Strength training offers significant benefits for physical and mental health, but many expecting parents wonder whether lifting weights is safe during pregnancy. While there is extensive research on exercise during pregnancy, specific studies on strength training are limited. This episode examines what the evidence tells us about resistance training during pregnancy. You will learn how pregnancy-related changes can affect your strength training workouts, what precautions to take, and how to modify exercises safely. Whether you are an experienced lifter or new to resistance training, this episode will help you approach strength training during pregnancy with confidence.

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Exercise in Pregnancy

There is a separate episode that provides an overview of exercise during pregnancy. That episode covers general recommendations, safety considerations, and how pregnancy-related changes and common symptoms can affect your workouts. It lays the foundation for understanding how to approach exercise during pregnancy, so I recommend listening to it first before diving into this episode on strength training. This episode is the final installment in a series on exercise during pregnancy, following episodes on cardio and yoga.

What is Strength Training?

Strength training is a form of exercise that increases your muscle strength. When most people think of strength training, they picture lifting weights at a gym, but the category is much broader than that. Strength training includes using resistance bands, kettlebells, machines, and body-weight exercises such as push-ups, pull-ups, and squats. Even plyometrics and certain styles of yoga can fall under the umbrella of strength training. The key is that these exercises challenge your muscles against resistance, whether that resistance comes from free weights, your own body weight, elastic bands, or a machine.

Benefits of Strength Training

There is a substantial body of evidence on the benefits of strength and resistance training for both physical and mental health. Strength training positively benefits your metabolism, reduces body fat, improves physical performance, improves insulin sensitivity, reduces the risk of type 2 diabetes, and promotes bone development and density. Beyond the physical benefits, strength training can reduce symptoms of depression, boost self-esteem, and even enhance cognitive function.

Strength training becomes even more important as we age. Muscle mass decreases 3-8% every decade starting in your thirties. After age 50, muscle loss increases to 5-10% per year. This decrease in muscle is accompanied by a reduction in resting metabolic rate and increased fat accumulation. Maintaining muscle strength during pregnancy and beyond can help counteract these long-term changes.

One study specifically examined strength training during pregnancy and found that it decreased fatigue and increased both physical and mental energy. A systematic review of 61 randomized controlled trials examined the effects of different types of exercise on maternal health. The researchers found that the exercise modality that seems to induce the most favorable effect on maternal health is a combination of aerobic and resistance exercises. In other words, combining cardio and strength training appears to yield the best outcomes during pregnancy.

The Research on Strength Training During Pregnancy

Even the American College of Obstetricians and Gynecologists acknowledges that the literature on strength training during pregnancy is sparse. ACOG attributes the lack of research to resistance training not being considered a safe activity in early guidelines for exercise during pregnancy. This was due to concerns about potential injury and possible fetal heart decelerations. As a result, many early studies focused on other forms of exercise, leaving a gap in our understanding of strength training specifically.

While there is a lot of research on exercise during pregnancy, relatively few studies examine strength training in detail. One small study showed that low-to-moderate strength training is safe during pregnancy. In this study, the training included a 45-minute session of 5 exercises with two sets of 15 reps each. The exercises were all performed on machines and included leg extension, leg press, arm lat pull-down, leg curls, and a lumbar extension. The participants experienced no adverse effects.

A larger study with 160 women found that light-intensity resistance training and toning exercises performed over the second and third trimesters of pregnancy do not have a negative impact on the newborn’s size or overall health. This is important because one of the theoretical concerns about exercise during pregnancy is that it could redirect blood flow away from the baby, potentially affecting growth. This study found no evidence of concern with light-intensity resistance training.

One study found moderate to vigorous resistance exercise to be safe in pregnancy. This study used a modified version of BODYPUMP workouts, which involved high repetitions with lightweight barbells. Sessions were one hour, including warm-up and cool-down. To modify the workouts for pregnancy, squat jumps were exchanged for heel raises, squats were performed with less depth, and abdominal training was replaced with pelvic lifts and static abdominal exercises. This study demonstrates an important principle, which is that you can modify almost any exercise to make it appropriate for pregnancy.

