Longitudinal changes in bone mineral density during normal pregnancy

Longitudinal changes of the femoral bone mineral density from first to third trimester of pregnancy: bone health assessment by means of non-ionizing REMS technology

BACKGROUND

Throughout the pregnancy, there is a substantial transfer of calcium from the maternal skeleton to the fetus, which leads to a transient net reduction of the maternal bone mineral density.

AIMS

To assess longitudinally the changes in the bone mineral density at the femoral neck between the first and third trimester of pregnancy in a cohort of healthy participants using Radiofrequency Echographic Multi Spectrometry (REMS) technology.

METHODS

Prospective, cohort study conducted at the University hospital of Parma, Italy between July 2022 and February 2023. We recruited healthy participants with an uncomplicated singleton pregnancy before 14 completed weeks of gestation. All included participants were submitted to a sonographic examination of the femoral neck to assess the bone mineral density (and the corresponding Z-score values) using REMS at 11-13 and 36-38 weeks of pregnancy. The primary outcome was the change in the bone mineral density values at the maternal femoral neck between the first and third trimester of pregnancy.

RESULTS

Over a period of 7 months, a total of 65 participants underwent bone mineral density measurement at the femoral neck at first and third trimester of the pregnancy using REMS. A significant reduction of the bone mineral density at the femoral neck (0.723 ± 0.069 vs 0.709 ± 0.069 g/cm2; p < 0.001) was noted with a mean bone mineral density change of - 1.9 ± 0.6% between the first and third trimester of pregnancy. At multivariable linear regression analysis, none of the demographic or clinical variables of the study population proved to be independently associated with the maternal bone mineral density changes at the femoral neck.

CONCLUSIONS

Our study conducted on a cohort of healthy participants with uncomplicated pregnancy demonstrates that there is a significant reduction of bone mineral density at femoral neck from early to late gestation.

Bone fragility and osteoporosis in children and young adults

Osteoporosis is a metabolic bone disorder which increases fragility fracture risk. Elderly individuals, especially postmenopausal women, are particularly susceptible to osteoporosis. Although rare, osteoporosis in children and young adults is becoming increasingly evident, highlighting the need for timely diagnosis, management and follow-up. Early-onset osteoporosis is defined as the presence of a low BMD (Z-score of ≤ -2.0 in individuals aged < 20 years; T-score of ≤ -2.5 in those aged between 20 to 50 years) accompanied by a clinically significant fracture history, or the presence of low-energy vertebral compression fractures even in the absence of osteoporosis. Affected children and young adults should undergo a thorough diagnostic workup, including collection of clinical history, radiography, biochemical investigation and possibly bone biopsy. Once secondary factors and comorbidities are excluded, genetic testing should be considered to determine the possibility of an underlying monogenic cause. Defects in genes related to type I collagen biosynthesis are the commonest contributors of primary osteoporosis, followed by loss-of-function variants in genes encoding key regulatory proteins of canonical WNT signalling (specifically LRP5 and WNT1), the actin-binding plastin-3 protein (encoded by PLS3) resulting in X-linked osteoporosis, and the more recent sphingomyelin synthase 2 (encoded by SGMS2) which is critical for signal transduction affecting sphingomyelin metabolism. Despite these discoveries, genetic causes and underlying mechanisms in early-onset osteoporosis remain largely unknown, and if no causal gene is identified, early-onset osteoporosis is deemed idiopathic. This calls for further research to unravel the molecular mechanisms driving early-onset osteoporosis that consequently will aid in patient management and individualised targeted therapy.

The influence of lactation and its duration on bone mineral density in pregnancy and postpartum: A systematic review with meta-analysis

BACKGROUND

There is a plethora of research on the association of parity and duration of lactation with bone mineral density (BMD) during and after pregnancy. However, there are no consensus conclusions on the impact of the duration of lactation on BMD.

AIMS

The aim of this study was to examine the effect of pregnancy, and the duration of lactation on BMD during pregnancy, postpartum phase and 12 months post-delivery.

METHODS

The search terms 'parity' 'lactation' 'BMD' were searched for using PubMed, CINAHL, SCOPUS and EMBASE databases in English language. Two independent reviewers assessed the quality of the included studies using Critical Appraisal Skills Program (CASP) appraisal tool and extracted data on BMD (g/cm²) in Excel. A meta-analysis was conducted with a random effect model using Cochrane Review Manager (Rev 5.4) to analyse the outcome. Heterogeneity was assessed with Chi Squared and I² test. The duration of lactation was grouped into short lactation duration (SLD), ≤4 months and longer lactation duration (LLD) > 6 months.

RESULTS

Twenty-one studies were included in this review with four studies included in the meta-analysis. BMD reduced during pregnancy and lactation. Recovery and net gains in BMD followed weaning. However, at 12 months postpartum, women in the LLD group had significant losses at the lumbar spine while those in the SLD recovered BMD. Between the SLD and LLD groups, the change in BMD was not significant 0.48 g/cm² (95% CI -0.14, 1.10, p = 0.13). BMD losses were greater in primiparous women than multiparous women.

CONCLUSION

Women who breastfed for >6 months had significantly reduced BMD. However, compared to women that breastfed for a ≤4 months there was no significant change in BMD. Further investigation is needed to clarify the association between lactation and BMD in a postpartum population in those women extending breastfeeding beyond one year.

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.

Is Supplementation with Micronutrients Still Necessary during Pregnancy? A Review

INTRODUCTION

Proper nutrition during pregnancy is important to prevent nutritional imbalances that interfere with pregnancy. Micronutrients play critical roles in embryogenesis, fetal growth, and maternal health, as energy, protein, vitamin, and mineral needs can increase during pregnancy. Increased needs can be met by increasing the intake of dietary micronutrients. Severe micronutrient deficiency or excess during pregnancy can have negative effects on fetal growth (intrauterine growth retardation, low birth weight, or congenital malformations) and pregnancy development (pre-eclampsia or gestational diabetes). We investigate whether it is necessary to continue micronutrient supplementation during pregnancy to improve women's health in this stage and whether this supplementation could prevent and control pathologies associated with pregnancy.

AIM

The present review aims to summarize evidence on the effects of nutritional deficiencies on maternal and newborn morbidity.

METHODS

This aim is addressed by critically reviewing results from published studies on supplementation with different nutrients during pregnancy. For this, major scientific databases, scientific texts, and official webpages have been consulted. PubMed searches using the terms "pregnancy" OR "maternal-fetal health" AND "vitamins" OR "minerals" OR "supplementation" AND "requirement" OR "deficiency nutrients" were performed.

RESULTS

There are accepted interventions during pregnancy, such as folic acid supplementation to prevent congenital neural tube defects, potassium iodide supplementation to correct neurodevelopment, and oral iron supplementation during the second half of pregnancy to reduce the risk of maternal anemia and iron deficiency. A number of micronutrients have also been associated with pre-eclampsia, gestational diabetes mellitus, and nausea and vomiting in pregnancy. In general, experimental studies are necessary to demonstrate the benefits of supplementation with different micronutrients and to adjust the recommended daily doses and the recommended periconceptional nutrition for mothers.

