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Exercising Through the First Trimester

Exercising Through the First Trimester

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I am embarking on a mini blog post series to break down the pregnancy trimesters and educate clients on the important changes that occur with each, specifically when it comes to exercise. In this first blog post, I am going to cover the first trimester and provide some tips and things to avoid if you are in your first trimester of pregnancy and are wanting to embark on this exercise journey with me. 

What is the First Trimester?

The first trimester of pregnancy is marked from 0-12 weeks. This time is different for every expecting mother. Some women may feel lethargic and experience morning and evening sickness while others feel relatively normal. Some women might be ready to continue with their normal training routines while others may not. However, it is important to continue with exercise during this time as exercise can help to assuage some of the common ailments that come along with the first trimester. 

Physiological Changes

During the first trimester, women experience many physiological changes. The pituitary gland is working overtime to generate an increase in certain hormones like hCG, progesterone, estrogen, and relaxin. (Fun fact: the pituitary gland, a gland that is vital with hormone secretion, increases 2-3 times in size during the 40 weeks of pregnancy!). That is a lot of hormones causing many different changes in the body. hCG (human chorionic gonadotropin) is released right at conception and is thought to cause nausea, vomiting, and fatigue during the first trimester. Progesterone is another hormone that increases during pregnancy and has many different effects on the body. Things like heartburn, acid reflux, bloating, gas, and constipation are results of an increase in progesterone in the body. So, when it comes to exercise during this first trimester, be cognizant of these side effects and take plenty of rest time and frequent water breaks. 

Relaxin is another hormone that is released during pregnancy and “relaxes” joints, ligaments, tendons, and muscles to help the body get ready for childbirth. This can often cause instability in the joints, so certain exercises should be avoided. Exercises like kickboxing, quick lateral movements (like in tennis), and certain held yoga poses for too long putting strain on the shoulder and knee should be avoided.

Additionally, relaxin causes blood vessels to expand. However, pregnant women’s blood levels are slow to rise to fill the larger sized blood vessels. A condition called “under-fill” occurs because the same amount of blood is trying to fill these larger sized vessels, causing nausea, dizziness, or lightheadedness. To combat this issue, the body will increase its blood volume 30-50% by the end of the first trimester. Yet, this brings about a new issue of edema and swelling. Because the body needs to make room for the new blood, water is retained to later be converted to blood plasma. Thus, when women feel bloated during the first trimester, they might be experiencing this. If feelings of dizziness or nausea begin to arise while exercising, be sure to take a break or stop to let these feelings subside. 

Although it is evident the body is going through a multitude of changes during the early stages of pregnancy, it is important to continue to work out to help assuage some of these adverse effects. 

Goals of Exercise During the First Trimester

Core Strengthening 

One of the primary exercise goals during the first trimester is to build strength in the core. The core can be thought of as a box made up of the diaphragm (top of the box), the abdominals (front wall of the box), the lower back and hip muscles (back wall of the box) and the pelvic floor (bottom of the box). Having a strong core will help with carrying the baby as well as assist in making the actual process of delivery a little easier. The pelvic floor is a group of muscles that give support to the bladder, uterus, and rectum. Having a strong pelvic floor will not only help with pushing during delivery but will also help with bladder control after birth. Kegel exercises should be performed often during the first trimester to strengthen the pelvic floor. Kegels (a pelvic floor strengthening exercise) help to strengthen and support the bladder, uterus, and bowels. A kegel is performed by contacting the pelvic muscles slowly for a count of three seconds, then releasing for a count of three seconds. 

Furthermore, having strong abdominals is important to help support the mother’s lower back while carrying the baby. The transverse abdominals are especially important to target while training because they directly help with posture. 

Lower Body Strengthening 

Having strong legs is vital when carrying the extra weight of the baby while the baby is developing. Strengthening the lower body can also help control swelling and varicose veins. Strong glutes and quads as well as hamstrings will also aid in the ease of the birthing process. Exercises like squats, lunges, and inner and outer thigh exercises should be implemented early on in an exercise program. 

Key Takeaways

As you can see, there are a lot of physiological changes happening in the body during the first trimester of pregnancy. It’s important to be mindful of how you’re feeling and realize that some days are going to be better than others in regards to exercise. (And that’s okay!) Your body is going through a lot of change, so it is okay to give yourself some grace. Yet, it is important to establish good exercise habits from the start and work on strengthening the core, pelvic floor, and to be mindful of proper posture early on in order to make your pregnancy and delivery experience the best it can be. If you would like to learn more about the specific exercises we recommend during the first trimester, please reach out and let’s work together!

Yours in Wellness,



Oh Baby! Fitness Prenatal and Postpartum Training