Ultrasonographic bone characteristics during normal pregnancy: longitudinal and cross-sectional evaluation

A case of pregnancy and lactation associated osteoporosis in the third pregnancy; robust response to teriparatide despite delayed administration

BACKGROUND

Pregnancy and lactation associated osteoporosis (PLO) is a rare condition that may present with fragility fractures occurring for the first time in pregnancy or postpartum period while breastfeeding. Here, we report a rare case of PLO in the 3rd pregnancy treated with teriparatide.

CASE REPORT

A 35-year-old woman who presented with back pain (visual analogue scale; VAS = 10/10) two months after her third delivery. PLO was diagnosed from multiple vertebral fragility fractures and low bone mineral density (BMD). She was treated with teriparatide and her pain significantly reduced in the second month. After 12 months of teriparatide treatment, her BMD increased 18.1% from the baseline.

CONCLUSION

PLO should be considered in patients who complain with back pain during late pregnancy and postpartum period. Weaning off breastfeeding and supplementation of calcium/vitamin D should be the first recommendation as conventional treatment after the diagnosis of PLO. Teriparatide may be an effective option to improve the recovery of BMD If there is not enough improvement with conventional treatment.

Maternal vitamin D biomarkers are associated with maternal and fetal bone turnover among pregnant women consuming controlled amounts of vitamin D, calcium, and phosphorus

Vitamin D plays a central role in calcium homeostasis; however, its relationship with bone turnover during pregnancy remains unclear due to a lack of studies that have rigorously controlled for vitamin D and other nutrients known to influence bone metabolism. Similarly, prior investigations of the effect of pregnancy on bone turnover relative to the nonpregnant state may have been confounded by varying intakes of these nutrients. Nested within a controlled intake study, the present investigation sought to quantify associations between maternal vitamin D biomarkers and biochemical markers of bone turnover among pregnant (versus nonpregnant) women and their fetuses under conditions of equivalent and adequate intakes of vitamin D and related nutrients. Changes in markers of bone turnover across the third trimester were also examined. Healthy pregnant (26-29 wk gestation; n=26) and nonpregnant (n=21) women consumed 511IU vitamin D/d, 1.6g calcium/d, and 1.9g phosphorus/d for 10weeks while participating in a controlled feeding study featuring two choline doses. Based on linear mixed models adjusted for influential covariates (e.g., BMI, ethnicity, and season), pregnant women had 50-150% higher (P<0.001) concentrations of bone resorption markers than nonpregnant women. Among pregnant women, increases in maternal 25(OH)D across the study period were associated (P<0.020) with lower osteocalcin and deoxypyridinoline at study-end, and higher fetal osteocalcin. In addition, maternal free 25(OH)D, 1,25(OH)₂D and 24,25(OH)₂D tended to be negatively associated (P≤0.063) with maternal NTx at study-end, and maternal free 25(OH)D and 24,25(OH)₂D were positively associated (P≤0.021) with fetal CTx. Similarly, maternal 3-epi-25(OH)D₃ was negatively related (P≤0.037) to maternal NTx and deoxypyridinoline at study-end. These declines in bone resorption markers resulting from higher vitamin D biomarker concentrations among pregnant women coincided with increases in their albumin-corrected serum calcium concentrations, indicating that calcium transfer to the fetus was uncompromised. Notably, none of these associations achieved statistical significance among nonpregnant women. Overall, our study findings suggest that achieving higher maternal concentrations of vitamin D biomarkers might attenuate third-trimester bone resorption while ensuring sufficient calcium delivery to the fetus.

Feto-maternal Bone Remodeling in Normal Pregnancy and Preeclampsia

OBJECTIVES

To investigate feto-maternal bone turnover in normal pregnancy and preeclampsia and to test the hypothesis whether the reported low bone mass at birth in small-for-gestational age infants is associated with decreased bone formation or increased bone resorption.

METHODS

Thirty-two patients with preeclampsia (17 mild and 15 severe) and 20 normotensive women (controls) with singleton gestations in the third trimester participated in this study. Furthermore, 25 nonpregnant healthy women were chosen as nonpregnant controls. Maternal 24-hour urine specimens and venous blood samples were collected. In addition, fetal cord blood and the first voided neonatal urine were also collected. The freshly separated sera were assayed for osteocalcin (OC) and carboxy-terminal propeptide of type 1 collagen (PICP) by radioimmunoassay. Urine samples were assayed for N-telopeptide of type 1 collagen (NTx) by enzyme-linked immunosorbent assay.