The overall takeaway from the research is that low-to-moderate-intensity resistance training appears safe during healthy pregnancies. We need more research on higher-intensity strength training and on resistance training in the first trimester, but the available evidence is encouraging.

Physical Changes During Pregnancy That Can Impact Strength Training

Before diving into practical tips and precautions, it is helpful to understand how pregnancy changes your body in ways that directly affect strength training. Being aware of these changes helps explain why certain modifications may feel necessary as your pregnancy progresses.

Relaxin and Joint Stability

The hormone relaxin increases during pregnancy to help loosen ligaments in preparation for labor and birth. Your ligaments are the connective tissues that help keep bones, joints, and organs in place. If you stretch a ligament too far or tear it, the resulting injury is a sprain.

While relaxin’s effect on the pelvis is beneficial for birth, it affects ligaments throughout your entire body during pregnancy. This means your joints have less stability, and it is easier to overstretch your ligaments, which can cause pain or injury. When strength training, this increased joint laxity means you need to be more mindful of form and avoid movements that push your joints to their maximum range of motion. What felt stable and controlled before pregnancy may feel looser or less secure now.

Your Growing Belly and Exercise Position

Your growing belly presents several challenges for strength training. As your uterus expands, it puts more pressure on your vena cava, the main vein that carries deoxygenated blood from the lower half of your body back to your heart. If there is significant pressure on this vein, it could decrease blood flow, which could ultimately reduce oxygen delivery to you and your baby. This concern has been raised particularly regarding sleeping on your back and exercising in a supine position.

A systematic review examined whether prenatal supine exercise is associated with adverse outcomes. The researchers found that although many countries caution against supine exercise after 16 weeks of pregnancy, these recommendations are primarily based on expert opinion rather than explicit scientific evidence. Overall, the researchers concluded that supine exercise is not associated with adverse pregnancy outcomes. However, there is insufficient evidence to definitively determine whether exercise in the supine position is safe or should be avoided during pregnancy.

It is important to recognize that there is a difference between spending several hours lying on your back and lying on your back for a few minutes to complete an exercise. You can also modify some exercises to use an incline rather than lying completely flat on your back. If you are planning several exercises or repetitions in a supine position, you can mix up your routine to alternate positions, so you have breaks between sets that require you to be on your back. The most important factor is how you feel. If you feel lightheaded, nauseated, short of breath, or uncomfortable while on your back, that is a clear signal to change position.

Your growing belly may also limit which machines or positions you can comfortably use. It will become uncomfortable to lie on your belly or have your belly resting against a machine. If you are doing pushups, you will not want to start lying on your belly. Plus, you may not be able to lower all the way to the ground without putting pressure on your abdomen. If you are lifting weights in front of you, be careful when holding weight further away from your body, as this increases your risk for injury. Your growing belly can also throw off your center of gravity, affecting your balance during certain exercises.

The Valsalva Maneuver

In the past, doctors thought that the Valsalva maneuver during pregnancy could reduce blood and oxygen flow to your baby. This was one of the reasons some medical providers advised against strength training during pregnancy. The Valsalva maneuver is a breathing technique commonly used during heavy lifting. Generally, you take a deep breath into your belly before the repetition. Then, during the most strenuous part of the rep, you exhale with your glottis closed so that no air escapes. Your glottis is a structure in your windpipe that controls the flow of air in and out. After the most challenging part of the lift, you exhale fully. This breathing technique creates pressure in your abdominal and thoracic cavities, which helps stabilize your spine and reduce the load on your back.

The concern was that this increased intra-abdominal pressure could affect blood flow to the placenta. However, more recent research using 3-D Doppler ultrasound shows that placental blood flow does not decrease during the Valsalva maneuver. This is reassuring news for those who use this technique as part of their lifting practice. That said, if you are new to strength training, you do not need to incorporate the Valsalva maneuver. Focus on maintaining steady breathing throughout your lifts.

Core and Pelvic Floor Considerations

When strength training during pregnancy, it is important to pay attention to your core and pelvic floor. Your core is not just your abdominal muscles. It includes your diaphragm, back muscles, and pelvic floor. These muscles work together to manage pressure inside your body and support movement.

