Physical exercise during pregnancy--physiological considerations and recommendations

Heat production during exercise in pregnancy: discerning the contribution of total body weight

Studies have reported enhanced thermoregulatory function as pregnancy progresses; however, it is unclear if differences in thermoregulation are attributed to weight gain or other physiological changes. This study aimed to determine if total body weight will influence thermoregulation (heat production (Hprod)), heart rate, and perceptual measurements in response to weight-bearing exercise during early to late pregnancy. A cross-sectional design of healthy pregnant women at different pregnancy time points (early, T1; middle, T2; late, T3) performed a 7-stage weight-bearing incremental exercise protocol. Measurements of Hprod, HR, and RPE were examined. Two experimental groups were studied: (1) weight matched and (2) non-weight matched, in T1, T2, and T3. During exercise, equivalent Hprod at T1 (326 ± 88 kJ), T2 (330 ± 43 kJ), and T3 (352 ± 52 kJ) (p = 0.504); HR (p = 0.830); and RPE (p = 0.195) were observed in the WM group at each time point. In the NWM group, Hprod (from stages 1-6 of the exercise) increased across pregnancy time points, T1 (291 ± 76 kJ) to T2 (347 ± 41 kJ) and T3 (385 ± 47 kJ) (p < 0.001). HR increased from T1 to T3 in the warm-up to stage 6 (p = 0.009). RPE did not change as pregnancy time point progressed (p = 0.309). Total body weight, irrespective of pregnancy time point, modulates Hprod and HR during exercise. Therefore, accounting for total body weight is crucial when comparing thermoregulatory function during exercise across pregnancy.

A narrative review of exercise dose during pregnancy

The current recommendations for prenatal exercise dose align with those from the American College of Sports Medicine; 150 min of moderate intensity every week of pregnancy. However, recent works suggest there may be a dose-dependent beneficial effect for mother and offspring; maternal and offspring health outcomes respond differently to low, medium, and high doses of prenatal exercise. It is, therefore, our aim to summarize the published evidence (years 1950-2023) for five metrics of prenatal exercise training commonly reported, that is, "FITT-V": Frequency (number of sessions), Intensity (metabolic equivalents "METs"), Time (duration of sessions), Type (exercise mode), Volume (exercise MET*mins). The target audience includes clinicians and health care professionals, as well as exercise professionals and physiologists. Data suggest that moderate exercise frequency (3-4 times weekly) appears safe and efficacious for mother and offspring, while there is contradictory evidence for the safety and further benefit of increased frequency beyond 5 sessions per week. Moderate (3-6 METs) and vigorous (>6 METs) intensity prenatal exercise have been shown to promote maternal and offspring health, while little research has been performed on low-intensity (<3 METs) exercise. Exercise sessions lasting less than 1 hr are safe for mother and fetus, while longer-duration exercise should be carefully considered and monitored. Taken together, aerobic, resistance, or a combination of exercise types is well tolerated at medium-to-high volumes and offers a variety of type-specific benefits. Still, research is needed to define (1) the "minimum" effective dose of exercise for mother and offspring health, as well as (2) the maximum tolerable dose from which more benefits may be seen. Additionally, there is a lack of randomized controlled trials addressing exercise doses during the three trimesters of pregnancy. Further, the protocols adopted in research studies should be more standardized and tested for efficacy in different populations of gravid women.

Disinfection byproducts in chlorinated or brominated swimming pools and spas: Role of brominated DBPs and association with mutagenicity

