The Effect of Swimming During Pregnancy on Fetal Growth

Woman floating in the water
October 22nd, 2018 0 Comments

Hunter Bennett

When it comes to exercise during pregnancy, the health and fitness industry is rife with differing opinions.

On one side of the equation you have a group of people that suggest that you should simply continue doing everything you did prior to becoming pregnant – that in the terms of exercise, you essentially have free reign to do whatever you want.

After all, the body is a resilient thing, right?

On the other hand, you have a group of people who firmly believe that you should completely stop doing any form of exercise during the entire pregnancy period. These individuals tend to suggest that you should allow the body time to adapt to the changes that occur in a completely sedentary manner.

Interestingly, like most things within the health and fitness industry, the true answer actually fits somewhere between these two extremes.

You see, there are several unique benefits that are obtained when you exercise throughout the pregnancy period. However, you certainly shouldn’t do exactly what you were before, because there are some modalities of exercise that can place your unborn child at more risk than others.

Which is why swimming offers such an excellent option.

Purchase Forever Fit Mama Prenatal/Postnatal Vitamins

Forever Fit Mama Subscription Box

Swimming During Pregnancy

Maintaining a somewhat normal exercise routine during your pregnancy can lower the risk of any birth complications occurring, improve your cardiovascular and metabolic health, and stave off the development of any gestational diseases.

Assuming that you have a completely uncomplicated pregnancy, the guidelines suggest that you should perform around 30 minutes of moderate intensity aerobic activity on most (if not all) days of the week. In conjunction with this, there is recent evidence to suggest that you should also perform 2-3 days of weight training per week.

However, there are a few key caveats here (Hinman, 2015):

  • You certainly want to avoid lying on the ground in the supine position after the first trimester
  • Exercise that has a risk of falling is a no go
  • High impact exercises that may increase the risk of joint damage are obviously not recommended

So, taking a bit of a look at these contraindications, it should quickly become apparent as to why swimming is such a good modality of exercise – it’s low impact, doesn’t require any real musculoskeletal loading, and is performed in the prone position.

Moreover, it offers an abundance of benefit.

Related Article: Baby On Board? – Aerobic Exercise During Pregnancy

What are the Benefits of Swimming During Pregnancy?

In a general sense, the adoption of some form of aerobic exercise (such as swimming, for example…) during pregnancy has been shown to cause rather large improvements in both cardiovascular metabolic health.

In this manner, it has been shown to lower blood sugar levels and improve the body’s sensitivity to insulin, therefore significantly reducing the risk of developing gestational diabetes (Ruchat, 2013). Importantly, this often coincides with improved blood pressure control, and a reduced risk of gestational hypertension (Martin, 2010).

Building on these positive effects a little further, this type of activity can also improve mood and increase energy levels (Poudevigne, 2005), while simultaneously reducing the risk of developing depression and anxiety (Daley, 2015).

Now, while the impact of this type of exercise on the mother is quite profound, there also some interesting research suggesting that swimming may have further benefits for the fetus.

A recent study comprised of 1854 pregnant women and the ensuing births was performed within the US. This study tracked these women throughout the duration of their pregnancy to gain insight into their daily activity levels, in which swimming was encouraged.

Incredibly, those women who swam for up to an hour per week saw an average increase in fetal birth weight of 24 grams compared to those who participated in any other form of physical activity (such as walking or cycling)

And those women who swam for more than an hour per week?

An increase of 108 grams!

While this may not sound like a huge amount, in the grand scheme of things it is quite a significant increase. Moreover, it suggests that swimming may facilitate fetal growth and ensure normal fetal development at the time of pregnancy, thus reducing the preterm delivery and a host of other congenital abnormalities (Wright, 2011).

How to Stay Safe Swimming While Pregnant?

For the most part, swimming is an extremely safe activity during pregnancy. There is almost zero risk of musculoskeletal or joint injury, it is low impact, and can be easily tailored to the individual’s fitness level.

However, there are some key considerations that need to be made:

  • Stick with high-quality swimming pools that you know use clean water.
  • Use strokes that allow you to breathe easily. The oxygen restriction that occurs when holding your breath has the potential to put both you and your child at risk.
  • Don’t train until exhaustion. While working into more vigorous exercise intensities will not harm your baby, working to complete and utter exhaustion is not recommended as it places the body under undue and completely unnecessary stress.
  • Step into the pool rather than dive in. Rapid pressure changes have been hypothesized to cause some issues with blood flow to the fetus. While there is minimal evidence to substantiate this on a such a small scale, why risk it?

By adhering to these four simple guidelines, you can get all the benefits from swimming in a safe and effective manner!

Swimming Workouts for Pregnancy

Taking all of this into consideration, we have also put together some simple swimming workouts that suit any fitness level. This means that you can start at any time, and progress as you see fit!

Beginner Swimming Workout

If you only swim once in a blue moon (or even less than that, for that matter), then no need to worry because we have got you covered. The following workout is perfect for the beginner swimmer, where it uses moderate intensities and simple strokes to ensure a safe and effective session!

It also exposes you to a number of different strokes, meaning that A) you won’t get bored, and B) that you will find out what strokes you prefer to perform, which is important when it comes to our intermediate and advanced swimming workouts.

