Changes in bone mineral status and bone size during pregnancy and the influences of body weight and calcium intake

Current Evidence about Developmental Dysplasia of the Hip in Pregnancy

In adults, developmental dysplasia of the hip (DDH) represents a spectrum of disorders. It is commonly found in women in routine orthopedic practice. Hip dysplasia is a leading precursor of joint laxity; when untreated, it can contribute to chronic modifications, such as thickening of the pulvinar and ligamentum teres (which can also elongate), hypertrophy of the transverse acetabular ligament, and osteoarthritis. DDH is presumed to be associated with alterations in pelvic morphology that may affect vaginal birth by the reduction in the transverse diameter of the pelvic inlet or outlet. Here, we provide an overview of the current knowledge of pregnancy-associated DDH. We primarily focused on how a surgical DDH treatment might influence the pelvic shape and size and the effects on the mechanism of birth. We presented the female pelvis from the standpoint of bone and ligament morphology relative to a pelvic osteotomy. Then, we described whether the pregnancy was impacted by previous surgical DDH treatments, performed from infancy to adulthood. In conclusion, hip dysplasia is not associated with high-risk complications during pregnancy or with increased difficulty in vaginal delivery.

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.

Global inequities in dietary calcium intake during pregnancy: a systematic review and meta-analysis

BACKGROUND

Evidence shows that adequate calcium intake during pregnancy reduces the risk of hypertensive disorders of pregnancy. In most low- and middle-income countries (LMICs) the daily calcium intake is well below recommendations. Mapping calcium intake during pregnancy worldwide and identifying populations with low calcium intake will provide the evidence base for more targeted actions to improve calcium intake.

OBJECTIVE

To assess dietary calcium intake during pregnancy worldwide.

SEARCH STRATEGY

MEDLINE and EMBASE (from July 2004 to November 2017).

SELECTION CRITERIA

Cross-sectional, cohort, and intervention studies reporting calcium intake during pregnancy.

DATA COLLECTION AND ANALYSIS

Five reviewers working in pairs independently performed screening, extraction, and quality assessment. We reported summary measures of calcium intake and calculated the weighted arithmetic mean for high-income countries (HICs) and LMICs independently, and for geographic regions, among studies reporting country of recruitment, mean intake, and total number of participants. When available, inadequate intakes were reported.

MAIN RESULTS

From 1880 citations 105 works met the inclusion criteria, providing data for 73 958 women in 37 countries. The mean calcium intake was 948.3 mg/day (95% CI 872.1-1024.4 mg/day) for HICs and 647.6 mg/day (95% CI 568.7-726.5 mg/day) for LMICs. Calcium intakes below 800 mg/day were reported in five (29%) countries from HICs and in 14 (82%) countries from LMICs.

CONCLUSION

These results are consistent with a lack of improvement in calcium dietary intake during pregnancy and confirm the gap between HICs and LMICs, with alarmingly low intakes recorded for pregnant women in LMICs. From the public health perspective, in the absence of specific local data, calcium supplementation of pregnant women in these countries should be universal.

TWEETABLE ABSTRACT

Despite dietary recommendations, women in LMICs face pregnancy with diets low in calcium.

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.

Calcium intake in winter pregnancy attenuates impact of vitamin D inadequacy on urine NTX, a marker of bone resorption

PURPOSE

Pregnancy is characterised by increased bone turnover, but high bone turnover with resorption exceeding formation may lead to negative maternal bone remodelling. Recent studies are conflicting regarding the effect of calcium on skeletal health in pregnancy. The aim of this study was to examine the seasonal effect of serum 25-hydroxyvitamin D (25OHD) and dietary calcium on a marker of bone resorption.

METHODS

This was prospective study of 205 pregnant women [two cohorts; early pregnancy at 13 weeks (n = 96), and late pregnancy at 28 weeks (n = 109)]. Serum 25OHD and urine cross-linked N-telopeptides of type I collagen (uNTX) were measured at both time points. Intakes of vitamin D and calcium were recorded using 3-day food diaries at each trimester.