As your pregnancy progresses and your belly grows, your abdominal muscles stretch to accommodate your growing uterus. In some cases, the two sides of the rectus abdominis muscle may separate slightly along the midline, a condition called diastasis recti. This is a normal adaptation to pregnancy, but it does change how your core functions.

When strength training, avoid exercises that cause your belly to dome or bulge outward, as this can place additional stress on the abdominal wall. Instead of traditional crunches or sit-ups, focus on exercises that maintain a neutral spine and engage your deep core muscles without creating excessive intra-abdominal pressure. Modified planks, standing exercises, and movements that incorporate breathing can all support core strength without exacerbating abdominal separation.

Your pelvic floor also deserves attention during strength training. The pelvic floor muscles support your bladder, uterus, and bowel. During pregnancy, these muscles are under increased strain due to the weight of your growing baby and hormonal changes. Heavy lifting or exercises that create a lot of downward pressure can stress the pelvic floor further. Signs that you may be placing too much strain on your pelvic floor include leaking urine during exercise, a feeling of heaviness or pressure in your pelvis, or pain during or after certain movements. If you experience any of these symptoms, it is worth consulting with a pelvic floor physical therapist who can assess your specific needs and provide targeted exercises.

Lifting Heavy Objects in Daily Life

ACOG addresses lifting in relation to occupational considerations if you work in a job that requires you to lift items regularly. ACOG states that lifting, in particular, poses a risk of musculoskeletal injury and low back pain during pregnancy. The National Institute of Occupational Safety and Health has developed recommendations specifically for pregnant workers. These limits vary based on where you are in your pregnancy, the height of the lift, the distance from your body the item is held, and how frequently you are lifting. The weight limits are relatively low, especially for lifting from below your waist.

Unfortunately, it does not work well to extrapolate these workplace guidelines directly to weight lifting or strength training. Lifting a heavy box that you have to hold away from your body is very different from lifting a dumbbell, kettlebell, or barbell in a controlled gym environment. Workplace lifting often involves awkward positions, repetitive strain, and unpredictable movements, whereas strength training typically involves proper form, controlled movements, and gradual progression.

That said, the principles behind workplace lifting safety still apply. Keep the weight close to your body, avoid twisting, use your legs rather than your back, and listen to your body. If a weight feels too heavy or you feel strain in your back or pelvis, reduce the load.

Experience Level Matters

There is a significant difference between someone who has been strength training for years and someone just starting to incorporate weights into their exercise routine. Your experience and comfort level with strength training will affect how you approach these exercises during your pregnancy.

If you have been lifting weights regularly before pregnancy, you can generally continue with modifications. Your body is already adapted to the movements, you understand proper form, and you have a baseline sense of what feels right for your body. You may need to reduce weight, adjust your range of motion, or modify certain exercises as your pregnancy progresses, but the foundation is there.

If you are new to strength training, pregnancy is not the time to jump into an advanced program. That does not mean you should avoid strength training altogether. It means you should start conservatively, focus on learning proper technique, and build gradually. Working with a knowledgeable instructor or trainer, especially one with experience training pregnant clients, can be invaluable.

Regardless of your experience level, it is essential to use weights, bands, or machines correctly to prevent injury. There are many resources available to help you learn proper lifting techniques. The best resource is working with someone in person who can observe your form and provide real-time feedback. This could be a personal trainer, an instructor at your gym, or a friend who is knowledgeable about strength training. Many gyms offer group classes with instructors available to assist with technique, which tend to be more cost-effective than one-on-one personal training.

Warning Signs to Stop Exercising

Most of the warning signs that indicate you should stop exercising are straightforward. The list from ACOG includes regular, painful contractions of the uterus, bleeding, fluid gushing or leaking from the vagina, feeling dizzy or faint, shortness of breath before starting exercise, chest pain, headache, muscle weakness, calf pain, or swelling.

Paying attention to your body and how you feel is the key to keeping your workouts within safe limits. If you feel excessively fatigued, overly winded, or uncomfortable, that is a signal to slow down or stop. You may also need to modify your training as your pregnancy progresses. What felt manageable in your first trimester may feel too intense in your third trimester, and that is completely normal. Listen to your body, and if you feel like you may be overdoing it, you probably are.

