Should you exercise during pregnancy?
10 facts about resistance training during pregnancy
There are many misconceptions regarding what is considered suitable exercise for pregnant women. What forms of movement are „safe” to do during this life period and what should you avoid? According to WHO guidelines “women who, before pregnancy, habitually engaged in vigorous-intensity aerobic activity or who were physically active, can continue these activities during pregnancy and the postpartum period”. This means, that if you had been sedentary before your pregnancy, it’s probably not the right time to pick up a new gym routine, but if you had been engaging in regular physical activity before, you don’t have to – and you shouldn’t – stop exercising. However, it is still quite common for pregnant women to avoid exercising at a moderate to high intensity. In many cases most prenatal exercise programs are of low intensity, such as prenatal yoga or Pilates. Unfortunately, there’s a lack of knowledge among pregnant women what kind of physical activities they can or cannot do during pregnancy as one systemic review has pointed out. Most health care providers don’t provide “prescriptions” for suitable exercise programs and pregnant women resort to getting their information elsewhere, such as from the internet. Hopefully, if sports scientists work more closely together with medical professionals, it will help spread information and lead to the promotion of prenatal exercise among pregnant women. Most current research on the topic shows a positive correlation between exercise and pregnancy health outcomes, especially the combination of strength training, stretching, balance and aerobic exercise.
Of course, it goes without saying, in certain situations it might be advisable to avoid vigorous movement, and you should always talk to your health practitioner before engaging in exercise. Now, if your doctor has cleared you for physical activity, what are the benefits of exercise for pregnant women?
The history of exercise recommendations for pregnant women
The earliest recommendations regarding exercise for pregnant women emerged in the early 20th century and were based more on tradition than on science. Even the 1985 recommendations of the American College of Obstetrics and Gynecologists (ACOG) used animal studies to base their recommendations on. In these clinical trials, the studied species were pushed to levels of physical exhaustion which is not even close to the level of intensity of prenatal exercise. It is the result of extensive human studies and research that the current recommendations encourage physical activity at a moderate intensity for 30 minutes or longer on most if not all days of the week.[1] However, it is commonly acknowledged that pregnant women should get a green flag from their physicians before they continue or start an exercise routine, since in the case of a high-risk pregnancy, vigorous physical activity might not be advised. It is also common that fitness centers only provide prenatal classes after the first trimester since the chance of miscarriage is always higher in the early months of pregnancy. Although there is no scientific proof that physical activity could increase the risk of miscarriage, fitness professionals remain cautious due to the legal concerns if such event occurs.
Benefits of prenatal exercise
1. Improved Weight Management
A recent article in the Strength and Conditioning Journal cited a series of studies showing correlation between prenatal exercise and moderate weight gain during pregnancy. One study found that women who led an active lifestyle throughout their pregnancies gained 20% less weight than those women who stayed sedentary. These findings are important, because the higher the weight gain during pregnancy, the more likely that these women will keep the weight postpartum. Since obesity is a leading cause for non-communicative diseases, long-term weight management is key to a long and healthy life. Although some weight gain is inevitable during pregnancy, for healthy women who fall into the normal BMI range, it is between 11 and 16 kilograms, while for overweight or obese women the current recommendations are between 5-11 kilograms. This 2022 narrative review looked at several studies and concluded that a high maternal BMI could potentially put women at a greater risk of miscarriage, stillbirth, and maternal death as well. As a result, it is safe to say that exercising during pregnancy to create an optimal calorie balance and moderate maternal weight gain is beneficial.
2. Less chance of developing gestational diabetes
Gestational diabetes mellitus is a common complication during pregnancy and it affects around 10% of all pregnant women. Studies have shown that mothers with gestational diabetes are more prone to developing diabetes postpartum and their children are at higher risk of obesity. Several clinical trials have shown a positive correlation between exercise and improved insulin sensitivity. A 2022 Review in Sports Medicine compared different forms of exercise routines and their effect on fasting insulin and glucose levels, and found that a combination of resistance training and a moderate to vigorous aerobic activity yields greater results that those two alone. Therefore, a healthy pregnant woman should aim to perform both resistance training and cardiovascular activities during her pregnancy.
3. Reduced incidents of preeclampsia
Pregnancy induced hypertension is observed in around 2-8% of pregnant women, while preeclampsia affects about 1% of pregnant women.[2] The difference between hypertension and preeclampsia - in very basic terms - is that the latter also includes proteinuria and developing edemas. It is a serious condition that can lead to seizures and cerebral hemorrhage. It contributes to 16% of maternal deaths but is can also cause premature births. According to this article in the International Journal of Environmental Research and Public Health, exercise has a well-documented effect to decrease obesity and hypertension. Furthermore, physical activity can modify certain elements that potentially lead to the development of preeclampsia, such as a reduction in oxidative stress, and other hormonal responses, that contribute to maintaining or improving blood flow.
4. Better psychological well-being
One of the positive “side effects” of training during pregnancy is an improved acceptance and satisfaction with the “pregnancy body”. Women who exercise during their pregnancies tend to have better body-image than women who remain inactive. This strongly correlates with emotional well-being. Exercising is also beneficial against mood swings and depressive symptoms which can increase by 15% during pregnancy. This is likely related to the fact that exercise results in increased biosynthesis of neurotransmitters, improved body composition and being more capable to complete physical tasks.