CONCLUSIONS

Presently, there is evidence of the benefits of micronutrient supplementation in perinatal results, but indiscriminate use is discouraged due to the fact that the side effects of excessive doses are not known. Evidence supports the idea that micronutrient deficiencies negatively affect maternal health and the outcome of pregnancy. No single micronutrient is responsible for the adverse effects; thus, supplementing or correcting one deficiency will not be very effective while other deficiencies exist.

Bone Mineral Density Changes Associated With Pregnancy, Lactation, and Medical Treatments in Premenopausal Women and Effects Later in Life

Bone mineral density (BMD) changes during the life span, increasing rapidly during adolescence, plateauing in the third decade of life, and subsequently entering a phase of age-related decline. In women, menopause leads to accelerated bone loss and an increase in fracture risk. Between peak bone mass attainment and menopause, BMD is generally stable and the risk of fracture is typically low. This time period is marked by life events such as pregnancy and lactation, which transiently decrease BMD, yet their long-term effects on fracture risk are less certain. BMD may also be altered by exposure to medications that affect bone metabolism (e.g., contraceptives, glucocorticoids, antidiabetic medications, antiepileptic drugs). Although oral contraceptives are often believed to be neutral with regard to bone health, depot medroxyprogesterone acetate (DMPA) and gonadotropin-releasing hormone (GnRH) agonists have been associated with decreases in BMD. Development of newer medical therapies, principally GnRH antagonists (e.g., ASP1707, elagolix, linzagolix, relugolix), for treatment of endometriosis-associated pelvic pain and heavy menstrual bleeding due to uterine fibroids has renewed interest in the short- and long-term impacts of changes in BMD experienced by premenopausal women. It is important to understand how these drugs influence BMD and put the findings into context with regard to measurement variability and naturally occurring factors that influence bone health. This review summarizes what is known about the effects on bone health pregnancy, lactation, and use of DMPA, GnRH agonists, and GnRH antagonists in premenopausal women and potential consequences later in life. ClinicalTrials.gov identifier: NCT03213457.

Pregnancy-Related Change in pQCT and Bone Biochemistry in a Population With a Habitually Low Calcium Intake

In pregnancy, changes in maternal calcium (Ca) economy occur to satisfy fetal Ca demand. It is unclear whether maternal mineral reserves facilitate these requirements and no data exist from sub-Saharan Africa. The aim was to determine skeletal changes with peripheral quantitative computed tomography (pQCT) and bone biochemistry between early second and third trimesters. Pregnant rural Gambians aged 18 to 45 years (n = 467) participating in a trial of antenatal nutritional supplements (ISRCTN49285450) had pQCT scans and blood collections at mean (SD) 14 (3) and 31 (1) weeks' gestation. Outcomes were pQCT: radius/tibia 4% total volumetric bone mineral density (vBMD), trabecular vBMD, total cross-sectional area (CSA), 33%/38% radius/tibia cortical vBMD, bone mineral content (BMC), total CSA; biochemistry: collagen type 1 cross-linked β-C-telopeptide (β-CTX), type 1 procollagen N-terminal (P1NP), parathyroid hormone (PTH), and 1,25(OH)₂ D. Independent t tests tested whether pooled or within-group changes differed from 0. Multiple regression was performed adjusting for age. Data for change are expressed as mean (confidence interval [CI] 2.5, 97.5%). Radius trabecular vBMD, cortical vBMD, and BMC increased by 1.15 (0.55, 1.75)%, 0.41 (0.24, 0.58)%, and 0.47 (0.25, 0.69)%. Tibia total and trabecular vBMD increased by 0.34 (0.15, 0.54)% and 0.46 (0.17, 0.74)%, while tibia cortical vBMD, BMC, and cortical CSA increased by 0.35 (0.26, 0.44)%, 0.55 (0.41, 0.68)% and 0.20 (0.09, 0.31)%, respectively. CTX, PTH, and 1,25(OH)₂ D increased by 23.0 (15.09, 29.29)%, 13.2 (8.44, 19.34)%, and 21.0 (17.67, 24.29)%, while P1NP decreased by 32.4 (-37.19, -28.17)%. No evidence of mobilization was observed in the peripheral skeleton. Resorption, although higher in late versus early gestation, was lower throughout pregnancy compared with non-pregnant non-lactating (NPNL) in the same community. Formation was lower in late pregnancy than in early, and below NPNL levels. This suggests a shift in the ratio of resorption to formation. Despite some evidence of change in bone metabolism, in this population, with habitually low Ca intakes, the peripheral skeleton was not mobilized as a Ca source for the fetus. © 2021 crown copyright . Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR). The article published with the permission of the Controller of HMSO and the Queen's Printer of Scotland..

Maternal and fetal vitamin D and their roles in mineral homeostasis and fetal bone development

During pregnancy, female physiology adapts to meet the additional mineral demands of the developing fetus. Meanwhile, the fetus actively transports minerals across the placenta and maintains high circulating levels to mineralize the rapidly developing skeleton. Most of this mineral is accreted during the last trimester, including 30 g of calcium, 20 g of phosphate and 0.8 g of magnesium. Given the dependence of calcium homeostasis on vitamin D and calcitriol in the adult and child, it may be expected that vitamin D sufficiency would be even more critical during pregnancy and fetal development. However, the pregnant mother and fetus appear to meet their mineral needs independent of vitamin D. Adaptations in maternal mineral and bone metabolism during pregnancy appear to be invoked independent of maternal vitamin D, while fetal mineral metabolism and skeletal development appear to be protected from vitamin D deficiency and genetic disorders of vitamin D physiology. This review discusses key data from both animal models and human studies to address our current knowledge on the role of vitamin D and calcitriol during pregnancy and fetal development.

Pregnancy-Related Bone Mineral and Microarchitecture Changes in Women Aged 30 to 45 Years