RESULTS

Compared to summer pregnancies, winter pregnancies had significantly lower 25OHD and significantly higher uNTX. Higher calcium intakes were negatively correlated with uNTX in winter, but not summer. In late pregnancy, compared to those reporting calcium intakes ≥1000 mg/day, intakes of <1000 mg/day were associated with a greater increase in uNTX in winter pregnancies than in summer (41.8 vs. 0.9%). Increasing calcium intake in winter by 200 mg/day predicted a 13.3% reduction in late pregnancy uNTX.

CONCLUSIONS

In late pregnancy, during winter months when 25OHD is inadequate, intakes of dietary calcium <1000 mg/day were associated with significantly increased bone resorption (uNTX). Additional dietary calcium is associated with reduced bone resorption in late pregnancy, with greater effect observed in winter. Further research regarding optimal dietary calcium and 25OHD in pregnancy is required, particularly for women gestating through winter.

The Pattern of Gestational Weight Gain is Associated with Changes in Maternal Body Composition and Neonatal Size

OBJECTIVES

The pattern of gestational weight gain (GWG) reflects general nutrient availability to support growing fetal and maternal compartments and may contribute to later health, but how it relates to changes in maternal body composition is unknown. We evaluated how the pattern of GWG related to changes in maternal body composition during pregnancy and infant size at birth.

METHODS

A prospective, multi-ethnic cohort of 156 pregnant women and their infants was studied in New York City. Prenatal weights were used to estimate total and rate (kg/week) of GWG by trimester. Linear regression models evaluated the association between trimester-specific GWG group (low, medium, high GWG) [total (low ≤25, high ≥75 percentile) or rate (defined by tertiles)] and infant weight, length and maternal body composition changes from 14 to 37 weeks, adjusting for covariates.

RESULTS

Compared to the low gain group, medium/high rate of GWG in the second trimester and high rate of GWG in the third trimester were associated with larger gains in maternal fat mass (β range for fat Δ = 2.86-5.29 kg, all p < 0.01). For infant outcomes, high rate of GWG in the second trimester was associated with higher birth weight (β = 356 g, p = 0.001) and length (β = 0.85 cm, p = 0.002). First and third trimester GWG were not associated with neonatal size.

CONCLUSIONS

The trimester specific pattern and rate of GWG reflect changes in maternal body fat and body water, and are associated with neonatal size, which supports the importance of monitoring trimester-specific GWG.

Low mineral density of a weight-bearing bone among adult women in a high fertility population

Evolutionary theories of aging posit that greater reproductive effort causes somatic decline given a fundamental trade-off between investing energy in reproduction and repair. Few studies in high fertility human populations support this hypothesis, and problems of phenotypic correlation can obscure the expected trade-off between reproduction and somatic condition. This cross-sectional study investigates whether greater reproductive effort is associated with reduced calcaneal bone mineral density (BMD) among female Tsimane forager-farmers of lowland Bolivia. We also investigate whether female Tsimane BMD values are lower than sex- and age-matched US reference values, despite the fact that Tsimane engage in higher physical activity levels that can increase mechanical loading. To measure calcaneal BMD, quantitative ultrasonography was performed on 130 women (mean ± SD age = 36.6 ± 15.7, range = 15-75) that were recruited regardless of past or current reproductive status. Anthropometric and demographic data were collected during routine medical exams. As predicted, higher parity, short inter-birth interval, and earlier age at first birth are associated with reduced BMD among Tsimane women after adjusting for potential confounders. Population-level differences are apparent prior to the onset of reproduction, and age-related decline in BMD is greater among Tsimane compared with American women. Greater cumulative reproductive burden may lower calcaneal BMD individually and jointly with other lifestyle and heritable factors. Fitness impacts of kin transfers in adulthood may determine the value of investments in bone remodeling, and thus affect selection on age-profiles of bone mineral loss.