RESULTS

Maternal and cord serum OC and PICP levels were significantly decreased in severe preeclampsia, whereas maternal and first-voided neonatal urinary NTx level were significantly increased compared to the corresponding levels of controls. In both mother and fetus, the coupling index of markers of bone turnover in normal pregnancy or mild preeclampsia was in favor of bone formation, whereas in severe preeclampsia the markers suggested marked bone resorption.

CONCLUSION

Increased bone resorption and decreased bone formation occur in preeclampsia in both mother and fetus, being more pronounced in the latter. The increased osteoclastic activity in preeclampsia may be attributed to increased RANKL induced by increased interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-alpha), and transforming growth factor beta2 (TGF-beta2) production.

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.

Bone metabolic changes during pregnancy: a period of vulnerability to osteoporosis and fracture

Changes in bone density and bone markers suggest that pregnancy is associated with deterioration of bone mass in the mother. The metabolism of calcium resets to allow for the needs imposed by the building of the fetal skeleton. The fetus contributes to the process through the output of regulators from the placenta. Understanding of the whole process is limited, but some changes are unambiguous. There is an increase in the circulating levels of vitamin D, but its functional impact is unclear. Fetal parathyroid hormone (PTH) and PTH-related peptide (PTHrp) play an indirect role through support of a calcium gradient that creates hypercalcemia in the fetus. Placental GH, which increases up to the end of pregnancy, may exert some anabolic effects, either directly or through the regulation of the IGF1 production. Other key regulators of bone metabolism, such as estrogens or prolactin, are elevated during pregnancy, but their role is uncertain. An increase in the ratio of receptor activator of nuclear factor kappa B ligand (RANKL) to osteoprotegerin (OPG) acts as an additional pro-resorbing factor in bone. The increase in bone resorption may lead to osteoporosis and fragility fracture, which have been diagnosed, although rarely. However, the condition is transitory as long-term studies do not link the number of pregnancies with osteoporosis. Prevention is limited by the lack of identifiable risk factors. When fractures are diagnosed, rest, analgesics, or, when indicated, orthopedic intervention have demonstrated efficacy. Systemic treatment with anti-osteoporotic drugs is effective, but the potential harm to the fetus imposes caution in their use.

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.

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.

Regulation of placental calcium transport and offspring bone health

Osteoporosis causes considerable morbidity and mortality in later life, and the risk of the disease is strongly determined by peak bone mass, which is achieved in early adulthood. Poor intrauterine and early childhood growth are associated with reduced peak bone mass, and increased risk of osteoporotic fracture in older age. In this review we describe the regulatory aspects of intrauterine bone development, and then summarize the evidence relating early growth to later fracture risk. Physiological systems include vitamin D, parathyroid hormone, leptin, GH/IGF-1; finally the potential role of epigenetic processes in the underlying mechanisms will be explored. Thus factors such as maternal lifestyle, diet, body build, physical activity, and vitamin D status in pregnancy all appear to influence offspring bone mineral accrual. These data demonstrate a likely interaction between environmental factors and gene expression, a phenomenon ubiquitous in the natural world (developmental plasticity), as the potential key process. Intervention studies are now required to test the hypotheses generated by these epidemiological and physiological findings, to inform potential novel public health interventions aimed at improving childhood bone health and reducing the burden of osteoporotic fracture in future generations.

Histomorfometria óssea de ratas hipertireóideas lactantes e não-lactantes

O objetivo deste estudo foi verificar se o hipertireoidismo potencializa a osteopenia causada pela lactação. Foram utilizadas 24 ratas adultas distribuídas em quatro grupos: eutireóideo não lactante (controle), eutireóideo lactante, hipertireóideo não-lactante e hipertireóideo lactante. Todos os animais foram necropsiados, 20 dias após a gestação. As vértebras torácicas e lombares, o fêmur e a tíbia foram colhidos, descalcificados e submetidos à análise histomorfométrica. O grupo eutireóideo lactante apresentou osteopenia intensa em todos os sítios ósseos estudados. No grupo hipertireóideo não-lactante, não houve alteração da porcentagem de tecido ósseo trabecular nos sítios analisados. No grupo hipertireóideo lactante, havia osteopenia na tíbia e no fêmur, semelhante à do grupo eutireóideo lactante. Mas a porcentagem de tecido ósseo trabecular em todos os corpos vertebrais foi significativamente maior em comparação ao grupo eutireóideo lactante. Conclui-se que o hipertireoidismo não agrava a osteopenia lactacional em ratas, mas minimiza a osteopenia vertebral por estimular a atividade osteoblástica.