At birth, the neonatal skeleton contains 20 to 30 g calcium (Ca). It is hypothesized maternal bone mineral may be mobilized to support fetal skeletal development, although evidence of pregnancy-induced mineral mobilization is limited. We recruited healthy pregnant (n = 53) and non-pregnant non-lactating (NPNL; n = 37) women aged 30 to 45 years (mean age 35.4 ± 3.8 years) and obtained peripheral quantitative computed tomography (pQCT) and high-resolution pQCT (HR-pQCT) scans from the tibia and radius at 14 to 16 and 34 to 36 weeks of pregnancy, with a similar scan interval for NPNL. Multiple linear regression models were used to assess group differences in change between baseline and follow-up; differences are expressed as standard deviation scores (SDS) ± SEM. Decreases in volumetric bone mineral density (vBMD) outcomes were found in both groups; however, pregnancy-related decreases for pQCT total and trabecular vBMD were -0.65 ± 0.22 SDS and -0.50 ± 0.23 SDS greater (p < .05). HR-pQCT total and cortical vBMD decreased compared with NPNL by -0.49 ± 0.24 SDS and -0.67 ± 0.23 SDS, respectively; trabecular vBMD decreased in both groups to a similar magnitude. Pregnancy-related changes in bone microarchitecture significantly exceeded NPNL change for trabecular number (0.47 ± 0.23 SDS), trabecular separation (-0.54 ± 0.24 SDS), cortical thickness (-1.01 ± 0.21 SDS), and cortical perimeter (0.78 ± 0.23 SDS). At the proximal radius, cortical vBMD and endosteal circumference increased by 0.50 ± 0.23 SDS and 0.46 ± 0.23 SDS, respectively, compared with NPNL, whereas cortical thickness decreased -0.50 ± 0.22 SDS. Pregnancy-related decreases in total and compartment-specific vBMD exceed age-related change at the distal tibia. Changes at the radius were only evident with pQCT at the cortical-rich proximal site and suggest endosteal resorption. Although the magnitude of these pregnancy-related changes in the appendicular skeleton are small, if they reflect global changes across the skeleton at large, they may contribute substantially to the Ca requirements of the fetus. © 2020 Crown copyright. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR). This article is published with the permission of the Controller of HMSO and the Queen's Printer for Scotland.

Pregnancy and lactation, a challenge for the skeleton

In this review we discuss skeletal adaptations to the demanding situation of pregnancy and lactation. Calcium demands are increased during pregnancy and lactation, and this is effectuated by a complex series of hormonal changes. The changes in bone structure at the tissue and whole bone level observed during pregnancy and lactation appear to largely recover over time. The magnitude of the changes observed during lactation may relate to the volume and duration of breastfeeding and return to regular menses. Studies examining long-term consequences of pregnancy and lactation suggest that there are small, site-specific benefits to bone density and that bone geometry may also be affected. Pregnancy- and lactation-induced osteoporosis (PLO) is a rare disease for which the pathophysiological mechanism is as yet incompletely known; here, we discuss and speculate on the possible roles of genetics, oxytocin, sympathetic tone and bone marrow fat. Finally, we discuss fracture healing during pregnancy and lactation and the effects of estrogen on this process.

Inhibited Maternal Bone Resorption Suppress Fetal Rat Bone Development During Pregnancy

Objective

To determine the relationship between maternal bone resorption and bone development in fetuses.

Methods

Female SD rats were injected with either fluorescent calcium indicator calcein alone or together with tetracycline 1 week before pregnancy, followed by fluorescence detection in fetal tibias 21 days post-treatment. Alendronate was subsequently administered to pregnant rats to inhibit maternal bone resorption, while maternal bone turnover and fetal bone development were both examined.

Results

The maternal fluorescent labeled calcium before pregnancy was found in the fetal tibia. This indicated that the calcium of maternal bones may be released into the maternal circulation through high bone resorption during pregnancy, thereby participating in the fetal bone development. Bone histomorphometry and serum biomarker results showed that Alendronate significantly inhibited maternal bone resorption in pregnant rats when compared to normal pregnant rats. Moreover, the body weight, bone mass, and bone length of the fetuses in the Alendronate group were significantly decreased; while no apparent abnormality in placental morphology was observed. The above results implied that when maternal bone resorption is suppressed, the development of the fetal bone shall also be suppressed.

Conclusion

Calcium in the maternal bone is released into the maternal circulation through bone resorption during pregnancy which represents an important material source in fetal bone development. Therefore, high bone turnover during pregnancy is essential for mammalian embryonic bone development.

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.

Changes in bone metabolic profile associated with pregnancy or lactation

Calcium and nutrients are transferred from mothers to fetuses or infants during pregnancy or lactation, respectively, promoting metabolic changes in the mother, many uncharacterized. To evaluate these changes, we undertook two parallel studies. In one we analyzed fourteen clinical cases of vertebral fragility fractures, at or before three months after partum, in mothers who breastfed their infants. In the other, we enrolled 79 additional pregnant subjects, some who chose to breastfeed and others who did not, and analyzed changes in bone metabolic status starting between 34 and 36 weeks of gestation and ending one month after partum. In the larger group, bone-resorbing and bone-forming parameters such as serum TRACP5b and osteocalcin, respectively, significantly increased after partum. Among parameters that changed after partum, serum PTH and the bone-resorbing markers serum TRACP5b and urine NTX were significantly higher in mothers who only breastfed infants compared to mothers who fed infants formula or a mix of both. However, bone-forming parameters were comparable between breastfeeding and non-breast-feeding groups after partum, suggesting that elevated bone-resorption occurs only in the breastfeeding group. Radiographic analysis after partum demonstrated that no subject among the 79 analyzed showed vertebral fractures, even those who breastfed exclusively. Among fracture cases analyzed, subjects exhibited significantly lower bone mineral density than did non-fracture cases in breastfeeding-only subjects. We conclude that bone metabolic status significantly changes over the period between pregnancy and post-partum lactation, and that low bone mineral density seen in a small subset of breastfeeding-only cases likely causes post-partum vertebral fragility fractures.

Effect of prenatal calcium supplementation on bone during pregnancy and 1 y postpartum

Background

Low calcium intake during pregnancy may cause maternal skeletal calcium mobilization to meet fetal needs. The Recommended Dietary Allowance (RDA) for calcium in nonpregnant, pregnant, or lactating women aged 19-50 y is 1000 mg/d; most women in the United States report consuming 60-80% of the calcium RDA. An insufficient calcium intake could increase maternal bone loss during pregnancy and reduce bone recovery postpartum.

Objectives

The aim of this study was to determine the effect of maternal calcium supplementation on peripheral cortical and trabecular bone loss during pregnancy and bone gain postpartum.

Methods

A total of 64 women were enrolled in the study at 16 wk of gestation and randomly assigned to receive 1000 mg Ca/d or placebo for the remainder of the pregnancy. Measurements were performed at 16, 26, and 36 wk of pregnancy and at 4 and 12 mo postpartum for serum 25-hydroxyvitamin D and markers of bone turnover. Trabecular and cortical bone mineral density (BMD) and content were assessed at the tibia and radius by peripheral quantitative computed tomography.

Results

Mean ± SD daily calcium intake at baseline was 733 ± 350 mg; only 25% of the women met the RDA. Thirty women (47% of those enrolled) remained in the study at 12 mo postpartum. After controlling for baseline bone value, serum 25-hydroxyvitamin D concentrations, length of breastfeeding, and body mass index, the calcium group had significantly greater increases in radial total BMD (P = 0.02) and tibial cortical BMD (P = 0.03) at 12 mo postpartum than the placebo group. Trabecular and total BMD at the tibia trended toward higher values (P < 0.06) in the calcium group than in the placebo group in the same models.

Conclusions

These data show that supplemental calcium provided during pregnancy may improve bone recovery postpartum in women consuming a typical US diet. A larger study is warranted to solidify the conclusions. This trial was registered at clinicaltrials.gov as NCT01145573.

