Bone mineral density changes during pregnancy in actively exercising women as measured by quantitative ultrasound

Physical fitness and maternal body composition indices during pregnancy and postpartum: the GESTAFIT project

We explored the association of physical fitness (PF) during pregnancy with maternal body composition indices along pregnancy and postpartum period. The study comprised 159 pregnant women (32.9 ± 4.7 years old). Assessments were carried out at the 16th and 34th gestational weeks (g.w.) and six weeks postpartum. Cardiorespiratory fitness (CRF), muscular strength (absolute and relative values) and flexibility were measured. Body composition indices were obtained by using dual-energy X-ray absorptiometry at postpartum. The results, after adjusting for potential covariates at the 16th g.w., indicated that greater CRF was associated with lower postpartum indices total fat mass, android and gynoid fat mass (all, p < 0.05). Greater absolute upper-body muscular strength was associated with greater pre-pregnancy body mass index (BMI), gestational weight gain (GWG); and postpartum indices body weight, BMI, lean mass, fat free mass, fat mass, gynoid fat mass, T-score and Z-score bone mineral density (BMD) (all, p < 0.05). Greater upper-body flexibility was associated with lower pre-pregnancy BMI; and postpartum indices body weight, BMI, lean mass, fat free mass, fat mass, android fat mass and gynoid fat mass, and with greater GWG (all, p < 0.05). At the 34th g.w., greater CRF was additionally associated with greater postpartum T-score and Z-score BMD (both, p < 0.05). In conclusion, this study reveals that greater PF levels, especially during early pregnancy, may promote a better body composition in the postpartum period. Therefore, clinicians and health promoters should encourage women to maintain or improve PF levels from early pregnancy.

Bone Health Assessed by Calcaneal Quantitative Ultrasound among Cohort of Pregnant Egyptian Women

Aim

The aim was to assess the risk of osteopenia and osteoporosis and to identify possible risk factors affecting bone density (BD) during pregnancy as parity, body mass index (BMI), Vitamin D, and calcium supplementation using quantitative ultrasound (QUS) of the calcaneus among first- and third-trimester pregnant women.

Methods

It is a case-control study conducted at Ain Shams Maternity Hospital, Egypt, from May 7 to December 14, 2015. One hundred and thirty-two women in the third trimester and 33 matched controls in the first trimester were screened for BD at the calcaneus by QUS. Stiffness index (SI), QUS-T, and Z scores were measured.

Results

Comparing both the groups regarding QUS-T score, Z score, and SI showed a statistically significant difference between both groups. Third-trimester participants had lower scores (-0.72 ± 1.0, -0.63 ± 0.99, and 88.53 ± 14.81, respectively) compared to their matched controls (1.05 ± 0.89, 1.16 ± 0.91, and 113.79 ± 12.49, respectively). According to QUS-T scores, 82 women (62.1%) in the third-trimester group were assessed as having normal BD, whereas 47 women (35.6%) were at risk of being osteopenic and 3 women (2.3%) were at risk of being osteoporotic. All women of the first trimester were assessed as having normal BD. Logistic regression was performed to identify possible risk factors affecting BD among third-trimester patients. BMI was the only statistically significant predictor for changes in bone health in those women (P = 0.001, odds ratio: 0.857, 95% confidence interval: 0.786-0.936).

Conclusion

With one-unit rise in BMI, a 14% reduction in risk of decreased bone health is obtained.

Maternal bone adaptation to mechanical loading during pregnancy, lactation, and post-weaning recovery

The maternal skeleton undergoes dramatic bone loss during pregnancy and lactation, and substantial bone recovery post-weaning. The structural adaptations of maternal bone during reproduction and lactation exert a better protection of the mechanical integrity at the critical load-bearing sites, suggesting the importance of physiological load-bearing in regulating reproduction-induced skeletal alterations. Although it is suggested that physical exercise during pregnancy and breastfeeding improves women's physical and psychological well-being, its effects on maternal bone health remain unclear. Therefore, the objective of this study was to investigate the maternal bone adaptations to external mechanical loading during pregnancy, lactation, and post-weaning recovery. By utilizing an in vivo dynamic tibial loading protocol in a rat model, we demonstrated improved maternal cortical bone structure in response to dynamic loading at tibial midshaft, regardless of reproductive status. Notably, despite the minimal loading responses detected in the trabecular bone in virgins, rat bone during lactation experienced enhanced mechano-responsiveness in both trabecular and cortical bone compartments when compared to rats at other reproductive stages or age-matched virgins. Furthermore, our study showed that the lactation-induced elevation in osteocyte peri-lacunar/canalicular remodeling (PLR) activities led to enlarged osteocyte lacunae. This may result in alterations in interstitial fluid flow-mediated mechanical stimulation on osteocytes and an elevation in solute transport through the lacunar-canalicular system (LCS) during high-frequency dynamic loading, thus enhancing mechano-responsiveness of maternal bone during lactation. Taken together, findings from this study provide important insights into the relationship between reproduction- and lactation-induced skeletal changes and external mechanical loading, emphasizing the importance of weight-bearing exercise on maternal bone health during reproduction and postpartum.