  1. Alternate between one lap of breaststroke and then one lap of freestyle for a total of 10 minutes, all performed at a moderate intensity. By the end of the 10 minutes, you should be breathing a little heavier than normal but should still be able to maintain a conversation if required. Proceed to rest for 1-2 minutes.
  2. Swim backstroke for 10 total minutes at a relatively light intensity. This should be a gentle and comfortable pace. Proceed to rest for 1-2 minutes.
  3. Alternate between one length of freestyle and one length of backstroke for 10 total minutes. The length of freestyle should be performed at a relatively rapid pace, while the length of backstroke should be performed in a slow and controlled manner, in which it almost acts as a brief recovery.

Done in 30 minutes!

Related Article: Resistance Training during Pregnancy

Intermediate Swimming Workout

Once you feel relatively comfortable in the pool, its time to up the intensity and duration just a little bit. For this workout, you should have some strokes that you prefer more than others, that you can use for the slightly more ‘interval’ part of the session.

  1. Start by swimming laps of freestyle at a light intensity for 8 minutes. This should be performed at a fairly light exercise intensity and will serve as a warmup of sorts.
  2. Choose your favorite stroke and alternate between one lap at 75% of your maximum speed and one slow recovery lap for a total of 15 minutes. Proceed to rest for 1-2 minutes at the end of this interval component.
  3. Finish by swimming backstroke for 10 total minutes at a relatively light intensity. This should be a gentle and comfortable pace.

Advanced Swimming Workout

Our final swimming workout is for those who have a good foundation of fitness and are starting to really feel comfortable in the pool. This integrates some slightly longer intervals into the session, with slightly smaller recovery periods.

  1. Swim any stroke for 5 minutes at a light intensity as a warmup.
  2. Perform 2 whole laps of freestyle at around 80% of your maximum swim speed, and then rest for 20 seconds. Repeat this process 6 times, and then rest for 1-2 minutes.
  3. Perform 4 whole laps of whatever swim stroke you want at around 75% of your maximum swim speed, and then rest for 30 seconds. Repeat this process 5 times, and then rest for 1-2 minutes.
  4. Finish by swimming breaststroke for 10 total minutes at a relatively light intensity. This should be a gentle and comfortable pace.

Swimming Tip Per Trimester

While swimming is hands down one of the safest modalities of exercise that you can perform when pregnant, there are a few very small things that you need to consider during each trimester.

First Trimester

During this time you want to avoid any rapid position changes and try to limit the amount of time you spend at a vigorous exercise intensity.

You also want to ensure that you are staying hydrated and keeping a bit of an eye on your body temperature. If at any time you feel excessively hot, or perceive any sensation of dizziness, get out and have a quick break!

3 session of 20-30 minutes per week should do the trick during this period.

Second Trimester

At this point in time, you should be getting a bit of a baby bump. Contrary to popular belief, exercise actually gets safer from this point onwards, so feel free to integrate some slightly more Bird Dog Exerciseintensive swimming into your routine here.

Moreover, from here onwards your joints are going to become increasingly lax in preparation for childbirth. This means you should avoid any stretching as part of your warmup, as it will actually cause joint irritation!

3-5 session of approximately 30 minutes per week is fine during this trimester.

Third Trimester

By this point in time, you are going to be noticeably pregnant. In this situation, lower back discomfort is going to be much more likely. As a result, it is integral that you stick to those swim strokes that make you most comfortable. Anything that causes lower back pain should be avoided entirely.

During this stage, you should still be able to swim 3-5 times per week, for around 30 minutes per session. However, you want to make sure that you are well hydrated throughout and take rest periods as you need them!

Take Home Message

Swimming is one of the most bang for your buck forms of exercise that you can perform during pregnancy. Not only is it incredibly safe, but it has also been shown to cause large improvements in cardiovascular, metabolic, and mental health, and even positively impact fetal growth and development.

With this in mind, we have put together some great swimming workouts that you can implement during your pregnancy – so give them a try and let us know how they go!



Hinman, Sally K., et al. “Exercise in pregnancy: a clinical review.” Sports health 7.6 (2015): 527-531.

Ruchat, Stephanie‐May, and Michelle F. Mottola. “The important role of physical activity in the prevention and management of gestational diabetes mellitus.”.  Diabetes/metabolism research and reviews 29.5 (2013): 334-346.

Martin, Chantel L., and Larissa R. Brunner Huber. “Physical activity and hypertensive complications during pregnancy: findings from 2004 to 2006 North Carolina Pregnancy Risk Assessment Monitoring System.”.  Birth 37.3 (2010): 202-210.

Poudevigne, Melanie S., and Patrick J. O’connor. “Physical activity and mood during pregnancy.” Medicine & Science in Sports & Exercise 37.8 (2005): 1374-1380.

Daley, A. J., et al. “The effectiveness of exercise for the prevention and treatment of antenatal depression: systematic review with meta‐analysis.” BJOG: An International Journal of Obstetrics & Gynaecology 122.1 (2015): 57-62.

Wright, J. Michael, et al. “The effect of swimming during pregnancy on fetal growth.” Water Quality, Exposure and Health 3.3-4 (2011): 217-223.

Pregnancy and Exercise
TAGGED : , , , , ,

Leave a Reply

Your email address will not be published.

Virginia Davies, CEO

“We the people” must come together and make some real change. Read this message from our CEO and social entrepreneur, Virginia Davies.