Bone mineral density during pregnancy in women participating in a randomized controlled trial of vitamin D supplementation

Background: Little is known about bone mineral density (BMD) during pregnancy. Advances in technology with lower radiation emissions by dual-energy X-ray absorptiometry instruments now permit the safe measurement of BMD during pregnancy.Objective: We evaluated maternal BMD during pregnancy as a function of vitamin D status in women of diverse racial/ethnic backgrounds.Design: A total of 301 women who underwent BMD measurements at 12-20 wk of gestation and again at 0-14 wk postpartum were included in this analysis. Women were a subset of subjects who were recruited for a randomized, controlled, double-blind trial of vitamin D supplementation in pregnancy (400, 2000, or 4000 IU/d).Results: Treatment had no significant effect on changes in BMD that occurred between 12-20 wk of gestation and 0-14 wk postpartum. Similarly, changes in spine and femoral neck bone mineral contents (BMCs) were not significantly different in the treatment groups. In addition, vitamin D inadequacy (serum 25-hydroxyvitamin D concentration, averaged across pregnancy, <50 nmol/L) was not associated with changes in BMD or BMC. There were significant racial/ethnic differences in spine BMD. African Americans lost more spine BMD than did Caucasians (-0.04 ± 0.04 compared with -0.02 ± 0.04 g/cm²; P = 0.033). In addition, baseline obesity was associated with a greater loss of femoral neck BMD. The means ± SDs of femoral neck BMD loss were -0.02 ± 0.05 and 0.0 ± 0.03 g/cm² for groups with baseline body mass index (BMI; in kg/m²) ≥30 and <30, respectively.Conclusion: These findings do not support a dose effect of vitamin D supplementation on bone health and suggest that race/ethnicity and BMI play an important role in pregnancy bone health. This trial was registered at clinicaltrials.gov as NCT00292591.

Pregnancy-related fractures: a retrospective study of a French cohort of 52 patients and review of the literature

A retrospective, multicentre study involving 52 patients was carried out to define the causes and characteristics of pregnancy-related osteoporosis. The mean number of vertebral fractures occurring during the last trimester of pregnancy or at the time of delivery was 3.8. This is often promoted by risk factors before or during pregnancy.

INTRODUCTION

In order to define the causes or predisposing factors of pregnancy-related osteoporosis and its clinical, radiological and bone density characteristics, laboratory findings, course and outcome, we carried out a retrospective multicentre study.

METHODS

The records of 52 women hospitalised over the last 10 years in the rheumatology departments of six French university hospitals and with a diagnosis of pregnancy-related osteoporosis were examined.

RESULTS

The patients' mean age at time of fracture was 32.1 years. In 10 patients, the fractures had occurred during the last trimester of pregnancy, and in 36 at the time of delivery or during the first 2 months post-partum. The mean number of vertebral fractures was 3.8 ± 2.0. Thirty three of the 52 patients had a risk factor of low bone mass before pregnancy. Twelve had disorders or treatments (heparin) that might promote osteoporosis during pregnancy, while 14 had no trigger factors before or during pregnancy. Overall, phosphate and calcium levels were normal, except for hyperphosphoraemia in lactating women (90%). On DXA scan, osteoporosis predominated in the trabecular bone (spinal T-score - 3.4, hip T-score - 2). Only 10 patients had a repeat fracture, and the increase in bone mineral density during follow-up was considerable, and improved by bisphosphonates (annual gain + 10% in the spine) or teriparatide (+ 15%).

CONCLUSIONS

Pregnancy-related osteoporosis gives rise to multiple vertebral fractures. It is often promoted by risk factors before or during pregnancy. Its mechanism is still unknown. Treatment with bisphosphonates or teriparatide appears to improve the recovery of bone mineral density.

Two cases of pregnancy- and lactation- associated osteoporosis successfully treated with denosumab

Case 1. A 35-year-old woman in the 8^th month of her first pregnancy suffered acute lumbar pain that persisted for 4 months. In the 5^th month postpartum an acute increase in the low back pain led to a MRI which showed recent deformity in L1 and deformities of undetermined time of evolution in L2, L4, and L5. Laboratory evaluation did not reveal metabolic derangements. She had low bone mineral density (BMD, DXA) and severe deterioration of the microarchitecture of distal appendicular bone (HR-pQCT). Kyphoplasty of all 4 vertebrae was performed in 2 stages, and treatment with subcutaneous denosumab, 60 mg every 6 months, was begun. There was rapid and almost complete improvement in pain. An increase in trabecular bone was documented with HR-pQCT. Case 2. A 33-year-old mother who was breastfeeding her first-born child experimented acute dorsal pain. RMI revealed partial compression fractures in vertebrae D5-7. Her axial BMD was low. There was no family history of osteoporosis, and causes of secondary osteoporosis were ruled out. Her pain slowly subsided with conservative measures, oral analgesics, and nasal calcitonin. Then, treatment with oral strontium ranelate was prescribed; after 3 months serum alkaline phosphatase and osteocalcin had not increased, and after one year lumbar bone mineral density (BMD) was unchanged. Treatment was switched to subcutaneous denosumab. After one year, lumbar BMD had increased 14%, and the pain had almost completely subsided.

Prevalence of Low Bone Mineral Density and Associated Risk Factors in Korean Puerperal Women

Although pregnancy is a medical condition that contributes to bone loss, little information is available regarding bone mineral density (BMD) in puerperal women. This cross sectional study aimed to evaluate the prevalence of low BMD in puerperal women and to identify associated risk factors. We surveyed all puerperal women who had BMD measurements taken 4-6 weeks after delivery in a tertiary university hospital, and did not have any bone loss-related comorbidities. Among the 1,561 Korean puerperal women, 566 (36.3%) had low BMD at the lumbar spine, total hip, femoral neck, and/or trochanter. Multivariate analysis revealed that underweight women had a significantly higher risk of low BMD compared with obese women at pre-pregnancy (adjusted odds ratio [aOR], 3.21; 95% confidence interval [CI], 1.83-5.63). Also, women with inadequate gestational weight gain (GWG) were 1.4 times more likely to have low BMD than women with excessive GWG (aOR, 1.42; 95% CI, 1.04-1.94). One-way ANOVA showed that BMDs at the lumbar spine and total hip were significantly different between the 4 BMI groups (both P < 0.001) and also between the 3 GWG groups (both P < 0.001). In conclusion, this study identifies a high prevalence of low BMD in puerperal women and thus suggests the need for further evaluation about the change of BMD in pregnancy and postpartum period.