Although the health benefits of swimming are well-documented, health effects such as asthma and bladder cancer are linked to disinfection by-products (DBPs) in pool water. DBPs are formed from the reaction of disinfectants such as chlorine (Cl) or bromine (Br) with organics in the water. Our previous study (Daiber et al., Environ. Sci. Technol. 50, 6652; 2016) found correlations between the concentrations of classes of DBPs and the mutagenic potencies of waters from chlorinated or brominated swimming pools and spas. We extended this study by identifying significantly different concentrations of 21 individual DBPs in brominated or chlorinated pool and spa waters as well as identifying which DBPs and additional DBP classes were most associated with the mutagenicity of these waters. Using data from our previous study, we found that among 21 DBPs analyzed in 21 pool and spa waters, the concentration of bromoacetic acid was significantly higher in Br-waters versus Cl-waters, whereas the concentration of trichloroacetic acid was significantly higher in Cl-waters. Five Br-DBPs (tribromomethane, dibromochloroacetic acid, dibromoacetonitrile, bromoacetic acid, and tribromoacetic acid) had significantly higher concentrations in Br-spa versus Cl-spa waters. Cl-pools had significantly higher concentrations of Cl-DBPs (trichloroacetaldehyde, trichloromethane, dichloroacetic acid, and chloroacetic acid), whereas Br-pools had significantly higher concentrations of Br-DBPs (tribromomethane, dibromoacetic acid, dibromoacetonitrile, and tribromoacetic acid). The concentrations of the sum of all 4 trihalomethanes, all 11 Br-DBPs, and all 5 nitrogen-containing DBPs were each significantly higher in brominated than in chlorinated pools and spas. The 8 Br-DBPs were the only DBPs whose individual concentrations were significantly correlated with the mutagenic potencies of the pool and spa waters. These results, along with those from our earlier study, highlight the importance of Br-DBPs in the mutagenicity of these recreational waters.

Heat loss responses at rest and during exercise in pregnancy: A scoping review

BACKGROUND

The teratogenic risk associated with maternal hyperthermia (i.e., core temperature ≥39.0 °C) has been a crucial motive in understanding thermoregulatory responses in pregnancy. To date, a substantial number of studies have focused on core temperature responses in a wide range of exercise intensities, duration, and ambient temperatures. Fortunately, none have reported core temperatures exceeding 39.0 °C. Nonetheless, there are limited studies that have provided substantial insight into both dry and evaporative heat loss mechanisms involved in facilitating the maintenance of core temperature (≥39.0 °C) during heat stress in pregnant women. The purpose of this scoping review was to summarize the available literature that has assessed heat loss responses in studies of human pregnancy.

METHODS

A search strategy was developed combining the terms pregnancy, thermoregulation, and adaptation. A systematic search was performed in the following databases: PubMed, Embase, Scopus, and ProQuest. Studies eligible for inclusion included pregnant women between the ages of 18-40 years old, and at least one measurement of the following: sweating, blood flow, skin temperature, and behavioural responses. Retrieved data were categorized as evaporative (sweating), dry or behavioural heat loss responses and summarized narratively.

RESULTS

Thirty-three studies were included in this review (twenty-nine measured physiological responses and four measured behavioural responses). Studies suggest that during exercise, evaporative (sweating) and dry (skin blood flow and temperature) heat loss responses increase from early to late pregnancy in addition to greater cardiac output, blood volume and reduced vascular resistance. Behavioural practices related to heat loss responses are also influenced by cultural/religious expectations, personal preferences and sociodemographics.

CONCLUSION

The findings from this review suggest that pregnancy modifies evaporative (sweating), dry and behavioural heat loss. However, future studies have an opportunity to compare heat loss measurements accounting for gestational weight gain and thermal sensation/comfort scale to associate physiological responses with perceptual responses across pregnancy.

Common musculoskeletal impairments in postpartum runners: an international Delphi study

Background

Postpartum runners report musculoskeletal pain with running. Because of inadequate research, little is known about the origin and pain-related classification. Through expert consensus, this study is the first attempt to understand the musculoskeletal impairments that these runners present with. The objective of this survey was to gather expert consensus on characteristics of reported impairments in postpartum runners that have musculoskeletal pain.

Methods

A web-based Delphi survey was conducted and was composed of five categories: strength, range of motion, alignment and flexibility impairments, as well as risk factors for pain in postpartum runners.

Results

A total of 117 experts were invited. Forty-five experts completed round I and forty-one completed rounds II and III. The strength impairments that reached consensus were abdominal, hip and pelvic floor muscle weakness. The range of motion impairments that reached consensus were hip extension restriction, anterior pelvic tilt and general hypermobility. The alignment impairments that reached consensus were a Trendelenburg sign, dynamic knee valgus, lumbar lordosis, over-pronation and thoracic kyphosis. The flexibility impairments that reached consensus were abdominal wall laxity, and tightness in hip flexors, lumbar extensors, iliotibial band and hamstrings. The risk factors for pain in postpartum runners were muscular imbalance, poor lumbopelvic control, too much too soon, life stressors, pain during pregnancy and pelvic floor trauma.