Body composition changes in pregnancy: measurement, predictors and outcomes

Prevalence of overweight and obesity has risen in the United States over the past few decades. Concurrent with this rise in obesity has been an increase in pregravid body mass index and gestational weight gain affecting maternal body composition changes in pregnancy. During pregnancy, many of the assumptions inherent in body composition estimation are violated, particularly the hydration of fat-free mass, and available methods are unable to disentangle maternal composition from fetus and supporting tissues; therefore, estimates of maternal body composition during pregnancy are prone to error. Here we review commonly used and available methods for assessing body composition changes in pregnancy, including: (1) anthropometry, (2) total body water, (3) densitometry, (4) imaging, (5) dual-energy X-ray absorptiometry, (6) bioelectrical impedance and (7) ultrasound. Several of these methods can measure regional changes in adipose tissue; however, most of these methods provide only whole-body estimates of fat and fat-free mass. Consideration is given to factors that may influence changes in maternal body composition, as well as long-term maternal and offspring outcomes. Finally, we provide recommendations for future research in this area.

Vitamin D, folate, and potential early lifecycle environmental origin of significant adult phenotypes

Solar radiation early in pregnancy interacts with light sensitive vitamins to influence an embryo's genetic profile. This influences both adult disease risk and may play a role in the evolution of skin colour.

Background and objectives: Vitamin D and folate are highly UV sensitive, and critical for maintaining health throughout the lifecycle. This study examines whether solar irradiance during the first trimester of pregnancy influences vitamin D receptor (VDR) and nuclear folate gene variant occurrence, and whether affected genes influence late-life biochemical/clinical phenotypes.

Methodology: 228 subjects were examined for periconceptional exposure to solar irradiance, variation in vitamin D/folate genes (polymerase chain reaction (PCR)), dietary intake (food frequency questionnaire (FFQ)) and important adult biochemical/clinical phenotypes.

Results: Periconceptional solar irradiance was associated with VDR-BsmI (P = 0.0008^wk7), TaqI (P = 0.0014^wk7) and EcoRV (P = 0.0030^wk6) variant occurrence between post-conceptional weeks 6–8, a period when ossification begins. Similar effects were detected for other VDR gene polymorphisms. Periconceptional solar irradiance was also associated with 19 bp del-DHFR (P = 0.0025^wk6), and to a lesser extent C1420T-SHMT (P = 0.0249^wk6), a folate-critical time during embryogenesis. These same genes were associated with several late-life phenotypes: VDR-BsmI, TaqI and ApaI determined the relationship between dietary vitamin D and both insulin (P < 0.0001/BB, 0.0007/tt and 0.0173/AA, respectively) and systolic blood pressure (P = 0.0290/Bb, 0.0299/Tt and 0.0412/AA, respectively), making them important early and late in the lifecycle. While these and other phenotype associations were found for the VDR variants, folate polymorphism associations in later-life were limited to C1420T-SHMT (P = 0.0037 and 0.0297 for fasting blood glucose and HbA1c levels, respectively). We additionally report nutrient–gene relationships with body mass index, thiol/folate metabolome, cognition, depression and hypertension. Furthermore, photoperiod at conception influenced occurrence of VDR-Tru9I and 2R3R-TS genotypes (P = 0.0120 and 0.0360, respectively).

Conclusions and implications: Findings identify environmental and nutritional agents that may interact to modify gene–phenotype relationships across the lifecycle, offering new insight into human ecology. This includes factors related to both disease aetiology and the evolution of skin pigmentation.

Bone mineral changes after lactation in Gambian women accustomed to a low calcium intake

BACKGROUND/OBJECTIVES

Previous studies in Gambian women with a low calcium intake have described decreases in whole-body and regional bone mineral content (BMC) and areal bone mineral density (aBMD) during the first year of lactation. The aim of this study was to examine whether these effects are reversed after lactation.