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.

Changes in bone density and metabolism in pregnancy

OBJECTIVE

The impact of pregnancy on maternal bone density remains unclear. As a prerequisite to investigate the pathophysiology of gestational bone metabolism, we sought to document the changes in bone metabolism biochemistry in conjunction with those in selective trabecular/cortical osteodensitometry between early and late pregnancy.

METHODS

A prospective, controlled study in a university hospital was conducted with 43 healthy women, 34 of them during uneventful pregnancy. The main outcome measures are trabecular and cortical bone density measured in the first and third trimesters using peripheral quantitative computed tomography in conjunction with a panel of bone metabolism parameters, including blood parathyroid hormone, calcitonin, osteocalcin, skeletal alkaline phosphatase, and the urinary desoxypyridinoline/creatinine ratio.

RESULTS

Cortical bone density was unaffected by pregnancy. Trabecular bone density changes showed wide interindividual variation, ranging from +1.3 to -20.7% per year, identified as fast losers (less than -3%) and slow losers (more than -3%). Serum osteocalcin levels were lower in slow versus fast bone losers in both trimesters (first: P=0.02, third: P=0.02) and were the only independent parameter to differentiate between fast and slow losers.

CONCLUSIONS

Our data suggest that wide interindividual variation and the failure to provide a separate measure of trabecular bone density account for the conflicting evidence in earlier reports. Serum osteocalcin concentration during the first trimester distinguishes between fast and slow losers of trabecular bone and should be evaluated in future studies as predictor for later bone loss (osteoporosis).

Bone turnover from early pregnancy to postweaning

BACKGROUND

To elucidate the sequences of changes in bone metabolism and bone density during pregnancy, lactation and postweaning.

METHODS

Women were recruited (n = 254) in early pregnancy and followed for 2 years. Markers of bone formation (osteocalcin) and resorption (NTx) were measured at five occasions. Bone mineral density (BMD) of whole-body and lumbar spine L1-L4 (DXA) and ultrasonography of os calcis were measured in a subgroup (n = 14).

RESULTS

NTx appeared bone specific in comparison to pyridinolines. NTx started to increase early in pregnancy and remained elevated during lactation (p < 0.001). Osteocalcin was low during pregnancy, but peaked during lactation (p < 0.018). The subsequent decrease was associated with time since resumption of menses (r2 = 0.23; p < 0.001). There was indication of a decrease in calcaneal bone mass during pregnancy and an evident decrease in lumbar spine (p = 0.041) and os calcis (p = 0.037) during lactation. No detectable decrease was identified in whole-body BMD (p = 0.090) during lactation, but in general, BMD was higher in whole-body (1.9%) and lumbar spine (6.6%) 18 months postpartum than during puerperium (p = 0.003).

CONCLUSION

According to the bone metabolic markers, bone resorption increased early in pregnancy and remained elevated over lactation, while bone formation increased during lactation, probably regulated by mechanisms associated with absence of menses. The high metabolic bone turnover during late pregnancy and lactation lead to a decline in cancellous bone mass during lactation, but this seemed beneficial for BMD postweaning.

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.

Quantitative ultrasound (QUS) of bone in the management of postmenopausal women

OBJECTIVES

Postmenopausal osteoporosis is becoming a major problem for healthcare institutions as it has a growing social and economic impact. The incidence of osteoporotic fractures is constantly increasing due to the increase in life expectancy. The gynaecologist plays an important role in establishing a "biological zero" in each perimenopausal patient, and controlling the rate of bone loss during postmenopausal period.

RESULTS

Dual energy X-ray absorptiometry (DXA) has been widely used for the diagnosis and management of osteoporosis and represents a strong risk factor for fractures, but it presents several limitations with regards to diagnosis, treatment follow-up and differential diagnosis of secondary osteoporosis. In these last years quantitative ultrasound (QUS) technique has been introduced for the evaluation of bone status in postmenopausal women and several in vitro and clinical studies have demonstrated the reliability of the examination in terms of: reproducibility, evaluation of fracture risk, treatment follow-up, differential diagnosis. QUS has proven to be equally capable in the prediction of future osteoporosis related fractures in comparison to DXA. Large-scale cross-sectional and longitudinal studies have demonstrated the applicability of QUS in screening the female population during the climacteric period. QUS technique seems to be very efficient in identifying "fast losers", identifying subjects at risk for osteoporosis requiring second-level investigation (DXA, X-ray), diagnosing secondary osteoporosis.