Maternal Mineral and Bone Metabolism During Pregnancy, Lactation, and Post-Weaning Recovery

During pregnancy and lactation, female physiology adapts to meet the added nutritional demands of fetuses and neonates. An average full-term fetus contains ∼30 g calcium, 20 g phosphorus, and 0.8 g magnesium. About 80% of mineral is accreted during the third trimester; calcium transfers at 300-350 mg/day during the final 6 wk. The neonate requires 200 mg calcium daily from milk during the first 6 mo, and 120 mg calcium from milk during the second 6 mo (additional calcium comes from solid foods). Calcium transfers can be more than double and triple these values, respectively, in women who nurse twins and triplets. About 25% of dietary calcium is normally absorbed in healthy adults. Average maternal calcium intakes in American and Canadian women are insufficient to meet the fetal and neonatal calcium requirements if normal efficiency of intestinal calcium absorption is relied upon. However, several adaptations are invoked to meet the fetal and neonatal demands for mineral without requiring increased intakes by the mother. During pregnancy the efficiency of intestinal calcium absorption doubles, whereas during lactation the maternal skeleton is resorbed to provide calcium for milk. This review addresses our current knowledge regarding maternal adaptations in mineral and skeletal homeostasis that occur during pregnancy, lactation, and post-weaning recovery. Also considered are the impacts that these adaptations have on biochemical and hormonal parameters of mineral homeostasis, the consequences for long-term skeletal health, and the presentation and management of disorders of mineral and bone metabolism.

A case series of pregnancy- and lactation-associated osteoporosis and a review of the literature

The syndrome of pregnancy- and lactation-associated osteoporosis is a rare disorder whose precise etiology and treatment are largely unknown. We herein report two such cases occurring in the early postpartum period that led to multiple fragility compression fractures. Combination therapy of vitamin D and vitamin K enabled a marked gradual increase in bone mineral density.

Bone mineral density in treated at a young age for differentiated thyroid cancer after Chernobyl female patients on TSH-suppressive therapy receiving or not Calcium-D3 supplementation

Long-term management of patients with differentiated thyroid cancer (DTC) commonly includes TSH-suppressive therapy with L-T4 and, in case of postsurgical hypoparathyroidism, Calcium-D3 supplementation, both of which may affect skeletal health. Experience with female patients treated for DTC at a young age and who were then receiving long-term therapy with L-T4 and Calcium-D3 medication is very limited to date. This cross-sectional study set out to investigate effects of Calcium-D3 supplementation and TSH-suppressive therapy on bone mineral density (BMD) in 124 young female patients treated for DTC at a mean age of 14 years and followed-up for an average of 10 years. BMD was found to be significantly higher in patients receiving Calcium-D3 medication than in patients not taking supplements. The level of ionized calcium was the strongest factor determining lumbar spine BMD in patients not receiving Calcium-D3 supplementation. Pregnancy ending in childbirth and HDL-cholesterol were associated with a weak adverse effect on spine and femoral BMD. No evidence of adverse effects of L-T4 and of radioiodine therapies on BMD was found. We conclude that Calcium-D3 medication has a beneficial effect on BMD, and that TSH-suppressive therapy does not affect BMD in women treated for DTC at young age, at least after 10 years of follow-up.

Dietary supplementation with long chain polyunsaturated fatty acids in pregnant guinea pigs has sex-dependent effects on growth and bone outcomes in offspring

Long chain PUFA enhance bone mass in non-pregnant mammals. We examined the effects of arachidonic (AA; 20:4n-6) and docosahexaenoic (DHA; 22:6n-3) acid on bone mass of mothers and neonates. Guinea pig sows (n=15) were fed control, DHA or AA+DHA diets from mating to weaning. Measurements included: osteocalcin (OC), deoxypyridinoline (DPD), areal bone mineral density (aBMD) in sows and neonates; and volumetric density (vBMD) in neonates. Only vertebral aBMD and OC:DPD ratio declined during reproduction and only DHA reduced OC:DPD. Male pup weight was reduced by DHA and female weight elevated by AA+DHA. Whole body and femur aBMD were reduced by DHA and AA+DHA; whereas tibia vBMD was reduced by DHA in males. Female whole body, tibia and vertebrae aBMD plus tibia vBMD were elevated by AA+DHA; and DHA elevated whole body, tibia and vertebrae aBMD. Dietary AA+DHA and DHA elicit sex-dependent effects on neonatal bone, with minimal impact on mothers.

Bone mineral changes during pregnancy and lactation

OBJECTIVE

Significant calcium transfer from the mother to the fetus and infant occurs during pregnancy and lactation, theoretically placing the mother at an increased risk for osteoporosis. The relationship between pregnancy, breast-feeding and low bone mass is controversial. In this study we aimed to elucidate the relationship between pregnancy, breast-feeding and bone mass in third trimester pregnants, at least 3 months lactating mothers, and healthy young nulliporous women by using quantitative ultrasonometry.

METHOD

The study included 120 women divided in three groups: third trimester pregnants, at least 3 months lactating mothers and healthy young nulliporous women. Demographics, total lactation time, number of pregnancies, births and miscarriages-abortions were recorded. Study groups underwent quantitative ultrasonometry measurement at midtibial shaft. Values of the ultrasonometry variables were calculated and compared for groups.

RESULTS

There were no significant differences among the groups with respect to parameters of age, age at menarche, smoking, alcohol intake and physical exercise in all of the three groups (p > 0.05). No differences were found among the three groups in analyzed variables, when comparing SOS, T- and Z-scores mid-tibial shaft quantitative ultrasonometry.

CONCLUSION

No statistically significant associations were found between ultrasonometry variables and pregnancy, breast-feeding or nulliparity.

Parathyroid and calcium metabolism disorders during pregnancy

Parathyroid disorders are not common among pregnant women, but harbor a significant morbidity and mortality potential if they remain unrecognized and untreated. The symptoms caused by abnormally low or high blood free calcium level are mostly non-specific in the initial stages, thus when recognized might pose a real danger. Here we will survey the alterations in calcium metabolism induced by pregnancy, and describe the clinical manifestations, diagnosis and treatment of parathyroid and other calcium metabolism disorders during pregnancy. The current literature on the impact of calcium and vitamin D deficiency during pregnancy will also be reviewed.

Calcium economy in human pregnancy and lactation

Pregnancy and lactation are times of additional demand for Ca. Ca is transferred across the placenta for fetal skeletal mineralisation, and supplied to the mammary gland for secretion into breast milk. In theory, these additional maternal requirements could be met through mobilisation of Ca from the skeleton, increased intestinal Ca absorption efficiency, enhanced renal Ca retention or greater dietary Ca intake. The extent to which any or all of these apply, the underpinning biological mechanisms and the possible consequences for maternal and infant bone health in the short and long term are the focus of the present review. The complexities in the methodological aspects of interpreting the literature in this area are highlighted and the inter-individual variation in the response to pregnancy and lactation is reviewed. In summary, human pregnancy and lactation are associated with changes in Ca and bone metabolism that support the transfer of Ca between mother and child. The changes generally appear to be independent of maternal Ca supply in populations where Ca intakes are close to current recommendations. Evidence suggests that the processes are physiological in humans and that they provide sufficient Ca for fetal growth and breast-milk production, without relying on an increase in dietary Ca intake or compromising long-term maternal bone health. Further research is needed to determine the limitations of the maternal response to the Ca demands of pregnancy and lactation, especially among mothers with marginal and low dietary Ca intake, and to define vitamin D adequacy for reproductive women.