SUBJECTS/METHODS

Thirty-three Gambian women who had a previous dual-energy X-ray absorptiometry (DXA) scan at 52 weeks lactation (L52) were invited to participate in a follow-up study when neither pregnant nor lactating (NPNL) for ≥3 months and/or when 52 weeks postpartum in a subsequent lactation (F52). Whole body, lumbar spine and hip bone mineral were measured by DXA. Anthropometry and dietary assessments were also conducted. Repeated-measures analysis of covariance was used to determine differences from L52 at NPNL and F52.

RESULTS

Twenty-eight women were scanned at NPNL and 20 at F52. The mean±s.d. calcium intake of the 33 women at NPNL and F52 was 360±168 mg/day. BMC, aBMD and size-adjusted BMC (SA-BMC) at all sites were higher at NPNL than L52. Percent increases in SA-BMC (mean±s.e.m.) were significant (P<0.0001): whole body=2.7±0.4%; lumbar spine=4.9±1.0%; total hip=3.7±1.0%. There were no significant differences in any measurements between the two lactation time points (L52 and F52).

CONCLUSIONS

This study of Gambian women with low calcium intakes demonstrates that bone mineral mobilised during lactation is recovered after lactation. Successive periods of long lactation are not associated with progressive skeletal depletion.

Unexpected long-term effects of calcium supplementation in pregnancy on maternal bone outcomes in women with a low calcium intake: a follow-up study

BACKGROUND

Calcium supplementation of pregnant Gambian women with a low calcium intake results in lower maternal bone mineral content in the subsequent lactation.

OBJECTIVE

The objective was to investigate whether the lower bone mineral content persists long term.

DESIGN

All women in the calcium supplementation trial (International Trial Registry ISRCTN96502494) who had been scanned with dual-energy X-ray absorptiometry at 52 wk of lactation (L52; n = 79) were invited for follow-up when neither pregnant nor lactating for ≥3 mo (NPNL) or at 52 wk postpartum in a future lactation (F52). Bone scans and anthropometric and dietary assessments were conducted.

RESULTS

Sixty-eight women participated (35 at both NPNL and F52 and 33 at only one time point): n = 59 NPNL (n = 31 calcium, n = 28 placebo) and n = 44 F52 (n = 24 calcium, n = 20 placebo). The mean (±SD) time from L52 was 4.9 ± 1.9 y for NPNL and 5.0 ± 1.3 y for F52. Size-adjusted bone mineral content (SA-BMC) was greater at NPNL than at L52 in the placebo group (P ≤ 0.001) but not in the calcium group (P for time-by-group interaction: lumbar spine, 0.002; total hip, 0.03; whole body, 0.03). No significant changes in SA-BMC from L52 to F52 were observed in either group. Consequently, the lower SA-BMC in the calcium group at L52 persisted at NPNL and F52 (P ≤ 0.001): NPNL (lumbar spine, -7.5 ± 0.7%; total hip, -10.5 ± 1.0%; whole body, -3.6 ± 0.5%) and F52 (lumbar spine, -6.2 ± 0.9%; total hip, -10.3 ± 1.4%; whole body, -3.2 ± 0.6%).

CONCLUSION

In rural Gambian women with a low-calcium diet, a calcium supplement of 1500 mg/d during pregnancy resulted in lower maternal bone mineral content in the subsequent lactation that persisted long term. This trial was registered at www/controlled-trials.com/mrct/ as ISRCTN96502494.

Acute response to oral calcium loading in pregnant and lactating women with a low calcium intake: a pilot study

This pilot study in women from The Gambia with low habitual calcium intakes showed differences in calciotropic hormones between pregnant, lactating and non-pregnant, non-lactating women similar to those in Western women. The response to oral calcium loading indicates a high degree of calcium conservation independent of reproductive status.

INTRODUCTION

In pregnancy and early lactation, parathyroid hormone (PTH) concentrations may be suppressed. Uncertainty exists about how calcium metabolism is regulated, particularly when calcium intake is low.