Conclusion

This study presents a framework for clinicians to understand pain in postpartum runners and that can be investigated in future cohort studies.

Level of evidence

5.

Training Characteristics During Pregnancy and Postpartum in the World's Most Successful Cross Country Skier

This case-study investigated the training characteristics, physiological capacity, and body composition of the world's most successful cross country skier during the 40-week pregnancy, and the 61-week postpartum. Training data was systemized by training form (endurance, strength, and speed), intensity [low- (LIT), moderate- (MIT), and high-intensity training (HIT)], and mode (running, cycling, and skiing/roller skiing). The training volume [mean ± standard deviation (median)] during pregnancy was 12.9 ± 7.3(10.0) h/week in the first- (weeks 1-12), 18.3 ± 2.9(18.0) h/week in the second- (weeks 13-28), and 8.8 ± 4.4(9.6) h/week in the third trimester (weeks 29-40). Endurance training time was distributed into 10.9 ± 6.2(9.9), 15.2 ± 2.3(15.6), and 7.6 ± 3.8(7.9) LIT and 0.4 ± 0.5(0.0), 1.3 ± 0.4(1.4), and 0.7 ± 0.6(0.8) h/week MIT during the three trimesters. Only 2.2 h of HIT was performed during the entire pregnancy. During the first two trimesters, the distribution of exercise modes were approximately the same as pre-pregnancy, but the amount of running was reduced during the third trimester. Training volume during the postpartum periods 1-4 was 6.6 ± 3.8(7.1) (PP1; weeks 1-6), 14.1 ± 3.4(14.3) (PP2; weeks 7-12), 10.6 ± 3.8(10.4) (PP3; weeks 13-18), and 13.6 ± 4.1(14.5) h/week (PP4; weeks 19-24), respectively. Training during PP3 and PP4 was interfered with two fractions in the sacrum, leading to decreased amount of running and MIT/HIT, compensated by increased amounts of cycling. Thereafter, training volume progressively approached the pre-pregnancy values, being 18.0 ± 3.9(18.7) h/week during the general preparation- (weeks 25-44), 17.6 ± 4.4(17.3) h/week during the specific preparation- (weeks 45-53), and 16.9 ± 3.5(17.2) h/week during the competition period (CP; weeks 54-61) leading up to the subsequent world championship. The oxygen uptake at the estimated lactate threshold (LT) decreased to 90% of pre-pregnancy values in the second trimester, but remained to ∼100% in PP3. Body weight and fat-% was higher, while lean body mass and bone mineral density was lower after delivery compared to pre-pregnancy. These measurements gradually changed and were back to ∼pre-pregnancy values during CP. This study indicates that high-level cross country skiers can tolerate high training loads during pregnancy. Although the participant had some postpartum setbacks in her training due to fractures in the sacrum, reduced overall training load, followed by a slower progression and utilization of alternative exercise modes, led to a successful return to competitions.

Changes in foot plantar pressure in pregnant women

BACKGROUND

During pregnancy, the body undergoes many hormonal and anatomical changes causing several medical problems as the musculoskeletal system problems.

OBJECTIVE

To investigate the plantar pressure distribution during pregnancy.

SUBJECTS

Twenty two pregnant and non-pregnant females were selected from the King Abdulaziz University in Jeddah.

METHODS

All females were evaluated by inspection regarding their deformities of the spine, pelvis, lower extremities and feet. Pain was assessed by the Visual Analog Scale (VAS), and the weight and height were recorded using a calibrated weighing scale. Finally, the plantar pressure distribution was examined by a Global Postural Analysis device (GPA).

RESULTS

The results revealed significant asymmetry of weight bearing in the study group (pregnant) compared to the control group (non-pregnant) (p< 0.05). In addition, there was a significant increase in pain intensity in the study group (p= 0.02). On the other hand, the results showed a non-significant difference between study and control groups regarding the three points of pressure (calcaneus, 1st metatarasal and 5th metatarsal) (p> 0.05). Moreover, there was a significant direct relationship between the month of pregnancy and increased weight bearing on the 5th metatarsal in the study group (p= 0.04).