Role of calcium during pregnancy: maternal and fetal needs

Although the demand for additional calcium during pregnancy is recognized, the dietary reference intake for calcium was lowered for pregnant women in 1997 to amounts recommended for nonpregnant women (1,000 mg/day), and recently (November 2010) the Institute of Medicine report upheld the 1997 recommendation. It has been frequently reported that women of childbearing age do not consume the dietary reference intake for calcium and that calcium intake in the United States varies among ethnic groups. Women who chronically consume suboptimal amounts of calcium (<500 mg/day) may be at risk for increased bone loss during pregnancy. Women who begin pregnancy with adequate intake may not need additional calcium, but women with suboptimal intakes (<500 mg) may need additional amounts to meet both maternal and fetal bone requirements. The objective of this review is to elucidate the changes in calcium metabolism that occur during pregnancy as well as the effect of maternal calcium intake on both maternal and fetal outcomes.

Amelioration of pregnancy-associated osteoporosis after treatment with vitamin K₂: a report of four patients

Abstract We demonstrate for the first time therapeutic effects of vitamin K₂ (menatetrenone) on pregnancy-associated osteoporosis with multiple vertebral fractures in four cases. Due to its safety, vitamin K₂ presents itself as a treatment option for women with pregnancy-associated osteoporosis. Desirably, future controlled studies should verify these findings.

Changes in bone mineral density and body composition during pregnancy and postpartum. A controlled cohort study

In a controlled cohort study, bone mineral density (BMD) was measured in 153 women pre-pregnancy; during pregnancy; and 0.5, 4, 9, and 19 months postpartum. Seventy-five age-matched controls, without pregnancy plans, were followed in parallel. Pregnancy and breastfeeding cause a reversible bone loss, which, initially, is most pronounced at trabecular sites but also involves cortical sites during prolonged breastfeeding.

INTRODUCTION

Conflicting results have been reported on effects of pregnancy and breastfeeding on BMD and body composition (BC). In a controlled cohort study, we elucidate changes in BMD and BC during and following a pregnancy.

METHODS

We measured BMD and BC in 153 women planning pregnancy (n = 92 conceived), once in each trimester during pregnancy and 15, 129, and 280 days postpartum. Moreover, BMD was measured 19 months postpartum (n = 31). Seventy-five age-matched controls, without pregnancy plans, were followed in parallel.

RESULTS

Compared with controls, BMD decreased significantly during pregnancy by 1.8 ± 0.5% at the lumbar spine, 3.2 ± 0.5% at the total hip, 2.4 ± 0.3% at the whole body, and 4.2 ± 0.7% at the ultra distal forearm. Postpartum, BMD decreased further with an effect of breastfeeding. At 9 months postpartum, women who had breastfed for <9 months had a BMD similar to that of the controls, whereas BMD at the lumbar spine and hip was decreased in women who were still breastfeeding. During prolonged breastfeeding, BMD at sites which consist of mostly trabecular bone started to be regained, whereas BMD at sites rich in cortical bone decreased further. At 19 months postpartum, BMD did not differ from baseline at any site. During pregnancy, fat- and lean-tissue mass increased by 19 ± 22% and 5 ± 6% (p < 0.001), respectively. Postpartum, changes in fat mass differed according to breastfeeding status with a slower decline in women who continued breastfeeding. Calcium and vitamin D intake was not associated with BMD changes.

CONCLUSION

Pregnancy and breastfeeding cause a reversible bone loss. At 19 months postpartum, BMD has returned to pre-pregnancy level independently of breastfeeding length. Reversal of changes in fat mass depends on breastfeeding status.

Breastfeeding protects against hip fracture in postmenopausal women: the Tromsø study

Despite reported bone loss during pregnancy and lactation, no study has shown deleterious long-term effects of parity or breastfeeding. Studies have shown higher bone mineral density and reduced risk for fracture in parous than in nulliparous women or no effect of parity and breastfeeding, so long-term effects are uncertain. We studied the effect of parity and breastfeeding on risk for hip, wrist and non-vertebral fragility fractures (hip, wrist, or proximal humerus) in 4681 postmenopausal women aged 50 to 94 years in the Tromsø Study from 1994-95 to 2010, using Cox's proportional hazard models. During 51 906 person-years, and a median of 14.5 years follow-up, 442, 621, and 1105 of 4681 women suffered incident hip, wrist, and fragility fractures, and the fracture rates were 7.8, 11.4, and 21.3 per 1000 person-years, respectively. The risk for hip, wrist, and fragility fracture did not differ between parous (n = 4230, 90.4%) and nulliparous women (n = 451, 9.6%). Compared with women who did not breast-feed after birth (n = 184, 4.9%), those who breastfed (n = 3564, 95.1%) had 50% lower risk for hip fracture (HR 0.50; 95% CI 0.32 to 0.78), and 27% lower risk for fragility fracture (HR 0.73; 95% CI 0.54 to 0.99), but similar risk for wrist fracture, after adjustment for age, BMI, height, physical activity, smoking, a history of diabetes, previous fracture of hip or wrist, use of hormone replacement therapy, and length of education. Each 10 months longer total duration of breastfeeding reduced the age-adjusted risk for hip fracture by 12% (HR 0.88; 95% CI 0.78 to 0.99, p for trend = 0.03) before, and marginally after, adjustment for BMI and other covariates (HR 0.91; 95% CI 0.80 to 1.04). In conclusion, this data indicates that pregnancy and breastfeeding has no long-term deleterious effect on bone fragility and fractures, and that breastfeeding may contribute to a reduced risk for hip fracture after menopause.

Calcium and bone metabolism disorders during pregnancy and lactation

Pregnancy and lactation cause a substantial increase in demand for calcium that is met by different maternal adaptations within each period. Intestinal calcium absorption more than doubles during pregnancy, whereas the maternal skeleton resorbs to provide most of the calcium content of breast milk during lactation. These maternal adaptations also affect the presentation, diagnosis, and management of disorders of calcium and bone metabolism. Although some women may experience fragility fractures as a consequence of pregnancy or lactation, for most women, parity and lactation do not affect the long-term risks of low bone density, osteoporosis, or fracture.

Antepartum bed rest for pregnancy complications: efficacy and safety for preventing preterm birth

Preterm birth is the major maternal-child health issue across developed nations and the leading cause of perinatal mortality and morbidity. Of all deaths of infants <1 year of age in the United States in 2005, 68.6% occurred in infants born prior to term. Although the preterm birth rate in European countries is 5-7%, the U.S. preterm birth rate is 12.7%, representing an increase of 9% since 2000. Antepartum bed rest/activity restriction (ABR/AR) has been a mainstay of treatment to prevent preterm birth for the past 30 years prescribed for nearly 1 million women in the United States annually, despite a lack of evidence for its effectiveness. In fact, there is increasing evidence that ABR causes several adverse physiologic and psychological side effects among women and their infants. Unfortunately, these findings have had little impact on clinical practice. This integrative review of literature provides a comprehensive analysis of the evidence for the practice of prescribing ABR and its physiologic, behavioral, and experiential side effects. It also presents a model to guide continuing research about the effects of maternal bed rest as well as evidence supporting the use of home care with bed rest, a different, safe, and feasible model of prenatal care for treating women with pregnancy complications used particularly in other countries. Finally, suggestions to improve the health of high-risk pregnant and postpartum women and their infants are provided.

