Welcoming a new baby into the world is one of the happiest moments for a new mother and father. After waiting nine long months, it is very exciting for new parents to finally see their new baby. However, bringing a new baby home can be very stressful, tiring, and time-consuming as well, especially to the mother. Exercise is defined as any movement that is planned and done with the purpose of maintaining or improving physical fitness (75). Being physically active reduces the risk of premature death and many chronic diseases and promotes better psychological health (23). Exercise increases neurotrophic factors, neuroplasticity, and hippocampal neurogenesis (31). Specifically, aerobic training is defined as any activity that involves large muscle groups in a continuous rhythmic way such as swimming, walking, or cycling (55).
Aerobic exercise is known to increase cardiorespiratory fitness, VO2 max, and improve heart and lung function. In general, aerobic exercise has a stronger effect on mood improvement than anaerobic exercise (26). Evenson, et.al, (29) states that postpartum physical activity can improve mood, maintain cardiorespiratory fitness, improve weight control, promote weight loss, and reduce depression and anxiety. The recommended physical activity prescription for postpartum women is at least 150 minutes of moderate intensity aerobic activity throughout the week (29). Aerobic exercise may be beneficial in improving multiple aspects of quality of life for postpartum women and thus, also improving the health of the newborn baby.
A woman’s body goes through numerous psychological and physiological changes during and after pregnancy that can put them and their baby at risk. Changes in a woman’s body during pregnancy include more than just weight gain, with changes beginning to occur after conception and affecting every organ system in her body (67). Pregnancy comes with a wide range of physical symptoms and complications such as fatigue, increased urination, nausea, tender breasts, vaginal discharge, headache, shortness of breath, insomnia, hot flashes, and Braxton hick’s contractions, just to name a few (36).
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Many of the physiological and morphological changes of pregnancy persist for 4 to 6 weeks postpartum (29). Further, 42% of postpartum women in the U.S. reported rarely or never having a good night’s sleep and 84% reported experiencing sleep problems (73). Among other changes, maternal insulin resistance begins in the second trimester and peaks in the third trimester as a result of increased secretion of diabetogenic hormones which can lead to gestational diabetes if her pancreatic function is impaired (67). Gestational Diabetes Mellitus (GDM) affects intrauterine fetal development and well-being, fetal chances of surviving pregnancy, and the later health of both mother and newborn (55).
Thousands of babies are born every day and deficits to women in the postpartum often go unnoticed and untreated. Prescribing physical activity as an intervention for complications in pregnant and postpartum women instead of pharmacological interventions could have major health and economic benefits to society. Maternal pathology is a significant concern due to its negative impact on both the mother and children (6). Post-partum depression is the most common medical complication of maternity, affecting one in ten new mothers (35). Infants born to mothers suffering from PPD grow up to be at an increased risk of developing a mood disorder themselves (18).
Barker, et.al., (6) found that maternal depression is linked to a decrease in the child’s verbal IQ and an increase in child externalizing difficulties. They also found that maternal anxiety increases child internalizing difficulties. It was found that mothers with severe postnatal depression increased their children’s risk of behavioral problems, reduced mathematics grades, and had a higher prevalence of depression (57, 73). Postpartum depression is associated with numerous maternal and infant-related consequences including poor infant-child bonding, difficulty caring for newborn, long-term behavior problems for the child, more weight retention for the mother, and future depression risk for both parents (46). An intervention to combat pregnancy and postpartum complications are of utmost importance for a mother and her new baby.
Post-partum depression (PPD) is a mental disorder that has a severe impact on post-labor mothers and their newborn babies. Negative thoughts, suicidal ideation, and anxiety are the hallmark characteristics of women suffering from postpartum depression. If symptoms appear within 4 weeks after delivery and persist for at least 2 weeks, the condition is classified as postpartum depression (1).
Symptoms of this debilitating disease include mood, sleep and appetite disturbances, weight loss, and suicidal ideation (31). Risk factors for this disease are thought to be lower socioeconomic status, obstetric complications, antenatal depressive symptoms, lower social support, and prenatal neuroticism (3). The exact pathogenesis of postnatal depression is not known but, many studies have been done that examined the serotoninergic pathway, which is known to cause general depression. Dysregulation of the immune inflammatory response and the hypothalamic-pituitary-adrenal (HPA) axis are also thought to be a cause of general depression (18).