CONCLUSION

There is an effect of pregnancy on plantar pressure distribution as well as weight symmetry which should be considered when designing an antenatal program.

Impact of pregnancy on back pain and body posture in women

[Purpose] The purpose of this single-center investigation was to study the impact of pregnancy on back pain and body posture. [Subjects] The subjects were 26 pregnant females. [Methods] Data were generated with a spine scanner (Diers(®) formetric 4D), trunk strength measurement (Diers(®) myoline), a numeric pain scale (0 to 10), and a biomechanical model. Parameters were compared during each trimester. [Results] The alteration in pain level at rest and lumbar lordosis angle in the females revealed a statistical trend during pregnancy. Spearman's test showed positive correlations between body weight and trunk inclination during the second trimester, and between body weight and the kyphosis angle in the third trimester. The trunk inclination and the kyphosis angle revealed a negative correlation in the third trimester. Based on our analysis, the highest moments and muscle strength must be expended in the third trimester. The actual muscle strength is greatest in the second trimester. [Conclusion] Pain at rest must be given greater attention in pregnant females, and their increasing lumbar kyphosis must be counteracted. Exercising the deep segmental muscles may serve as a preventive measure.

Effects of an aquatic physical exercise program on glycemic control and perinatal outcomes of gestational diabetes: study protocol for a randomized controlled trial

Background

Gestational diabetes mellitus (GDM) is increasing worldwide and has been associated with adverse perinatal outcomes and high risk for chronic disease both for the mother and for the child. Physical exercise is feasible for diabetic pregnant women and contributes to better glycemic control and to a decrease in adverse perinatal outcomes. However, there are no randomized controlled trials (RCT) assessing the effects of aquatic physical exercise on GDM control and adverse maternal and fetal outcomes.

Methods/Design

An RCT will be conducted at Instituto de Medicina Integral Prof Fernando Figueira (IMIP), Brazil. A total of 72 pregnant women will be studied; 36 gestational diabetics will undergo an aquatic physical exercise program in a thermal pool, 3 times per week over 2 months. The primary endpoint will be glucose level control and use of insulin; secondary endpoints will be the following maternal and fetal outcomes: weight gain during pregnancy, blood pressure, pre-eclampsia diagnosis, intrauterus growth restriction, preterm birth, Cesarean section, macrosomia and maternal or neonatal intensive care admission. Endpoints between intervention and control group will analyzed by t test for unpaired data and χ² test, and the level of significance will set at <0.05.

Discussion

The physical proprieties of water make aquatic exercises ideal for pregnant women. An aquatic physical exercise program developed for GDM women will be trialed in a thermal pool and under the supervision of physiotherapist to ensure compliance. It is expected that this study will provide evidence as to the effect of aquatic physical exercise on GDM control.

Trial registration

ClinicalTrial.gov, NCT01940003.

Evidences that maternal swimming exercise improves antioxidant defenses and induces mitochondrial biogenesis in the brain of young Wistar rats

Physical exercise during pregnancy has been considered beneficial to mother and child. Recent studies showed that maternal swimming improves memory in the offspring, increases hippocampal neurogenesis and levels of neurotrophic factors. The objective of this work was to investigate the effect of maternal swimming during pregnancy on redox status and mitochondrial parameters in brain structures from the offspring. Adult female Wistar rats were submitted to five swimming sessions (30 min/day) prior to mating with adult male Wistar rats, and then trained during the pregnancy (five sessions of 30-min swimming/week). The litter was sacrificed when 7 days old, when cerebellum, parietal cortex, hippocampus, and striatum were dissected. We evaluated the production of reactive species and antioxidant status, measuring the activities of superoxide-dismutase (SOD), catalase (CAT) and glutathione-peroxidase (GPx), as well as non-enzymatic antioxidants. We also investigated a potential mitochondrial biogenesis regarding mitochondrion mass and membrane potential, through cytometric approaches. Our results showed that maternal swimming exercise promoted an increase in reactive species levels in cerebellum, parietal cortex, and hippocampus, demonstrated by an increase in dichlorofluorescein oxidation. Mitochondrial superoxide was reduced in cerebellum and parietal cortex, while nitrite levels were increased in cerebellum, parietal cortex, hippocampus, and striatum. Antioxidant status was improved in cerebellum, parietal cortex, and hippocampus. SOD activity was increased in parietal cortex, and was not altered in the remaining brain structures. CAT and GPx activities, as well as non-enzymatic antioxidant potential, were increased in cerebellum, parietal cortex, and hippocampus of rats whose mothers were exercised. Finally, we observed an increased mitochondrial mass and membrane potential, suggesting mitochondriogenesis, in cerebellum and parietal cortex of pups subjected to maternal swimming. In conclusion, maternal swimming exercise induced neurometabolic programing in the offspring that could be of benefit to the rats against future cerebral insults.