CONCLUSION

If QUS is used in a systematic and rational manner in clinical practice, it is a valid technique for the prevention of osteoporosis in postmenopausal women.

Effects of Nutrient and Food Intake on Calcaneous Bone Mass among Healthy Japanese Women in the Predelivery and Postpartum Periods

OBJECTIVE

To clarify the dietary factors affecting change in calcaneous bone mass during the predelivery and postpartum periods in healthy Japanese women.

METHODS

The calcaneous bone mass was measured as the osteo sono-assessment index (OSI) using the quantitative ultrasound method in 76 Japanese women who were pregnant between February and June 2000. These women subsequently experienced normal pregnancy and labor and could be followed until the sixth month after delivery at an obstetrics and gynecology clinic center located in metropolitan Tokyo. After the intraindividual changes in the OSI during the follow-up period were determined, the relationship between the OSI or OSI change from gestation to the postpartum period and the estimates of nutrient and food intake obtained using a 140-item semiquantitative food frequency questionnaire (FFQ) were analyzed using stepwise multiple regression analysis.

RESULTS

Iron intake in gestation was a significant positive correlate with the percentage change in the OSI between week 36 of gestation and day 5 after delivery (p < 0.001) and that between week 36 of gestation and month 6 after delivery (p < 0.001) (partial regression coefficient of energy-adjusted iron intake, beta = 0.493 mg/day and 0.342 mg/day, respectively). Intake of vitamin D and fruits and vegetables during gestation and/or postpartum was positively associated with the OSI change from week 36 of gestation to the postdelivery stage, whereas the OSI change was inversely related to the intake of carotene, sodium chloride, and meat in the gestation or postpartum period.

CONCLUSIONS

Sufficient intake of iron, vitamin D, or fruits and vegetables may be important for the preservation of bone mass after delivery.

Pattern of bone markers during pregnancy and their changes after delivery

OBJECTIVE

To investigate whether bone resorption markers change during pregnancy and lactation, and how they are correlated with human placental lactogen (hPL) and PRL.

SUBJECTS

Young women before pregnancy, during pregnancy and during a 12-month post-delivery period (study group; n = 22); and age- and weight-matched normal cycling women (control group; n = 22) for a 20-month-period participated in the study.

RESULTS

In the study group, women both during pregnancy (from the 8th up to the 38th week) and during a 6-month period of lactation, pyridinoline and deoxypyridinoline urinary levels were significantly higher than those of pre-pregnancy and control women. They returned to basal values at the 12th post-delivery month. During pregnancy there were early and late peak increases, at the 8th and 32nd week, respectively. At the 32nd, 34th, 36th and 38th week of pregnancy, pyridinoline and deoxypyridinoline urinary values were significantly correlated with hPL serum levels.

CONCLUSIONS

During pregnancy the maternal bone resorption seems to vary critically at early and late stages. A complete reversal of these variations seems to occur after lactation. Further studies could evaluate if changes in placental function are capable of differently interfering with maternal bone resorption.

Release of lead from bone in pregnancy and lactation

Concentrations and isotope ratios of lead in blood, urine, 24-h duplicate diets, and hand wipes were measured for 12 women from the second trimester of pregnancy until at least 8 months after delivery. Six bottle fed and six breast fed their infants. One bottle feeder fell pregnant for a second time, as did a breast feeder, and each was followed semicontinuously for totals of 44 and 54 months, respectively. Bone resorption rather than dietary absorption controls changes in blood lead, but in pregnancy the resorption of trabecular and cortical bone are decoupled. In early pregnancy, only trabecular bone (presumably of low lead content) is resorbed, causing blood leads to fall more than expected from hemodilution alone. In late pregnancy, the sites of resorption move to cortical bone of higher lead content and blood leads rise. In bottle feeders, the cortical bone contribution ceases immediately after delivery, but any tendency for blood leads to fall may be compensated by the effect of hemoconcentration produced by the postpartum loss of plasma volume. In lactation, the whole skeleton undergoes resorption and the blood leads of nursing mothers continue to rise, reaching a maximum 6-8 months after delivery. Blood leads fall from pregnancy to pregnancy, implying that the greatest risk of lead toxicity lies with first pregnancies.