Practical Tips for Strength Training During Pregnancy

Now that you understand the research and the physical changes that can affect strength training, here are some practical tips to help you train safely and effectively during pregnancy.

Focus on Proper Form

Proper technique is always important in strength training, but it becomes even more critical during pregnancy when your joints are less stable and your center of gravity is shifting. Good form maximizes the benefits for the muscles you are working and helps prevent injuries. If you are not confident in your ability to perform an exercise correctly, do not do it. Or seek instruction from someone knowledgeable before attempting it.

Modify Exercises as Needed

You can modify almost any exercise to make it work for your changing body. Here are some practical modifications to consider. Switch free weights for resistance bands if holding weights feels uncomfortable or unstable. Decrease the weight and increase repetitions. This allows you to continue building strength without placing excessive load on your joints.

Adjust your range of motion. You do not need to go through a full range of motion if it feels uncomfortable. For example, you can perform squats to a shallower depth as your belly grows. Use machines instead of free weights if you feel less stable. Machines provide more support and control.

Modify pushups by performing them on an incline. You can do this by placing your hands on a bench or wall, rather than on the floor. This reduces pressure on your belly and makes the exercise more manageable as your pregnancy progresses. Lastly, skip exercises that involve lying on your belly or that require you to hold your breath for extended periods.

Embrace Squats

Squats are a fantastic exercise during pregnancy. They strengthen your legs, glutes, and core, all of which support the physical demands of pregnancy and labor. The more squats you do during pregnancy, the more comfortable you will be in a squat position during labor, and the longer you will be able to maintain that position. There is evidence that being in an upright position, especially in a squat, is beneficial during labor and may even shorten labor. Squats can be performed with body weight alone, or you can add resistance with dumbbells, a barbell, or resistance bands.

Progress Gradually and Listen to Your Body

If you are new to strength training, start with light weights or body-weight exercises and build gradually. If you were already strength training before pregnancy, you may need to reduce your weights as your pregnancy progresses. This is not a step backward. Your body is doing an enormous amount of work growing a baby. Adjusting your training to match your body’s current capacity is smart and sustainable. Some days you will feel strong, and other days you may feel more fatigued or uncomfortable. That is normal. On days when you feel good, you can push a bit more. On days when you feel tired or off, scale back. Consistency over time matters more than any single workout.

Consider Your Recovery

Strength training breaks down muscle fibers, and your body rebuilds them stronger during rest. Adequate recovery is essential, especially during pregnancy, when your body is already working hard to support your growing baby. Make sure you are allowing enough time between strength training sessions for your muscles to recover. For most people, this means strength training two to four times per week with rest days in between.

Hydration and Nutrition

As with any exercise during pregnancy, hydration and nutrition are critical. Drink plenty of water before, during, and after your workouts. If you are strength training regularly, you may need additional calories to support both your activity and your pregnancy. Pay attention to your hunger cues and make sure you are eating enough to fuel your workouts.

Progression Through Pregnancy

Your strength training routine will likely need to change as your pregnancy progresses. In the first trimester, many women can continue their pre-pregnancy routine with minimal modifications. Although fatigue may require you to reduce volume or intensity. In the second trimester, as your belly grows and your center of gravity shifts. That means you may need to modify exercises that involve lying on your back, balance challenges, or deep bending. In the third trimester, you may find that you need to reduce weight further, focus more on body-weight exercises, and prioritize movements that feel comfortable and sustainable. There is no single right way to progress through pregnancy. The key is to stay attuned to your body and adjust as needed.

Talk to Your Doctor or Midwife

You should discuss your exercise and activity with your doctor or midwife. Plus, take into account your experience level and the specifics of your pregnancy. If your care provider has reservations about strength training exercises you feel comfortable doing, take the time to talk through their concerns and ask for clarification. Understanding the reasoning behind their guidance can help you make informed decisions.

If you are new to strength training, working with an expert who can assist you with proper techniques is invaluable. Many personal trainers and instructors have experience working with pregnant clients and can help you design a safe and effective program. Whether you are an experienced lifter or just starting out, you can modify almost any strength training activity to feel empowered to train safely during pregnancy.

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