Increasing evidence points to alterations in the two pathways of tryptophan metabolism, the kynurenine and serotonergic pathways, which are important for production in serotonin, could be the underlying pathogenesis of postnatal depression (36). Noteworthy, another study that looked at the immunological effects found that cortisol levels increased with levels of cytokines in women after childbirth which, increased their risk of developing postpartum depression (18).Exercise increases levels of serotonin, which then leads to decreased depression, according to the serotonin hypothesis (45). Psychological explanations of the positive well-being outcomes associated with exercise include: enhanced feelings of control, exercise as a distraction, improved self-concept and self-esteem, and opportunities for fun and enjoyment (51).
Several studies found that physical activity significantly decreased depressive, anxiety, or distress symptoms (4, 14, 51-54, 59, 61). It has been shown that depressed adults who took part in a fitness program displayed significantly greater improvements in depression, anxiety, and self-concept (18, 9). Treadmill exercise alleviated postpartum anxiety and increased serotonin and TPH levels in postpartum rats (27). Women who participated in exercise during pregnancy had a reduced risk of developing postnatal depression (67) however, data were collected via surveys which are not often accurate. Gobinath, et.al., (31) examined how corticosterone-induced rates show a PPD-like phenotype and found that corticosterone reduced maternal care, increased depressive-like behavior, and reduced hippocampal neurogenesis.
Further, running reduced corticosterone-induced depressive behavior and increased hippocampal neurogenesis (31). Participants in a physical activity group reported fewer depressive symptoms and had a lower score on the EPDS than a health/wellness control group (47). In contrast, Campolong, et.al., (13) did not find any differences in EPDS score of an exercised group compared to a control, which they credited to the subjects having a low risk of PPD prior to the study. Daley, et.al., (20) also found a lower EPDS score in an intervention group of women.
Evidence which had women participate in a twelve-week dance and aerobics exercise protocol found that the exercise group had significantly lower scores on the Lederman Postpartum Self-Evaluation Questionnaire, compared to the control group and thus, less depressive-like symptoms. (76). Physical activity increases endorphin levels, core body temperature, serotonergic systems, and blood flow to the brain and disrupts the HPA axis that regulates stress, all of which may be the mechanism of how exercise decreases depression. On the contrary, Daley, et.al, (21) did not find any improvements in depressive symptoms after 12 weeks of an exercise program compared to a sedentary group due to difficult to motivate the postnatal subjects to exercise.
Another study done by Norman, et.al. (26) found that exercise reduced the risk of depression by 50% after 8 weeks, however, the intervention group also participated in parenting education which could have skewed the results of this experiment because the parenting education alone also showed benefits in improvement in mood. No significant differences were found in an exercising versus a control group EPDS or Fatigue Identification Form (FIF) however, most of the subjects in the group did not keep up with the exercise program (56) therefore, these results are not conclusive. Ko, et.al. (40) found no changes in the level of depression between an exercising group and a control but, did find reduced emotional and physical fatigue in the intervention group.
Breastfeeding is a vitally important component of life after pregnancy for mother and newborn. Babies who are breastfed have a substantially greater chance better cognitive development, protection from infections and diseases, and social and physical growth (30). Evidence points to oxytocin contributing to stress reactivity, support emotional and mental well-being and promoting prosocial and bonding behavior (7), which may be important for prevention of PPD. Maternal benefits include decreased postpartum bleeding, decreased risk of breast and ovarian cancer, and earlier return to their pre-pregnancy weight (30). The longer a mother breastfeeds, the less likely they are to develop depressive symptoms and short breastfeeding duration is correlated with feelings of guilt, shame, and anxiety (9).
However, many worry that exercise can play harmful effects on the composition and volume of a woman’s breastmilk, which could play a toll on the health of the newborn baby. A few studies found that vigorous exercise did not have adverse effects on the breast milk production (61) (5). Lovelady, et.al. (49) found that average daily milk volume and breast milk composition were no different in an exercise group and levels of prolactin, cortisol, insulin or T3 were all within normal range, when compared to a sedentary group, indicating that exercise did not have a negative effect on the subjects’ breast milk. They also observed that the strenuous exercising group had a higher level of milk production and energy output in their breast milk when compared to a control (49).