METHODS

We investigated fasting markers of calcium metabolism and the acute calcemic and calciuric responses after an oral calcium load in 30 pregnant, lactating or non-pregnant, non-lactating (NPNL) Gambian women with low habitual calcium intakes. Women received 1 g elemental calcium (CaCO3) at 0 min. Blood was collected at -30 and 180 min. Urine was collected from -60 to 0, 0-120 and 120-240 min. Samples were analysed (blood: ionized calcium (iCa); plasma (p): total calcium (tCa), phosphate (P), creatinine (Cr), PTH, 1,25-dihydroxyvitamin D (1,25(OH)2D), osteocalcin (OC), β C-terminal cross-linked telopeptide of type 1 collagen (βCTX), cyclic adenosine monophosphate (cAMP); urine (u): Ca, P, Cr, cAMP).

RESULTS

Pre-loading, groups did not differ significantly in iCa, pP, uCa/Cr and uP/Cr. pOC concentrations were significantly lower and NcAMP and p1,25(OH)2D higher in pregnant women; pPTH and pβCTX in lactating women were higher than in NPNL women. Post-loading, iCa, ptCa and uCa/Cr concentrations increased; pPTH, NcAMP, βCTX and uP/Cr decreased in all groups, but the magnitude of change did not differ significantly between groups.

CONCLUSION

Differences between pregnant, lactating and NPNL Gambian women in pPTH, NcAMP and p1,25(OH)2D and bone markers were similar to Western women. However, the response to calcium loading indicates that there may be no differences in renal and intestinal calcium economy associated with reproductive status, potentially due to a high degree of calcium conservation associated with low intakes.

A limp in a pregnant woman as a first presentation of celiac disease

A 25-year-old Arab woman, reported to our endocrinology clinic one month post-partum presenting with back pain and a limp that started during the seventh month of pregnancy. Upon examination, she was found to have a full range of motion and no tenderness in the hip joint or lower back. The pain was aggravated by walking. She had a limping gait with a lean to her right side. She had low calcium, low hemoglobin, high parathyroid hormone and high alkaline phosphatase levels. X-rays of her hip and lumbosacral areas were normal. Her spinal magnetic resonance imaging findings were also normal. A bone mineral density (BMD) study revealed severe osteoporosis with a lumbar spine T-score of -4.6 and femoral neck T-scores of -4.1 (left) and -3.9 (right). A celiac disease work-up included tests for anti-endomysial antibodies and anti-tissue transglutaminase antibodies, which were positive, and the results of an endoscopy and biopsy confirmed the diagnosis of celiac disease. Gluten-free diet with calcium and vitamin D supplementation resulted in the complete resolution of her symptoms and a normal gait. The patient returned to normal calcium and parathyroid hormone levels and experienced a significant improvement in her BMD to normal. Celiac disease may initially presents during pregnancy result in severe osteoporosis that causes significant pain and disability.

Proximal femur structural geometry changes during and following lactation

Human lactation is associated with transient decreases in bone mineral density (BMD). Bone strength is related to both mass and structural geometry. This study investigated longitudinal changes of hip bone strength during lactation using hip structural analysis (HSA), which determines hip structural geometry (including areal BMD, BMDa) from dual-energy X-ray absorptiometry scans (DXA). Forty-eight lactating women were studied longitudinally at the proximal femur using DXA at approximately 2 weeks postpartum, peak-lactation and post-lactation. Nonpregnant, nonlactating women (NPNL, n=23) were studied concurrently at baseline and after 1 year. Hip scans were analysed using HSA at the narrow neck, intertrochanter and proximal shaft. No significant change (>0.05) was observed in NPNL women for any measurement. In contrast, for lactating women BMDa decreased significantly from 2 weeks postpartum to peak-lactation at narrow neck (-2.8%), intertrochanter (-3.2%) and shaft (-1.4%). Cross-sectional area (CSA) decreased at narrow neck (-3.4%) and intertrochanter (-2.7%). There were no significant changes in bone width. Section modulus decreased at intertrochanter (-2.1%). At shaft, cortical thickness decreased (-1.7%) and buckling ratio increased (2.3%). By post-lactation, measurements were not significantly different from 2 weeks postpartum except for decrements in BMDa (-1.1%) and CSA (-1.2%) at the shaft. During the study, lactating women lost 5% of their body weight. Adjusting for weight changes decreased the magnitude and significance of HSA changes at peak-lactation and by post-lactation there were no significant differences from 2 weeks postpartum. Calcium intake was not a significant predictor of changes in HSA variables. In conclusion, lactation is associated with significant but transient changes in hip BMD and structural geometry. Changes in body weight but not calcium intake were associated with these changes. These small changes at the hip during lactation occurred mainly at internal surfaces and had minimal impact on bending or compressive strength.