Effect of intensive counselling on physical activity in pregnant women at high risk for gestational diabetes mellitus. A clinical study in primary care

OBJECTIVE

The level of physical activity (PA) of pregnant women in Finland is unknown. Even more limited is our knowledge of PA of women at high risk for gestational diabetes mellitus (GDM).

METHODS

The women (n=54) were randomly assigned to a lifestyle intervention group (n=27) including exercise advice by a physiotherapist six times during pregnancy or to a control group (n=27) without additional exercise advice. Outcomes of the present study were required sample size, timing of counselling and change of PA. PA was retrospectively reported during 12 months before pregnancy and recorded one week monthly during pregnancy.

RESULTS

Individualized counselling by a physiotherapist resulted in small changes of recreational PA (2.7 MET hours/week, p=0.056) up to gestational week 25 compared with the similar decreasing tendency of PA in the control group. The women decreased recreational PA after week 30. Sample size of 550 women at high risk for GDM per group would be needed for a PA study.

CONCLUSIONS

The optimal time window for increasing PA must be earlier than in the last trimester of pregnancy. Sample size for a study to increase PA by 2.7 MET hours/week on pregnant women at high risk of GDM should be about 550 per group.

Exercise and pregnancy knowledge among healthcare providers

AIM

To examine healthcare provider knowledge, beliefs, and practices regarding exercise during pregnancy using a cross-sectional 31-question pen and paper survey.

METHODS

Ninety-three practicing healthcare providers, M.D. (n = 45) and D.O. (n = 14) physicians and certified nurse midwives (C.N.M., n = 34), from hospitals and birth centers around Michigan participated in this study. Descriptive characteristic data, provider knowledge, beliefs, and practices regarding exercise during pregnancy, common exercise restrictions given to pregnant patients, and provider awareness of current American College of Obstetricians and Gynecologists (ACOG) exercise and pregnancy guidelines were collected. Descriptive statistics and chi-square analyses were completed.

RESULTS

Overall, 99% of respondents believed that exercise during pregnancy is beneficial, 64% of all respondents believed that maternal exercise heart rate should not exceed 140 beats per minute (bpm), and 60% of M.D.s and 86% of D.O.s were not familiar with the 1994 ACOG guidelines for exercise and pregnancy (p < 0.05).

CONCLUSIONS

Although the providers' beliefs about exercise during pregnancy were positive, not all were aware of or followed current ACOG recommendations. Different strategies for dissemination of current research may be warranted.

Prevalence of lower back pain and physical inactivity: the impact of psychosocial factors in pregnant women served by the Family Health Strategy

ABSTRACT Objective: This study analyzed the impact of psychosocial factors on pregnant women with lower back pain and an associated lack of physical activity prior to pregnancy. Methods: The sample included 66 pregnant women who were randomly selected from a total of 84 patients in the waiting rooms of the Family Health Units in Cuitegí, Paraíba, from September to November 2009. An epidemiological questionnaire adapted from the Quebec Back Pain Disability Scale was used for data collection. The questions about back pain, physical activity, and psychosocial factors were emphasized. SPSS 16.0 was used for the data analysis. The prevalence of lower back pain and its relationship to gestational age, habitual physical activity, and psychosocial factors were studied using the descriptive statistics and relative percentages in the SPSS Crosstabs procedure. The odds ratio and 95% confidence interval for lower back pain were calculated. Results: The prevalence of lower back pain was 75%, which suggests that psychosocial factors were related to the presence of pain. Anxiety was reported in 42.8% of the women with lower back pain, and 38.7% of the women with lower back pain experienced physical fatigue at the end of the day. A higher percentage of pain (53%) was noted in the women who did not exercise prior to pregnancy. Conclusion: Lower back pain prior to pregnancy is associated with lack of physical activity and with psychosocial factors in the Family Health Strategy patients of Cuitegí county.