No differences were found between a moderate exercising group who performed aerobic fitness for 30 minutes and sedentary group in IgA, lysozyme, or lactoferrin levels or volume of their breast milk (50). The wait-time of breastfeeding after performing exercise may play a critical impact on a nursing baby, however. Evidence recommends that a mother should wait at least 60 minutes after exercising to breastfeed by examining milk samples taken 10 and 30 minutes after an exercise session which both had reduced concentrations of IgA, IgA1, and IgA2, which are very important to a baby’s robust immune system (34).
Overall, one can conclude that physical fitness does not harm breast milk, but in fact, improves breast milk quantity and quality. Fatigue/ Sleeping Difficulties Exercise is known to improve sleeping difficulties such as sleeping quality and latency. It is often prescribed for other pathologies with sleeping problems as a symptom, such as cancer. Therefore, it is possible that aerobic activity could improve sleep in new mothers. Slow-wave sleep and stage 4 sleep increased from a physical activity regime, but the study had a very small sample size of only 9 people (11).
It was shown that aerobic exercise on a cycle ergometer increased stage 4 sleep and decreased sleep latency, while also increasing total sleep time compared to a non-exercising group (53). The authors noted that physical exercise may increase sleep onset through an arousal mechanism. However, it is important to note that this study only used male subjects so, it is not conclusive for females. In an earlier study on rats, Matsumoto, et.al. (52) found contrasting evidence that sleep latency was prolonged, indicating that the rats required more time to fall asleep following a bout of a swimming exercise. It is well known that with a new baby also comes a disturbance in a new parent’s sleep cycle. Delivery causes physical, physiological, and psychological effects on women’s sleep (63).
Lack of sleep can result in exhaustion, impatience, lower ability to concentrate, and a poorer quality of life and is associated with postpartum depression (46). Most women experience significant disturbances in sleeping as early as the first trimester (37), due to hormonal changes and newborn care responsibilities (75). Sleep is also vitally important for the consolidation of memories and brain plasticity (62). Insufficient sleep affects memory, decision-making, psychomotor skills, and mood (66). Exercise decreases sleep-deprived memory impairment in female rats (59).
The average new mother gets only 4 hours of sleep a night, wakes up more than 4 times a night, and needs 60+ minutes to fall to sleep, indicating poor sleep quality, latency, and efficiency (39). Campbell, (12) found that the average baby interruption a night was three times and that these interruptions caused feelings of emotional and physical tiredness. If a disturbance in sleep cycle persists or worsens, it may negatively influence breastfeeding and mother-infant bonding (75). It has also been discovered that lack of sleep in postpartum and development of postpartum depression may be correlated (45). Iranpour, et.al., (66) found that women suffering from poor sleep quality are three times more likely to develop depression. Aerobic gymnastic exercise was shown to decrease fatigue after only four weeks and continued to show improvements after twelve weeks compared to a sedentary group and improved sleep quality (74).
Increases in physical activity were also shown to be associated with good sleep quality and short sleep duration (73) in postpartum women. Lewis, et.al., (46) found that higher scores on the Pittsburgh Sleep Quality Index (PSQI) were correlated with higher depressive symptoms. In contrast, (47) and (9) did not find a positive correlation between exercise and quality of sleep. Weight Loss The postpartum period of a woman’s life is a very vulnerable time for weight gain and the development of obesity (28). Women, on average, gain around 30 extra pounds during pregnancy and often have a difficult time getting back to their normal weight after childbirth. Most new mothers retain weight of 10 pounds or more after pregnancy (8).
Excessive maternal weight gain (MWG) is a risk factor for hypertension, GDM, preeclampsia, cesarean delivery, macrosomia, stillbirth, and perinatal complications (62). Mothers with greater amounts of fat during pregnancy deliver greater amounts of glucose and fatty acids to the fetus, which leads to greater adiposity throughout the baby’s life (42). Weight retention puts mothers at risk for high blood pressure, diabetes, and cardiovascular disease (28). Women who lose pregnancy weight by six months postpartum have less long-term weight gain (57). Weight loss in these individuals is of utmost importance for their health, their baby’s health, and to lessen the growing increase in obesity in the U.S. Frequent bouts of aerobic exercise are the best way for postpartum women to put off the baby weight and get back to a healthier weight.
