatever your method may be; but the first trimester is the time to get moving!

Subscribe to Blog via Email

Enter your email address to subscribe to this blog and receive notifications of new posts by email.

Posted in: Pregnancy