Water exercises and quality of life during pregnancy

BACKGROUND

In Brazil, concern with the quality of life of pregnant women is one of the points emphasized in the Program for the Humanization of Prenatal Care and Childbirth launched in 2000. However, there are few references in the literature on the role of either land or water-based physical exercise on women's quality of life during pregnancy. The purpose of this study was to evaluate the effects of a physical exercise program of water aerobics on the quality of life (QOL) of sedentary pregnant women.

METHODS

A comparative observational study involving sedentary low-risk pregnant women bearing a single fetus with gestational age less than 20 weeks at the time of admission to the study, who were receiving antenatal care at a public health service. One group of 35 women was given routine antenatal care, while another group of 31 women, in addition to receiving the same routine care as the first group, also participated in three classes of water aerobics per week. QOL was evaluated by applying the WHOQOL-BREF questionnaire in both groups at the 20th, 28th and 36th weeks of pregnancy. In the same occasions, women also answered another questionnaire about their experience with pregnancy and antenatal care.

RESULTS

The great majority of the participants considered that the practice of water aerobics had benefitted them in some way. QOL scores were found to be high in both groups during follow-up. There was no association between the practice of water aerobics and QOL.

CONCLUSIONS

Further studies involving larger sample sizes should be conducted in different sociocultural contexts and/or using other instruments to adequately evaluate the QOL of women during pregnancy.

Feasibility of a lifestyle intervention in early pregnancy to prevent deterioration of glucose tolerance

Background

In conjunction with the growing prevalence of obesity and the older age of pregnant women gestational diabetes (GDM) is a major health problem.

The aim of the study was to evaluate if a lifestyle intervention since early pregnancy is feasible in improving the glucose tolerance of women at a high-risk for GDM in Finland.

Methods

A 75-g oral glucose tolerance test (OGTT) was performed in early pregnancy (n = 102). Women at high risk for GDM (n = 54) were randomized at weeks 8-12 from Apr 2005 to May 2006 to a lifestyle intervention group (n = 27) or to a close follow-up group (n = 27). An OGTT was performed again at weeks 26-28 for the lifestyle intervention and close follow-up groups.

Results

The values of the OGTT during the second trimester did not differ between the lifestyle intervention and close follow-up groups. In the lifestyle intervention group three women had GDM in the second trimester and respectively one woman in the close follow up group. Insulin therapy was not required in both groups. The intervention resulted in somewhat lower weight gain 11.4 ± 6.0 kg vs. 13.9 ± 5.1 kg, p = 0.062, adjusted by the prepregnancy weight.

Conclusions

Early intervention with an OGTT and simple lifestyle advice is feasible. A more intensive lifestyle intervention did not offer additional benefits with respect to glucose tolerance, although it tended to ameliorate the weight gain.

Trial Registration

ClinicalTrials.gov: NCT01130012

Aquatic therapy: scientific foundations and clinical rehabilitation applications

The aquatic environment has broad rehabilitative potential, extending from the treatment of acute injuries through health maintenance in the face of chronic diseases, yet it remains an underused modality. There is an extensive research base supporting aquatic therapy, both within the basic science literature and clinical literature. This article describes the many physiologic changes that occur during immersion as applied to a range of common rehabilitative issues and problems. Because of its wide margin of therapeutic safety and clinical adaptability, aquatic therapy is a very useful tool in the rehabilitative toolbox. Through a better understanding of the applied physiology, the practitioner may structure appropriate therapeutic programs for a diverse patient population.

Dietary intake, weight gain, and birth outcomes of physically active pregnant women: a pilot study