For example, Sampselle, et.al., (63) found that women with higher levels of activity retained less weight than those who were not active. A meta-analysis found that women who participated in aerobic exercise through pregnancy gained less weight than sedentary pregnancy women (41). Women in an exercise regime obtained significant decreases in weight, fat mass, and fat percentage (39). Lovelady, et.al., (48) found a reduction in percent body fat and weight in a postpartum exercising group while a sedentary group showed no improvements. Other research found that physical activity did not have any positive effects on weight loss compared to a control group but, the sample size of this study was very small (25).
A twin study done found that greater maternal weight gain (MWG) was associated with a higher birth weight within siblings and non-siblings and found a positive correlation between MWG and offspring BMI within siblings (42). Gestational Diabetes Mellitus (GDM) is triggered by metabolic and hormonal changes during pregnancy (16). GDM is associated with preeclampsia, hypertension, preterm birth, and induced and cesarean deliveries (64). These women are also more like to be overweight and develop type 1 or 2 diabetes later in life. The primary site of insulin resistance in gestational diabetes is in the skeletal muscle, which is also the location of increased uptake and glucose utilization during exercise (24).
Physical activity has been associated with a reduced risk of type 2 diabetes (24), therefore, it is plausible that it could greatly decrease the probability of pregnant or postpartum women developing gestational diabetes. A few studies found that moderate or high levels of exercise before pregnancy greatly reduced the risk of developing gestational diabetes (60, 24). It was also noted by Dempsey, et.al., (24) that the more METs of energy expended during exercise, the greater the reduction in risk of developing gestational diabetes. Compared to moderate exercise, vigorous exercise was shown to reduce both glucose and insulin levels following a bout of exercise which also reduced the risk of being diagnosed with GDM (55).
A meta-analysis found that exercise during pregnancy reduces the risk of GDM and also slightly reduces the MWG and that when begun in early pregnancy, the benefits are greater (64). However, Stafne, et.al., (69) and Callaway, et.al., (44) did not find any differentials in lower fasting insulin or insulin resistance between an intervention group who performed aerobic exercise and a control group who was sedentary and thus there was no correlation found between exercise and the prevalence of gestational diabetes. Contrary to the meta-analysis mentioned above, Streuling, et.al., (71) found inconsistent results between studies that exercise improves GDM.
Stafne, et.al., (69) noted that it may be more beneficial to women to perform regular exercise bouts before pregnancy and in early pregnancy because of the chronic changes in skeletal muscle regulation of glucose uptake are adapted, and they would be able to better handle metabolic stress. Engaging in physical activity both before and during pregnancy will likely lead to the greatest reduction in GDM risk (17).Physical activity prior to and during pregnancy may be vitally important for the baby as well. Physical activity may be advantageous on a baby’s birth weight, the timing of delivery, later disease progression, and reduce detrimental effects on premature babies (65).
Some would argue that physical activity during pregnancy can be harmful to the baby but, Hellenes, et.al., (33) did not find any effect of moderate level exercise on the cognitive or language development nor the motor skills of the offspring. It was also found by Clapp, et.al, (16) that low-high and moderate level exercising mothers had lighter and shorter offspring than women in a high-low group, however, it is important to note that genetics plays a strong role in these features as well. Regular low-to-moderate exercise reduces the risk of babies born at an extreme birth weight (59). Women exercising at low-to-moderate exercise during pregnancy were found to have lower pregnancy symptom scores and more exercise early in pregnancy was related to fewer symptoms later in pregnancy (70).
On the other hand, moderate or vigorous activity was found to be associated with a 70% decrease in large infant size for gestational age (LGA), (2). Leiferman and Evenson, (43) found that non-exercisers were more likely to give birth to a baby with a low birth weight than an exercising group. Women who exercised regularly before becoming pregnant were found to have lighter and leaner babies (15). It was observed in rats whose mothers exercised that the learning process was improved and had increased hippocampal activity in the rat offspring (22). Postpartum is a very difficult time for new mothers- they assume responsibility for caring for the baby once they arrive home from the hospital, while still trying to recover from the pain and difficulty of childbirth.