Prenatal and childhood influences on osteoporosis

Osteoporosis is a major cause of morbidity and mortality through its association with age-related fractures. Although most effort in fracture prevention has been directed at retarding the rate of age-related bone loss, and reducing the frequency and severity of trauma among elderly people, evidence is growing that peak bone mass is an important contributor to bone strength during later life. The normal patterns of skeletal growth have been well characterized in cross-sectional and longitudinal studies. It has been confirmed that boys have higher bone mineral content, but not volumetric bone density, than girls. Furthermore, in both genders there is a dissociation between the peak velocities for height gain and bone mineral accrual. Puberty is the period during which volumetric density appears to increase in both axial and appendicular sites. Many factors influence the accumulation of bone mineral during childhood and adolescence, including heredity, gender, diet, physical activity, endocrine status and sporadic risk factors such as cigarette smoking. Measures for maximizing bone mineral acquisition, particularly through encouraging physical activity and adequate dietary calcium intake, are likely to affect the risk of fracture in later generations. In addition to these modifiable factors during childhood, evidence has also accrued that the risk of fracture might be programmed during intrauterine life. Epidemiological studies have demonstrated a relationship between birthweight, weight in infancy and adult bone mass. This appears to be mediated through modulation of the set-point for basal activity of pituitary-dependent endocrine systems such as the hypothalamic - pitutiary - adrenal (HPA) and growth hormone/insulin-like growth factor I (GH/IGF-I) axes. Maternal smoking, diet and physical activity levels appear to modulate bone mineral acquisition during intrauterine life; furthermore, both low birth size and poor childhood growth are directly linked to the later risk of hip fracture. The optimization of maternal nutrition and intrauterine growth should also be included within preventive strategies against osteoporotic fracture, albeit for future generations.

Effect of pregnancy on bone mineral density in healthy women

Despite numerous studies and case reports of changes in bone mineral density (BMD) during pregnancy, the postpartum, and lactation, controversy exists regarding the time course of BMD changes and recovery to baseline levels. The degree to which pregnancy affects BMD long-term remains unclear. Several influencing factors, including breast-feeding, length of amenorrhea after pregnancy, and parity, have been studied with respect to changes in BMD in healthy women. We conducted the first systematic review of its kind on this topic and evaluated the 23 identified citations according to the U.S. Preventive Services Task Force rating scale. Six studies qualified as Level II-2, 12 were Level II-3, and 5 were Level III. There seems to be good evidence that calcium is mobilized from the maternal skeleton to that of the developing fetus during pregnancy. However, the eventual return of BMD to prepregnancy values suggests that maternal bone loss may not be permanent. Results from the studies that specifically evaluated the effect of lactation on BMD were varied, ranging from a decrease in BMD to no change. Of the studies that evaluated the effect of parity on BMD, none found an association linking a greater number of pregnancies to greater decreases in BMD. Pregnancy-associated osteoporosis seems to be uncommon, based on the limited published reports. Overall, no long-term adverse clinical effects have been noted in healthy women who had at least one ongoing pregnancy, despite the good evidence that some bone loss does occur soon after delivery. Additional longitudinal studies need to be undertaken to provide more definitive information on the effects of pregnancy on BMD and risk of osteoporosis later in life.

Biochemical markers of maternal bone turnover are elevated in pre-eclampsia

OBJECTIVES

To investigate the hypothesis that bone turnover is reduced in pre-eclampsia compared with normal pregnancy.

DESIGN

A prospective cross-sectional study.

SETTING

Obstetric unit at the Chelsea and Westminster Hospital, London.

METHODS

Third trimester maternal plasma levels of the cross-linked carboxyl-terminal telo-peptide of type I collagen (ICTP), (a marker of bone resorption) and the carboxyl terminal pro-peptide of type I pro-collagen (PICP), (a marker of bone formation) were compared in 25 women with pre-eclampsia and in 24 normal pregnant controls. The subjects were matched for maternal age, booking body mass index and gestational age. PICP and ICTP levels were measured by radio-immunoassay.

RESULTS

ICTP and PICP levels were significantly increased in women with pre-eclampsia compared with the normal pregnant controls (P = 0.0001 and P = 0.004, for ICTP and PICP respectively, Wilcoxon signed ranked test). There was no significant correlation between either of the markers and booking body mass index, blood pressure, serum uric acid levels or platelet count.