Pregnant women have increased energy and nutrient needs. Exercise also increases energy and glucose demands. This pilot study examined whether women who were physically active during pregnancy met their dietary needs, gained weight adequately, avoided hypoglycemia, and had normal birth outcomes. Based on a convenience sample, 11 active women were studied from 18 weeks gestation to delivery. They exercised for 40 min at 70% VO2 peak, 3-4 times per week. Weekly measures included capillary blood glucose concentrations, body mass, and food records. Birth outcome measures included baby mass, length, and activity, pulse, grimace, appearance, and respiration (APGAR) scores. Our findings suggest that these subjects had lower average energy intake (8680 +/- 490 kJ/d) than recommended for the 2nd and 3rd trimesters (13,020 +/-185 kJ/d; 13,480 +/- 185 kJ/d, respectively, p < 0.0001). Protein requirements for pregnancy were exceeded. Average intakes of iron (19 +/- 2 mg/d) and folate (356 +/- 33 microg/d) were lower than Recommended Dietary Allowances (RDAs) (27 mg/d and 600 microg/d, respectively) and milk products consumed were less than the recommended daily servings. Four women gained less weight per week than recommended for pregnancy. No hypoglycemia occurred post-exercise. Birth outcome measures were within normal ranges. Comparative studies with a larger number of subjects are required to determine if active pregnant women have adequate nutrient intakes and weight gain.

Maternal swimming during pregnancy enhances short-term memory and neurogenesis in the hippocampus of rat pups

In the present study, the effects of maternal swimming during pregnancy on the short-term memory ability, hippocampal neurogenesis, and brain-derived neurotrophic factor (BDNF) mRNA expression of rat pups were investigated. After confirming their pregnancy, the pregnant rats were divided into two groups: the control group and the swimming group. From the 15th day of pregnancy until delivery, pregnant rats were subcutaneously injected with 100mg/kg of 5-bromo-2'-deoxyuridine (BrdU) once a day at 30min before the starting of swimming exercise. Pregnant rats in the swimming group were forced to swim for 10min once a day until delivery. On the 21 days after birth, the rat pups were trained in a step-down avoidance test. The latency time of the step-down avoidance task was determined on the 28 days after birth in order to evaluate the short-term memory ability of pups. On the 29 days after birth, the rat pups' brains were removed, and BrdU immunohistochemistry for the detection of neurogenesis and reverse transcription-polymerase chain reaction (RT-PCR) for the detection of BDNF mRNA expression were then performed. The rat pups born from the maternal rats that performed swimming during pregnancy showed significantly increased BDNF mRNA expression, enhanced hippocampal neurogenesis, and improved short-term memory capability. The present results have clearly shown that maternal swimming by rats during pregnancy enhances the memory of the rats' offspring by increasing neurogenesis. Our present study provides the evidence that maternal exercise during the gestational period may enhance the brain functions of the mothers' offspring.

Swimming of pregnant rats at different water temperatures

We studied the chronic effect of exercise during water immersion, associated with thermal stress (water temperature at 22, 35 and 40 degrees C) at an intensity of 80% of maximal work load supported in pregnant rats (P) and non-pregnant female rats (NP). P and NP were subdivided into three subgroups according to water temperature during exercise (P22 and NP22; P35 and NP35; P40 and NP40). The animals were submitted to daily swimming sessions of 10-15 min, for 19 days of pregnancy (P) or experimental conditions (NP). Plasma concentration of triglycerides, cholesterol, glucose, total protein, albumin and corticosterone were determined 24 h after the last exercise session. Weight gain and rectal temperature pre- and post-swimming session were also determined. The offspring were examined just after caesarian section on the 20th day of pregnancy to check weight, length and litter size. Pregnant rats showed an increase of triglycerides, reduction of glycemia, total protein and albumin and cholesterol (at 35 degrees C) when compared to non-pregnant animals. Such effects probably lead to an adequate delivery of substrate to the fetus and prepare the mother for lactation. Daily thermal stress did not modify metabolic responses to exercise in pregnant rats. Results also show a deleterious effect on offspring when the mother is exposed daily to extreme temperatures during swimming. These results suggest that water temperature (cold and hot) in swimming have to be considered to avoid damage in fetal development.

Thermal response to submaximal exercise before, during and after pregnancy: a longitudinal study

BACKGROUND

Heat stress in early pregnancy is known to have a teratogenic effect. Exercise produces excess heat and during pregnancy might therefore present a theoretical risk of malformations. Our aim was to assess the thermal response to exercise of healthy pregnant women in a longitudinal study.

METHODS

Fourteen women were examined before pregnancy, and followed five times during, and twice after pregnancy, using a submaximal bicycle test with a target heart rate of 85% of the predicted age-adjusted maximum. The main aim was to present reference values.