The inverse association between parity and bone health is independent of lifestyle in postmenopausal Chinese women

This study aimed to investigate the association between parity and bone mineral density in postmenopausal Chinese women, as well as the interference of physical activity and sedentary time on this association. A total of 1,712 participants were enrolled in this study. Participants were separated into three groups according to the number of parities: group 1, 1-2; group 2, 3-4; group 3, ≥5. Physical activity level was assessed according to the International Physical Activity Questionnaire. Calcaneus bone mineral density (BMD) and bone quality were assessed by qualitative ultrasound. As a result, logistic regression showed that compared to that in group 1, the risk of fracture in group 3 was increased significantly (p < 0.001). A greater number of parities was associated with a lower BMD, broadband ultrasonic attenuation (BUA), quantitative ultrasound index (QUI), speed of sound (SOS), and T-score among the three groups after adjustment for age (All p for trend < 0.05). The number of parities was an independent factor negatively correlated with BMD, BUA, QUI, SOS and T-score (All p < 0.05). BMD, BUA, QUI, SOS, and T-score were significantly increased in the physically a participants independent of parity (all p < 0.05), and decreased in the sedentary participants independent of parity (p < 0.05, except BUA). A great number of parities was negatively associated with bone health. Physical activity was positively correlated and sedentary time was negatively correlated with bone health independent of parity.

Mechanical Regulation of the Maternal Skeleton during Reproduction and Lactation

PURPOSE OF REVIEW

This review summarizes recently published data on the effects of pregnancy and lactation on bone structure, mechanical properties, and mechano-responsiveness in an effort to elucidate how the balance between the structural and metabolic functions of the skeleton is achieved during these physiological processes.

RECENT FINDINGS

While pregnancy and lactation induce significant changes in bone density and structure to provide calcium for fetal/infant growth, the maternal physiology also comprises several innate compensatory mechanisms that allow for the maintenance of skeletal mechanical integrity. Both clinical and animal studies suggest that pregnancy and lactation lead to adaptations in cortical bone structure to allow for rapid calcium release from the trabecular compartment while maintaining whole bone stiffness and strength. Moreover, extents of lactation-induced bone loss and weaning-induced recovery are highly dependent on a given bone's load-bearing function, resulting in better protection of the mechanical integrity at critical load-bearing sites. The recent discovery of lactation-induced osteocytic perilacunar/canalicular remodeling (PLR) indicates a new means for osteocytes to modulate mineral homeostasis and tissue-level mechanical properties of the maternal skeleton. Furthermore, lactation-induced PLR may also play an important role in maintaining the maternal skeleton's load-bearing capacity by altering osteocyte's microenvironment and modulating the transmission of anabolic mechanical signals to osteocytes. Both clinical and animal studies show that parity and lactation have no adverse, or a positive effect on bone strength later in life. The skeletal effects during pregnancy and lactation reflect an optimized balance between the mechanical and metabolic functions of the skeleton.

The impact of height on low/reduced bone mineral density in Chinese adolescents aged 12-14 years old: gender differences

Low/reduced bone mineral density (BMD) is an important predictor of childhood fracture. In this article, we presented the prevalence of BMD in Chinese adolescents and, for the first time, demonstrated the gender disparities in the impact of height on BMD.

PURPOSE

To analyze the gender disparities in the association of low/reduced BMD with height in Chinese adolescents at the stage of growth spurt.

METHODS

A total of 8152 adolescents aged 12-14 years old were included based on a cross-sectional study in Tianjin, China. Height and weight were measured with standard equipment. BMD was measured using the method of quantitative ultrasound. Adolescents with Z ≤ - 2.0 or - 2.0 < Z ≤ - 1.0 were defined as "low BMD" or "reduced BMD".

RESULTS

The total low/reduced BMD rate was 22.0% in Chinese adolescents aged 12-14 years old, and boys were more likely to have low/reduced BMD than girls (30.1% vs. 12.9%, P < 0.001). The rate of low/reduced BMD significantly increased with age in boys (P_trend = 0.019), whereas decreased with age in girls (P_trend = 0.018). We found significant interaction effect between gender and height standard deviation score (height-Z) in the association with low/reduced BMD (P_interaction < 0.001). There was a positive association of height-Z among boys (OR = 1.30, 95%CI 1.21-1.39, P < 0.001), meanwhile low/reduced BMD was inversely associated with height-Z among girls (OR = 0.85, 95%CI 0.78-0.94, P < 0.001).