Effect of calcium supplementation in pregnancy on maternal bone outcomes in women with a low calcium intake

BACKGROUND

Mobilization of maternal bone mineral partly supplies calcium for fetal and neonatal bone growth and development.

OBJECTIVE

We investigated whether pregnant women with low calcium intakes may have a more extensive skeletal response postpartum that may compromise their short- or long-term bone health.

DESIGN

In a subset of participants (n = 125) in a double-blind, randomized, placebo-controlled trial (International Trial Registry: ISRCTN96502494) in pregnant women in The Gambia, West Africa, with low calcium intakes (approximately 350 mg Ca/d), we measured bone mineral status of the whole body, lumbar spine, and hip by using dual-energy X-ray absorptiometry and measured bone mineral status of the forearm by using single-photon absorptiometry at 2, 13, and 52 wk lactation. We collected blood and urine from the subjects at 20 wk gestation and at 13 wk postpartum. Participants received calcium carbonate (1500 mg Ca/d) or a matching placebo from 20 wk gestation to parturition; participants did not consume supplements during lactation.

RESULTS

Women who received the calcium supplement in pregnancy had significantly lower bone mineral content (BMC), bone area (BA), and bone mineral density (BMD) at the hip throughout 12 mo lactation (mean +/- SE difference: BMC = -10.7 +/- 3.7%, P = 0.005; BA = -3.8 +/- 1.9%, P = 0.05; BMD = -6.9 +/- 2.6%, P = 0.01). The women also experienced greater decreases in bone mineral during lactation at the lumbar spine and distal radius and had biochemical changes consistent with greater bone mineral mobilization.

CONCLUSIONS

Calcium supplementation in pregnant women with low calcium intakes may disrupt metabolic adaptation and may not benefit maternal bone health. Further study is required to determine if such effects persist long term or elicit compensatory changes in bone structure.

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.

Evidence for enhanced characterization of cortical bone using novel pQCT shape software

Bone shape, mass, structural geometry, and material properties determine bone strength. This study describes novel software that uses peripheral quantitative computed tomography (pQCT) images to quantify cortical bone shape and investigates whether the combination of shape-sensitive and manufacturer's software enhances the characterization of tibiae from contrasting populations. Existing tibial pQCT scans (4% and 50% sites) from Gambian (n=38) and British (n=38) women were used. Bone mass, cross-sectional area (CSA), and geometry were determined using manufacturer's software; cross-sectional shape was quantified using shape-sensitive software. At 4% site, Gambian women had lower total bone mineral content (BMC: -15.4%), CSA (-13.4%), and trabecular bone mineral density (BMD: -19%), but higher cortical subcortical BMD (6.1%). At 50% site, Gambian women had lower cortical BMC (-7.6%), cortical CSA (-12.6%), and mean cortical thickness (-15.0%), but higher cortical BMD (4.9%) and endosteal circumference (8.0%). Shape-sensitive software supported the finding that Gambian women had larger tibial endosteal circumference (9.8%), thinner mean cortical thickness (-26.5%) but smaller periosteal circumference (-5.6%). Shape-sensitive software revealed that Gambian women had tibiae with shorter maximum width (-7.6%) and thinner cortices (-22% to -41.2%) and more closely resembled a circle or ellipse. Significant differences remained after adjusting for age, height, and weight. In conclusion, shape-sensitive software enhanced the characterization of tibiae in 2 contrasting groups of women.