Consistent with the thesis statement, aerobic exercise appears to improve multiple aspects of quality of life for postpartum women. Exercise may improve insulin resistance, oxidative stress, decrease body fat, dyslipidemia, and decrease blood pressure (24). Hellenes, et.al. (33) found that exercise did not harm the development of the baby. Sternfeld, et.al., (69) stated from their research that exercise helps to lessen pregnancy symptoms. Leiferman and Evenson, (43) discovered that an exercising group of women was less likely to give birth to a low-birth-weight baby than a sedentary group. Also, important to note is that exercise during pregnancy may help to improve memory and hippocampal neuronal activity, as shown by (22).
Lastly, Clapp, et.al., (15) found that women who were regular exercisers before becoming pregnant were more likely to have lighter and learner babies than those who did not. Therefore, improvements via physical activity may be beneficial in improving multiple deficits in postpartum women, unlike pharmacological interventions. Health problems begin to arise in new mothers when they have difficulty losing the extra baby weight and getting back to their old weight. Aerobic exercise is the easiest and most cost-effective way for these individuals to get back in shape, while also benefiting their new baby in the long-term. Sampselle, et.al., (63), (41), (39), and (48) all concluded from their research that aerobic exercise can positively affect new mothers by reducing percent body fat, while Dewey, et.al., (25) did not find any positive correlations from their research.
Maternal weight gain (MGW), as mentioned above, can lead to adverse conditions in these individuals. Gestational Diabetes Mellitus (GDM) is a complication that can arise during or after pregnancy and puts women at risk for developing type 1 or 2 diabetes later in life. Redden, et.al., (59) and (25) both found that moderate to vigorous levels of exercise decreased the chances of developing GDM. Medek, et.al., (55) found that vigorous exercise specifically reduces glucose and insulin levels. Sanabria-Martínez, et.al., (62) and (17) discovered that the earlier physical activity is started, the less likely a woman is to develop GDM. On the contrary, (69), (44), and (71) all had inconsistent results that were not conclusive for aerobic exercise as a preventative measure for GDM.
There has been a plethora of research regarding how different forms of physical activity can elevate symptoms of depression, anxiety, body dissatisfaction, stress, and quality of life. The majority of the research favors aerobic exercise interventions as a means of treatment for postpartum depression. (14, 4, 51, 59, 61, and 54) all found a significant decrease in symptoms of postpartum depression following a controlled exercise regime. In contrast, (13, 26, 21, 40, and 56) all did not find any differentials in their studies when comparing postpartum symptomology to a control group.
Breastfeeding can be difficult for some mothers but, it is extremely beneficial to a newborn’s health. Breastfeeding mothers are also likely to develop postpartum depression if there are complications with breastfeeding. There is often concern about how exercising postpartum can affect the breast milk volume and nutrients that are crucial for a baby’s growth and development. However, (5, 49, and 63) all found positive correlations between moderate to vigorous exercise levels and breast milk quantity and quality.
Fatigue and sleeping disturbances are a very common occurrence once a new baby is brought home from the hospital. Trouble sleeping can also occur in the first, second, and third trimester of pregnancy as well as nausea, back pain, and general discomfort. These irregularities in sleep can lead to issues with concentrating, mood, memory, and can even lead to postpartum depression. Lewis, et.al., (46) found a correlation in their research that linked lack of sleep to development of postpartum depression. Vladutiu, et.al., (73) and (75) all found that aerobic exercise helped to improve sleep quality and decrease the level of fatigue in new mothers. Overall, it can be assumed from the data collected that aerobic exercise done on a chronic level before pregnancy and during, shows numerous benefits throughout pregnancy and postpartum.
A majority of these experiments examined changes in the subjects via surveys such as the Edinburgh Postnatal Depression Scale (EPDS) and the Pittsburgh Sleep Quality Index (PSQI) which is not the most accurate way to collect research data for comparison. EPDS is used more to determine risk factors for postnatal depression and thus, correlation cannot equal causation in many of these experimental results. It is also important to note that most of these experiments did not find any significant differences in the age, race, education, BMI, or income of the subjects. The majority of the exercise regimes in the experiments were twelve weeks long, suggesting that these results are valid. Taken together, these findings suggest that offering postpartum women exercise physical therapy or OBGYNs suggesting home-based exercise after childbirth could greatly improve the quality of life and decrease after-birth complications in these individuals.