CONCLUSIONS

Our study suggested strong gender disparities in the impact of height on BMD in Chinese adolescents aged 12-14 years old, where the association between low/reduced BMD and height was positive among boys but inverse among girls. The study provides evidence on the early prevention and the risk factor identification of low/reduced BMD and childhood fractures.

The effect of an exercise program in pregnancy on vitamin D status among healthy, pregnant Norwegian women: a randomized controlled trial

BACKGROUND

Vitamin D insufficiency is common in pregnant women worldwide. Regular prenatal exercise is considered beneficial for maternal and fetal health. There is a knowledge gap regarding the impact of prenatal exercise on maternal vitamin D levels. The objective of this study was to investigate whether a prenatal exercise program influenced serum levels of total, free and bioavailable 25-hydroxyvitamin D (25(OH)D) and related parameters. This is a post hoc analysis of a randomized controlled trial with gestational diabetes as the primary outcome.

METHODS

Healthy, pregnant women from two Norwegian cities (Trondheim and Stavanger) were randomly assigned to a 12-week moderate-intensity exercise program (Borg perceived rating scale 13-14) or standard prenatal care. The intervention group (n = 429) underwent exercise at least three times weekly; one supervised group training and two home based sessions. The controls (n = 426) received standard prenatal care, and exercising was not denied. Training diaries and group training was used to promote compliance and evaluate adherence. Serum levels of 25(OH)D, parathyroid hormone, calcium, phosphate, magnesium and vitamin D-binding protein were measured before (18-22 weeks' gestation) and after the intervention (32-36 weeks' gestation). Free and bioavailable 25(OH)D concentrations were calculated. Regression analysis of covariance (ANCOVA) was applied to assess the effect of the training regime on each substance with pre-intervention levels as covariates. In a second model, we also adjusted for study site and sampling month. Intention-to-treat principle was used.

RESULTS

A total of 724 women completed the study. No between-group difference in serum 25(OH)D and related parameters was identified by ANCOVA using baseline serum levels as covariates. The second model revealed a between-group difference in levels of 25(OH)D (1.9, 95% CI 0.0 to 3.8 nmol/L; p = 0.048), free 25(OH)D (0.55, 95% CI 0.10 to 0.99 pmol/L; p = 0.017) and bioavailable 25(OH)D (0.15 95% CI 0.01 to 0.29 nmol/L; p = 0.036). No serious adverse events related to regular exercise were seen.

CONCLUSION

This study, a post hoc analysis, indicates that exercise may affect vitamin D status positively, and emphasizes that women with uncomplicated pregnancies should be encouraged to perform regular exercise.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT00476567 , registered May 22, 2007.

Prenatal exercise for the prevention of gestational diabetes mellitus and hypertensive disorders of pregnancy: a systematic review and meta-analysis

Objective

Gestational diabetes mellitus (GDM), gestational hypertension (GH) and pre-eclampsia (PE) are associated with short and long-term health issues for mother and child; prevention of these complications is critically important. This study aimed to perform a systematic review and meta-analysis of the relationships between prenatal exercise and GDM, GH and PE.

Design

Systematic review with random effects meta-analysis and meta-regression.

Data sources

Online databases were searched up to 6 January 2017.

Study eligibility criteria

Studies of all designs were included (except case studies) if published in English, Spanish or French, and contained information on the Population (pregnant women without contraindication to exercise), Intervention (subjective or objective measures of frequency, intensity, duration, volume or type of exercise, alone [“exercise-only”] or in combination with other intervention components [e.g., dietary; “exercise + co-intervention”]), Comparator (no exercise or different frequency, intensity, duration, volume and type of exercise) and Outcomes (GDM, GH, PE).

Results

A total of 106 studies (n=273 182) were included. ‘Moderate’ to ‘high’-quality evidence from randomised controlled trials revealed that exercise-only interventions, but not exercise+cointerventions, reduced odds of GDM (n=6934; OR 0.62, 95% CI 0.52 to 0.75), GH (n=5316; OR 0.61, 95% CI 0.43 to 0.85) and PE (n=3322; OR 0.59, 95% CI 0.37 to 0.9) compared with no exercise. To achieve at least a 25% reduction in the odds of developing GDM, PE and GH, pregnant women need to accumulate at least 600 MET-min/week of moderate-intensity exercise (eg, 140 min of brisk walking, water aerobics, stationary cycling or resistance training).

Summary/conclusions

In conclusion, exercise-only interventions were effective at lowering the odds of developing GDM, GH and PE.

Influence of maternal physical activity on infant's body composition

BACKGROUND

Physical activity (PA) during pregnancy might contribute to reduce neonatal adiposity, a predictor of metabolic disturbances.

OBJECTIVE

The objective of the study was to evaluate the association between maternal PA intensity and neonatal body composition.