CONCLUSIONS

These data suggest that bone turnover is increased in established pre-eclampsia compared with normal pregnancy. Further studies are required to investigate whether this precedes the onset of the disease.

Calcium in pregnancy and lactation

Pregnancy and lactation are periods of high calcium requirement. This review highlights recent advances in our understanding of calcium and bone metabolism during human pregnancy and lactation and discusses the findings in relation to the calcium nutrition of the mother. The evidence indicates that pregnancy and lactation are characterized by physiological adaptive processes that are independent of maternal calcium intake and that provide the calcium necessary for fetal growth and breast-milk production without requiring an increase in maternal calcium intake. There are firm data that demonstrate that a low calcium intake during lactation does not lead to impaired lactational performance or to exaggerated bone loss. However, more research is required to define whether a low calcium intake prior to or during pregnancy can have deleterious effects on reproductive and lactational performance, and on the long-term health of the mother and child.

Postmenopausal osteoporosis management

Osteoporosis is perhaps the widest-ranging social, physical, and economic impact of estrogen deficiency. Postmenopausal bone loss is the major determinant of osteoporosis. Osteoporotic risk can be determined by measuring bone mineral density using dual X-ray absorptiometry. The radiation free quantitative bone ultrasound is emerging in the assessment of bone structure giving reliable estimates of fracture risk. Diet and exercise are important in determining a woman's risks for osteoporosis. Hormone replacement therapy clearly decreases bone turnover and prevents postmenopausal bone loss and reduces fractures. Tibolone as well as raloxifene prevent bone loss and solid data demonstrate a reduction of vertebral fractures after raloxifene administration.

Calcium levels in maternal milk: relationships with calcium intake during the third trimester of pregnancy

The aim of the present study was to investigate the relationship of Ca intake and serum Ca levels during the third trimester of pregnancy with levels of the same mineral in transition milk (days 13-14 of lactation) and mature milk (day 40 of lactation). The study subjects were a group of fifty-seven healthy, lactating mothers aged between 18 and 35 years (mean 27 (SD 3.7) years) whose pregnancies and labour were attended by the Department of Obstetrics and Gynaecology of Cuenca INSALUD Hospital, Spain. Ca intake during the third trimester was determined by recording the consumption of foods over a 5 d period and by registering Ca provided by dietary supplements. The same method was used to investigate the intake of protein, vitamin D, fibre and Fe, nutrients that could affect the use of dietary Ca. Ca levels in maternal serum during this stage of pregnancy, during lactation and in transition and mature milk samples, were determined using 2-cresolphthalein complexone. During pregnancy 70.2% of subjects showed Ca intakes below 1100 mg/d (75th percentile). The consumption of Ca supplements was very small and hardly modified the mean quantity supplied by the diet. Subjects with an intake < 1100 mg/d showed no fall in Ca levels in serum, either during pregnancy or lactation, nor were decreased levels found in transition milk. However, these subjects showed lower Ca levels in mature milk (5.95 (SD 1.56) mmol/l) than did subjects with greater Ca intakes (6.82 (SD 1.31) mmol/l). This may suggest that breast-fed babies of mothers with lower Ca intakes during pregnancy also receive less Ca.

Hazards of heparin: allergy, heparin-induced thrombocytopenia and osteoporosis

Heparin is the commonest mode of thromboprophylaxis used in pregnancy. It does not cross the placenta but has potential adverse effects on the mother, of which the most important is heparin-induced osteoporosis. The hazards of heparin, including bleeding, skin reactions, heparin-induced thrombocytopenia and osteoporosis are discussed and the relevant literature reviewed. Low-molecular-weight heparins have certain advantages over standard unfractionated heparins, especially in obstetrics. Their longer half-life and increased bioavailability enable once-daily injections, making them more convenient and acceptable. They are as effective as standard heparin but have a theoretically more favourable side-effect profile, providing less anticoagulant relative to antithrombotic activity. Current evidence suggests a lower incidence of heparin-induced thrombocytopenia. A reduced risk of osteoporosis is suggested but not yet proven. Although thrombo-embolism is currently the leading cause of maternal mortality in the UK, antenatal heparin prophylaxis is not given to all women with previous thrombo-embolism because of continued fears concerning heparin-induced osteoporosis. A protocol is presented with guidelines for different levels of obstetric prophylaxis depending on the perceived level of risk.