RESULTS

The temperature at submaximal work load declined continuously from preconception to postpartum levels (37.8 degrees C vs. 36.9 degrees C, p = 0.04). The difference between peak and basal core temperature fell from 0.6 degrees C to 0.05 degrees C at 29 and 36 weeks of gestation, reaching preconception levels at 24 weeks after delivery (0.8 degrees C lower).

CONCLUSION

During submaximal exercise the temperature response seemed to provide thermal protection for the embryo and the fetus.

Position of the American Dietetic Association: nutrition and lifestyle for a healthy pregnancy outcome

It is the position of the American Dietetic Association that women of childbearing potential should maintain good nutritional status through a lifestyle that optimizes maternal health and reduces the risk of birth defects, suboptimal fetal growth and development, and chronic health problems in their children. The key components of a health-promoting lifestyle during pregnancy include appropriate weight gain; consumption of a variety of foods in accordance with the Food Guide Pyramid; appropriate and timely vitamin and mineral supplementation; avoidance of alcohol, tobacco, and other harmful substances; and safe food-handling. Prenatal weight gain within the Institute of Medicine (IOM) recommended ranges is associated with better pregnancy outcomes. The total energy needs during pregnancy range between 2,500 to 2,700 kcal a day for most women, but prepregnancy body mass index, rate of weight gain, maternal age, and physiological appetite must be considered in tailoring this recommendation to the individual. The consumption of more food to meet energy needs and the increased absorption and efficiency of nutrient utilization that occurs in pregnancy are generally adequate to meet the needs for most nutrients. However, vitamin and mineral supplementation is appropriate for some nutrients and situations. This statement also includes recommendations pertaining to use of alcohol, tobacco, caffeine, street drugs, and other substances during pregnancy; food safety; and management of common complaints during pregnancy and specific health problems. In particular for medical nutrition therapy, pregnant women with inappropriate weight gain, hyperemesis, poor dietary patterns, phenylketonuria (PKU), certain chronic health problems, or a history of substance abuse should be referred to a qualified dietetics professional.

SMA statement the benefits and risks of exercise during pregnancy. Sport Medicine Australia

There are numerous benefits to pregnant women of remaining active during pregnancy. These include improved weight control and maintenance of fitness. There may also be benefits in terms of reduced risk of development of gestational diabetes meilitus and improved psychological functioning. Moderate intensity aerobic exercise has been shown to be safe in pregnancy, with a number of studies now indicating that for trained athletes it may be possible to exercise at a higher level than is currently recommended by the American College of Obstetricians and Gynecologists. Studies of resistance training, incorporating moderate weights and avoiding maximal isometnc contractions, have shown no adverse outcomes. There may be benefits of increased strength and flexibility. The risk of neural tube defects due to exercise-induced hyperthermia that is suggested by animal studies is less likely in women, because of more effective mechanisms of heat dissipation in humans. There is accumulating evidence to suggest that participation in moderate intensity exercise throughout pregnancy may enhance birth weight, while more severe or frequent exercise, maintained for longer into the pregnancy: may result in lighter babies. There have been no reports of foetal injury or death in relation to trauma or contact during sporting activities. Despite this, a risk of severe blunt trauma is present in some sporting situations as pregnancy progresses. Exercise and lactation are compatible in the post-partum period, providing adequate calories are consumed. Considerations of pelvic floor function and type of delivery are relevant in planning a return to certain types of exercise at this time.

The benefits of physical activity during pregnancy

The aims of this paper are (1) to comment on the evidence relating to the health risks and benefits of physical activity (PA) for pregnant women and their unborn foetuses. and (2) to discuss the public health benefits of participation in appropriate physical activity during pregnancy. Evidence from recent original research and review papers suggests that there are potential benefits of appropriate PA in terms of maternal weight control and fitness, which are likely to have significant long term public health benefits. Concerns about the potential ill-effects of PA during pregnancy, such as hyperthermia, shortened gestational age and decreased birth weight are not supported by the most recent scientific reviews. The physiological adaptations to exercise during pregnancy appear to protect the foetus from potential harm and, while an upper level of safe activity has not been established, the benefits of continuing to be active during pregnancy appear to outweigh any potential risks. All decisions about participation in physical activity during pregnancy should however be made by women in consultation with their medical advisers.