METHODS

Maternal PA measured by accelerometry and nutrition were documented during pregnancy, as well as neonatal body composition by dual-energy X-ray absorptiometry following delivery. Associations between PA at 17 and 36 weeks (time spent in moderate PA (MPA), vigorous PA (VPA) status and their interaction) and neonatal body composition were addressed by multivariate regression analyses.

RESULTS

From 104 women, 50 (48%) and 16 (18%) performed VPA at 17 and 36 weeks of pregnancy. Performing VPA at either time was associated with a decreased birthweight (BW), while only VPA at 17 weeks decreased neonatal adiposity (fat percentage: -2.3 ± 0.8%, p = 0.003). MPA at 36 weeks was associated with an increased lean mass (2.0 ± 0.8 g per min day^-1 , p = 0.012). Significant interactions were found for BW and bone mineral content (BMC). MPA at 17 weeks tended to increase BW, but not BMC, in the no VPA strata. By contrast, high levels of MPA (≥112 min d^-1 ) combined with VPA at 17 weeks reduced neonatal BMC and BW compared with no VPA (BMC: -5.4 ± 2.0 g, p = 0.008, BW: -302.8 ± 83.7 g, p = 0.0003). Differences were not significant with low MPA levels.

CONCLUSIONS

Exercise intensity modulates neonatal body composition. The long-term significance of a reduced BW, adiposity and BMC with VPA requires further study.

Clinical Evaluation of Bone Strength and Fracture Risk

PURPOSE OF REVIEW

This paper seeks to evaluate and compare recent advances in the clinical assessment of the changes in bone mechanical properties that take place as a result of osteoporosis and other metabolic bone diseases and their treatments.

RECENT FINDINGS

In addition to the standard of DXA-based areal bone mineral density (aBMD), a variety of methods, including imaging-based structural measurements, finite element analysis (FEA)-based techniques, and alternate methods including ultrasound, bone biopsy, reference point indentation, and statistical shape and density modeling, have been developed which allow for reliable prediction of bone strength and fracture risk. These methods have also shown promise in the evaluation of treatment-induced changes in bone mechanical properties. Continued technological advances allowing for increasingly high-resolution imaging with low radiation dose, together with the expanding adoption of DXA-based predictions of bone structure and mechanics, as well as the increasing awareness of the importance of bone material properties in determining whole-bone mechanics, lead us to anticipate substantial future advances in this field.

An in-school exercise intervention to enhance bone and reduce fat in girls: the CAPO Kids trial

The CAPO Kids trial was a 9-mo, controlled, school-based intervention to examine the effects of a novel, brief, high intensity exercise regime on indices of musculoskeletal and metabolic health in pre- and early-pubertal girls.

METHODS

A total of 151 pre- and early-pubertal girls (10.6±0.6years), recruited from two different schools consented to participate; 76 in the exercise group (EX) and 75 in the control group (CON). EX performed 10min bouts of thrice-weekly jumping plus capoeira (a Brazilian sport that combines martial art with dance), along with usual physical education (PE) activities. CON continued usual PE alone. Maturity, weight, height, waist circumference, resting heart rate and blood pressure, maximal vertical jump, and aerobic capacity were determined using standard clinical and field measures. Calcaneal broadband ultrasound attenuation (BUA) and stiffness index (SI) were determined from quantitative ultrasonometry. A subsample of children also underwent DXA and pQCT measures. Prior physical activity participation and daily calcium consumption were determined from validated instruments.

RESULTS

EX girls improved BUA more than CON (+4.5% vs. +1.4%, p=0.019). Resting heart rate (-7.2% vs. -1.8%, p<0.01), maximal vertical jump (+13.4% vs. -1.2%, p<0.001), estimated maximal oxygen consumption (+10.6% vs. +1.0%, p<0.001), and waist circumference (+2.7% vs. +5.6%, p<0.001) also improved more for EX than CON.

CONCLUSION

Ten minutes of high intensity exercise (capoeira and jumping) three times a week in the primary school setting enhances musculoskeletal and metabolic outcomes in pre- and early-pubertal girls without disrupting the academic schedule. The programme, amenable to broad-scale school implementation, would confer meaningful public health benefits.

Benefits of exercise during pregnancy

There is a direct link between healthy mothers and healthy infants. Exercise and appropriate nutrition are important contributors to maternal physical and psychological health. The benefits and potential risks of exercise during pregnancy have gained even more attention, with a number of studies having been published after the 2002 American College of Obstetrics and Gynecologists guidelines. A review of the literature was conducted by using PubMed, Scopus, and Embase to assess the literature regarding the benefits of exercise during pregnancy. The search revealed 219 publications, which the authors then narrowed to 125 publications. The purpose of this review is to briefly summarize the known benefits of exercise to the mother, fetus, and newborn.