Bone mineral density changes in pregnancies with gestational hypertension: a longitudinal study using quantitative ultrasound measurements

OBJECTIVE

To compare the maternal bone mineral density (BMD) changes in gestational hypertensive and normotensive pregnancies using quantitative ultrasound.

METHODS

Consecutive patients were recruited from a general obstetric clinic over a period of 9 months. BMD measurements were performed at the os calcis in early pregnancy before 20 weeks and in the late third trimester after 36 weeks, using a Hologic Sahara Clinical Bone Sonometer system. These patients were followed up in accordance with standard antenatal protocol. The diagnosis of gestational hypertension (GH) was made based on a standard institutional protocol. The changes in BMD from early to late pregnancy were compared between those with/without GH.

RESULTS

A total of 450 patients with complete data were analyzed. The overall incidence of GH was 4.8% (n = 22), of which 1.7% (n = 8) fulfilled the definitions of severe pre-eclampsia. A mean BMD loss of 0.0382 g/cm2 (around 6% of early pregnancy BMD) [corrected] was demonstrable from early to late gestation The hypertensive group has marginally higher mean BMD loss as compared to the normotensive group (0.052 vs. 0.037 g/cm²; P = 0.037). However, regression analysis models showed that early pregnancy BMD values, early pregnancy fat percentage and fat accumulation in pregnancy were significant factors affecting BMD loss during pregnancy, while GH was not in the equations.

CONCLUSION

The development of gestational hypertensive disorders apparently does not have any significant impact on BMD changes during pregnancy.

Percutaneous vertebroplasty for pregnancy-associated osteoporotic vertebral compression fractures

Osteoporosis is a worldwide problem and it mainly affects postmenopausal women. Osteoporosis associated with pregnancy or lactation is a rare condition. The incidence and mechanism of this phenomenon has not been clarified, but it can cause one or more vertebral compression fractures with severe, prolonged back pain in the affected women. We experienced this uncommon case, treated it with percutaneous vertebroplasty. A 35-old-woman visited our hospital with complaints of severe back pain and flank pain 2 months after normal vaginal delivery. She was diagnosed with osteoporotic vertebral compression fractures on the T5, 8, 9 and 11 vertebral bodies and we performed percutaneous vertebroplasty on the T8, 9 and 11 vertebrae with a good result. We present here an unusual case of pregnancy-associated compression fractures treated by percutaneous vertebroplasty.

Postpartum bone status in teenage mothers assessed using peripheral quantitative computed tomography

Teenage pregnancy occurs during a time when the maternal skeleton may still be accruing mineral. We hypothesized that teenage mothers would have reduced amounts of bone mineral and altered bone geometry compared with controls. This cross-sectional, observational compared teenage mothers (n=18) to age- and ethnicity-matched controls (n=52). The main outcomes were peripheral quantitative computed tomography and dual-energy X-ray absorptiometry to measure bone geometry, bone mineral density (BMD) at radius, lumbar spine and hip, and whole body bone mineral content (WBBMC). In teenage mothers, cortical BMD was reduced at the radial diaphysis (mean difference: -1.3%; p=0.03). Size-adjusted WBBMC was reduced (mean difference: -4.0%; p=0.004) and was lower for a given amount of lean mass (mean difference: -5.8%; p=0.02). No other significant differences between groups were found. The recruitment and retention of participants to this study were extremely difficult and disappointing. Teenage mothers had lower BMD at cortical sites compared with age-matched controls. These data suggest that pregnancy might have a detrimental effect on teenage mothers' future skeletal health. The results of this study require confirmation and provide pilot data for further investigations.

Effect of parity on phalangeal bone mineral density in post-menopausal Sri Lankan women: a community based cross-sectional study

There is paucity of studies related to parity and bone mineral density in South Asian countries. We recruited 713 healthy, community dwelling post-menopausal women from seven provinces in Sri Lanka for this survey. The number of pregnancies, including miscarriages beyond 20 weeks of gestation, was recorded. Women with diseases and those who have taken drugs that can affect bone mineral density (BMD) were excluded (n = 15). Phalangeal BMD and bone mineral content (BMC) were measured using AccuDEXA in 713 women. Mean (SE) BMD of nulliparous women (n = 32), women with one to two pregnancies (n = 284), three to four pregnancies (n = 290) and more than four pregnancies (n = 107) were 0.437(0.014), 0.454(0.005), 0.455(0.005) and 0.417(0.006) g/cm(2), respectively (P < 0.001). Corresponding mean (SE) BMCs were 1.30(0.063), 1.41(0.021), 1.43(0.022) and 1.32(0.033) g, respectively (P < 0.001). Women with more than four pregnancies were older and lighter when compared with other groups. When results were adjusted for current age and current weight, differences in mean BMD and BMC between groups became non-significant. BMD of nulliparous women remained low in all analyses. We report a significant difference in unadjusted phalangeal BMD in women categorized according to their parity. Women with one to four pregnancies had the highest phalangeal BMD and BMC, while multi-parous (more than four pregnancies) and nulliparous women had lower values. However, in an adjusted analysis, the differences in BMD and BMC were partially explained by the differences of age and body weight between the groups and the unique effect of parity was difficult to determine. Women with lower BMD may have a higher risk of future fractures.

Bone mineral density changes in gestational diabetic pregnancies-a longitudinal study using quantitative ultrasound measurements of the os calcis

To compare the maternal bone mineral density (BMD) changes in gestational diabetic and non-diabetic pregnancies using quantitative ultrasound measurements of the os calcis, BMD measurements were performed at the os calcis in early pregnancy before 20 weeks and in the late third trimester after 36 weeks, using a Hologic Sahara Clinical Bone Sonometer system. Random glucose screening and direct oral glucose tolerance testing were used to diagnose gestational diabetes mellitus (GDM) according to World Health Organization criteria, which was then treated according to a standard protocol. In a cohort of 480 patients, there were 96 gestational diabetic patients (14 GDM and 82 with impaired glucose tolerance). The mean BMD loss was higher in diabetic patients compared with controls (0.038 vs. 0.025 g/cm2, p = 0.048). A regression model of all pregnancies showed that higher fat accumulation was related to lower BMD loss, but diabetic status was not in the equation. Within diabetic pregnancies, lower initial BMD values, higher fat accumulation and higher early-pregnancy body mass index were associated with lower BMD loss. While gestational diabetic women had higher BMD loss than non-diabetic women, this was apparently secondary to other anthropometric factors rather than due directly to the gestational diabetic state.