5. Reduced lower back pain
Lumbosacral pain is one of the most common musculoskeletal issues that affects women during their pregnancy. Almost 80% of pregnant women experience pain in the lumbar region, which can be attributed to weight gain and a change of body shape. Also, hormonal secretion of relaxin can affect the spinal ligaments, making them less stable and capable to withstand the heightened physical demands, such as the shift in the center of gravity. However, strengthening the core musculature, especially the posterior muscles of the trunk (such as the latissimus dorsi and rhomboids) can alleviate maternal back pain. And although any type of exercise is beneficial during pregnancy, a well-planned prenatal strength program has unique, added benefits.
6. Improved fetal development
Not so long ago, women were advised against intense physical activity to ensure a healthy and safe delivery. However, the consensus has shifted since, and ACOG now observes that “children born to women who performed weight-bearing exercise 3–5 times per week throughout pregnancy were longer and had more lean body mass than matched controls”. Furthermore, these children showed more advanced neurodevelopment than their control group. These findings were explained by the fact that regular exercise increases blood volume, cardiac output, and placental function. The fetus thus receives an increased 24-hour nutrient delivery, which improves fetal nourishment.
7. Easier labor
Physical activity has been associated with a lower risk of premature labor, fewer incidents of C-sections and a shorter time spent in the hospital. Furthermore, high levels of resistance training have shown to reduce the time spent in active labor, as well as the incidents of acute fetal stress.
Misconceptions about prenatal exercise
8. Hyperthermia
In the early animal-studies researchers found a correlation between the warming up of the mother’s core temperature and neural tube defects of the fetus. However, these results did not reflect on the human studies, in fact, exercising up to 70% of maximum heart rate did not make a difference on the mother’s core temperature. This can be due to better heat-regulation in the form of sweating during exercise.
9. Miscarriage
As mentioned before, the biggest concern of expecting mothers when it comes to exercise is the possibility of losing their child. However, these fears remain unsupported by scientific research. On the contrary, some studies found that women who remained physically active had a lower rate of spontaneous abortion than women who were sedentary. Other studies examined women that were training at a higher level and at higher intensities, also found no evidence for miscarriage or implantation problems.
10. Joint-related injuries
One of the most valid concerns of prenatal exercise is the risk of soft-tissue injury to the joints. As a result of secretion of the hormone, relaxin, tendons and joints become more elastic, accommodating the growth of the fetus, and later, with delivery. However, it also makes these connective tissues more susceptible to strains and tears. Interestingly, scientific research didn’t find an increased number of prenatal exercise induced injuries. On the other hand, since resistance training strengthens the connective tissues, properly executed exercise could even be beneficial to reduce the risk of injuries.
Conclusions
These findings are not very recent. Most of the abovementioned studies were conducted in the 1990s and previous, more conservative recommendations of ACOG were revised. However, contrary to all the listed benefits, a cross-sectional study of 1279 patients found that more than half of the female participants stopped their usual exercise routines because of pregnancy. In most cases the obstacles to physical activity are environmental – lack of access to exercise facilities, lack of education regarding the safety of prenatal exercise, and socio-economic or individual (physical and emotional barriers). Hopefully, education and improving the accessibility of prenatal exercise programs could encourage pregnant women to engage in prenatal exercise.
There is a broad scientific consensus that obesity is one of the greatest risks for pregnancy, while almost half of the women that become pregnant are already classified as overweight or obese. [3] Pregnant women tend to have strong trust in their obstetricians and tend to listen to the advice they get from them. Therefore, it is crucial that healthcare professionals are aware of the numerous health benefits that physical activity can provide during and after pregnancy. In my opinion, prenatal exercise should be “prescribed” to patients, whenever possible. On the other hand, fitness professionals also need to be better equipped to work with prenatal clients. Luckily, there are several pre-and postnatal continuing education courses for fitness professionals but unfortunately, the standard personal training qualifications just don’t give sufficient information regarding the programming and execution of a prenatal exercise program. The way I see it, not every personal trainer needs to be an expert in pre-and postnatal training, however, it is important to be able to give evidence-based information regarding prenatal exercise, and possibly a referral to a specialist in their network.
[1] Schoenfeld, Brad MSc, CSCS. Resistance Training During Pregnancy: Safe and Effective Program Design. Strength and Conditioning Journal 33(5):p 67-75, October 2011. | DOI: 10.1519/SSC.0b013e31822ec2d8
[2] Poniedziałek-Czajkowska, E.; Mierzyński, R.; Leszczyńska-Gorzelak, B. Preeclampsia and Obesity—The Preventive Role of Exercise. Int. J. Environ. Res. Public Health 2023, 20, 1267. https://doi.org/10.3390/ijerph20021267
[3] Poniedziałek-Czajkowska, E.; Mierzyński, R.; Leszczyńska-Gorzelak, B. Preeclampsia and Obesity—The Preventive Role of Exercise. Int. J. Environ. Res. Public Health 2023, 20, 1267. https://doi.org/10.3390/ijerph20021267