Kyphoplasty for pregnancy-associated osteoporotic vertebral fractures

We report a case of pregnancy-associated osteoporotic vertebral fracture treated by kyphoplasty. This case is important for being the first case of postpregnancy osteoporotic vertebral fracture treated with kyphoplasty. Although kyphoplasty is a very successful procedure in short-term pain relief for osteoporotic vertebral fractures, there is a critical need for randomized controlled trials demonstrating short-term complications of kyphoplasty including new vertebral fractures.

Bone status during adolescence, pregnancy and lactation

PURPOSE OF REVIEW

At birth, the fetus will contain 30 g of calcium; during the third trimester the calcium accrual can be up to 340 mg/day. Therefore, extremely high demands for calcium provision are placed upon the mother. This review aims to describe the adaptive mechanisms of the female skeleton to pregnancy and lactation, which ensure optimal fetal skeletal mineralization without compromise to maternal bone strength.

RECENT FINDINGS

Descriptions of changes in bone status during pregnancy and lactation have been published. One of the only studies to measure pre-conception to post-weaning shows complete recovery of maternal spinal bone mineral density (BMD) and near recovery at the hip. Most studies describe trabecular bone loss, but there is evidence for endosteal resorption of the metacarpals. In a retrospective study of former teenage mothers those who breastfed had similar hip BMD to nulliparous age-matched women; those who did not breastfeed had lower hip BMD. Maternal response to low calcium intake differs from that of normal calcium intake.

SUMMARY

Pregnancy and lactation do not have an overall negative effect upon the maternal skeleton. Retrospective evidence suggests no harmful effect of teenage pregnancy if the teenager breastfed, but this requires further investigation. The effects of other situations, for example low vitamin D status or low calcium intake, require further research to inform future clinical practice.

Calcium and bone metabolism during pregnancy and lactation

Pregnancy and lactation both place significant demands on the mother to provide sufficient calcium (among other minerals and nutrients) to the fetus and neonate. Despite facing similar demands for calcium during pregnancy and lactation, the maternal adaptations differ significantly between these two reproductive periods. Women lose 300 to 400 mg of calcium daily through breast milk, and this calcium demand is met by a 5-10% loss of skeletal mineral content during 6 months of exclusive lactation. Most importantly, the lost mineral is fully restored within a few months of weaning, such that women who have breastfed do not have a long-term deficit in skeletal mineral content. This article will review our present understanding of the adaptations in mineral metabolism that occur during pregnancy and lactation, and will focus on recent evidence that the breast itself plays a central role in regulating the adaptations during lactation.

Effects of pregnancy and lactation on bone mineral density, and their relation to the serum calcium, phosphorus, calcitonin and parathyroid hormone levels in rats

The aim of this study was to evaluate the net changes in bone mineral density (BMD) during the reproductive cycle, and their relation with changes in serum calcium (Ca), phosphorus (P), PTH and calcitonin levels in rats. Twenty-seven female Wistar rats were included in this study. They were divided into three groups as pregnant, lactating and control groups. BMDs of lumbar vertebrates, femoral and tibial bones, and Ca, P, calcitonin and PTH levels were measured at the end of pregnancy, at the end of lactation and in nulliparous controls. In the pregnant group, the BMDs of rats were significantly higher in lumbar vertebrates, femoral and tibia bones than those of the control group (p<0.05). Their PTH and Ca levels were significantly lower than the control group (p<0.05). However, no statistically significant difference was found regarding P and calcitonin levels when compared to those of the control group. In the lactating group, the BMDs were significantly lower in lumbar vertebrates, femoral and tibia bones than those seen in the control and pregnant groups (p<0.05). Ca and PTH levels were significantly higher in lactating rats than in those of pregnant rats (p<0.005). Normal pregnancy increases BMD in rats, whereas lactation decreases it. Change in PTH levels is supposed to contribute to the mineralization and demineralization of the skeleton during pregnancy and lactation, respectively.

Determinants of peak bone mineral density and bone area in young women

Osteoporosis is a disease caused by compromised bone strength, and individuals with a high peak bone mass at a young age are likely to have a high bone mass in old age. To identify the clinical determinants of peak bone mass in young adult women, 418 southern Chinese women, aged 20-39 years, were studied. Low bone mass was defined as areal bone mineral density (aBMD) Z-score < -1 at either the spine or total hip. Within the cohort, 62 (19.0%) and 86 (26.4%) women had low aBMD at the spine and hip, respectively. Regression model analysis revealed that low body weight (<44 kg) was associated with an 8.3-fold (95% CI, 3.7-18.9) and a 6.8-fold (95% CI, 3.0-15.6) risk of having low aBMD at the spine and hip, respectively. Low body weight was also predictive of low volumetric BMD (vBMD) at the spine (odds ratio (OR) 7.8, 95% CI, 3.1-20.1) and femoral neck (OR 3.0, 95% CI, 1.3-7.1). A body height below 153 cm was associated with a 4.8-fold risk in the small L2-4 bone area (95% CI, 2.3-9.8) and a 3.9-fold risk in the small femoral neck area (95% CI, 1.9-8.1). Delayed puberty (onset of menstruation beyond 14 years) was associated with a 2.2-fold (95% CI, 1.0-4.9) increased risk of having low aBMD at the hip. Physical inactivity was associated with a 2.8-fold risk of low spine vBMD (OR 2.8, 95% CI, 1.1-6.7) and a 3.3-fold risk of low hip aBMD (95% CI, 1.0-10.0). Pregnancy protected against low spine aBMD (OR 0.4, 95% CI, 0.1-1.2) and spine vBMD (OR 0.1, 95% CI, 0.0-1.0), low femoral neck vBMD (OR 0.3, 95% CI, 0.1-1.1) and small L2-4 bone area vBMD (OR 0.3, 95% CI, 0.1-1.1). In conclusion, this study identified a number of modifiable determinants of low peak bone mass in young adult women. Maintaining an ideal body weight, engaging in an active lifestyle, and diagnosing late menarche may enable young women to maximize their peak bone mass and so reduce their risk of osteoporosis in later life.

Bed rest and other determinants of bone loss during pregnancy

OBJECTIVE

The purpose of this study was to evaluate patterns of bone loss during pregnancy and potential influences.

STUDY DESIGN

This was a prospective study of 181 women receiving prenatal care at Magee-Womens Hospital or its auxiliary clinics in Pittsburgh, Pennsylvania, between 1992 and 1995. Bone mineral density was measured at approximately 16 and 36 weeks' gestation.

RESULTS

Trabecular, but not cortical, bone loss occurred during pregnancy. Mean ultra-distal bone mineral density loss was 1.9% (95% CI 1.2-2.5) during the 20-week period. Women prescribed bed rest had an adjusted mean loss of 4.6% compared with 1.5% for women not prescribed bed rest ( P = .001) and 6-fold higher odds ( P = .001) of bone loss > or =5% during the 20-week period. Nulliparity, calcium intake < 2 000 mg/day, low weight gain, and maternal age < 21 or >30 years were more modestly associated with greater bone loss.

CONCLUSION

Substantial trabecular bone loss may occur during pregnancy, particularly in women prescribed bed rest. Study of postpartum bone recovery in such women is needed.