Effect of bed rest during pregnancy on bone turnover markers in pregnant and postpartum women

Effective strategies for pregnancy and lactation-associated osteoporosis: teriparatide use in focus

INTRODUCTION

Pregnancy and lactation-associated osteoporosis (PLO) is a rare condition characterized by fragility fractures occurring during late pregnancy or lactation, primarily affecting the spine and causing significant morbidity and back pain. PLO can lead to mobility impairment and work incapacity, with recovery taking up to several years. Due to the lack of clinical trials, treatment strategies remain poorly defined, historically focusing on calcium supplements, vitamin D, and weaning from breastfeeding. However, recent attention has turned to teriparatide (TPD) as an option due to its anabolic properties and potential suitability for women of childbearing age.

METHODS

This review evaluates TPD's use in PLO treatment, using published systematic reviews and case studies. Over 300 cases with PLO were identified through PubMed, Google Scholar, and Cochrane searches until August 2023.

RESULTS

We identified 175 cases with PLO treated with TPD alone or followed by antiresorptive therapy. Most women (85.7%) were primiparas. The mean ± SD duration of TPD use was 15 ± 6 months. Among the study patients, 91.4% used TPD alone, while 8.6% (15/175) utilized sequential therapy. Approximately 93% of our cohort exhibited potential risk factors for PLO. Despite the increased risk of recurrent fractures in PLO, only 14.7% (20/175) of those treated with TPD sustained new fractures during a 9-month to 9 years' follow-up period. The mean ± SD percent increase in BMD at the LS was 21.14% ± 7.4%, and at the FN it was 12.1% ± 9.3%. The baseline Z-scores at the LS ranged from -3.3 (-3.7 to -2.7), while the baseline Z-scores at the FN ranged from -2.0 (-2.7 to -1.5).

CONCLUSION

This review emphasizes PLO severity, advocating for increased awareness and timely interventions. TPD emerges as a promising therapeutic option in certain cases.

Mechanical protein polycystin-1 directly regulates osteoclastogenesis and bone resorption

Mechanical loading is required for bone homeostasis, but the underlying mechanism is still unclear. Our previous studies revealed that the mechanical protein polycystin-1 (PC1, encoded by Pkd1) is critical for bone formation. However, the role of PC1 in bone resorption is unknown. Here, we found that PC1 directly regulates osteoclastogenesis and bone resorption. The conditional deletion of Pkd1 in the osteoclast lineage resulted in a reduced number of osteoclasts, decreased bone resorption, and increased bone mass. A cohort study of 32,500 patients further revealed that autosomal dominant polycystic kidney disease, which is mainly caused by loss-of-function mutation of the PKD1 gene, is associated with a lower risk of hip fracture than those with other chronic kidney diseases. Moreover, mice with osteoclast-specific knockout of Pkd1 showed complete resistance to unloading-induced bone loss. A mechanistic study revealed that PC1 facilitated TAZ nuclear translocation via the C-terminal tail-TAZ complex and that conditional deletion of Taz in the osteoclast lineage resulted in reduced osteoclastogenesis and increased bone mass. Pharmacological regulation of the PC1-TAZ axis alleviated unloading- and estrogen deficiency- induced bone loss. Thus, the PC1-TAZ axis may be a potential therapeutic target for osteoclast-related osteoporosis.

Ultrasonographic changes in quadriceps femoris thickness in women with normal pregnancy and women on bed rest for threatened preterm labor

This study aimed to evaluate the changes in quadriceps femoris muscle thickness during the pregnancy and postpartum periods and to elucidate the effect of bed rest for threatened preterm labor on muscle thickness. In 26 women with normal pregnancy, quadriceps femoris thickness was measured at 11-13, 26, 30, and 35 weeks' gestation, and at 3-5 days and 1 month postpartum using ultrasonography. In 15 pregnant women treated with bed rest for threatened premature labor, quadriceps femoris thickness was measured at 30 and 35 weeks' gestation and postpartum. In women with normal pregnancy, quadriceps femoris thickness increased, peaking at 35 weeks' gestation, followed by a postpartum decrease. In women on bed rest, quadriceps femoris thickness showed no significant change during the pregnancy and postpartum periods, and the muscle was significantly thinner at 35 weeks' gestation than that in women with normal pregnancy. In conclusion, a significant increase in quadriceps femoris muscle thickness during normal pregnancy was found using ultrasonography. Meanwhile, in pregnant women on bed rest treatment, the quadriceps femoris was significantly thinner in the late third trimester than that in normal pregnant women. Prolonged bed rest can affect normal changes in the quadriceps femoris muscle thickness during the pregnancy and postpartum periods.

Society for Maternal-Fetal Medicine Consult Series #50: The role of activity restriction in obstetric management: (Replaces Consult Number 33, August 2014)

Despite current recommendations against its use, activity restriction remains a common intervention used to prevent preterm birth in multiple clinical settings. Hypertensive disorders of pregnancy, preterm premature rupture of membranes, multiple gestations, vaginal bleeding, short cervical length, placenta previa, and fetal growth restriction are also common reasons for antepartum hospital admission and frequently lead to a recommendation for activity restriction. However, numerous reports have shown that activity restriction does not prevent adverse obstetrical outcomes but does confer significant physical and psychosocial risks. This consult reviews the current literature on activity restriction and examines the evidence regarding its use in obstetrical management. The recommendations by the Society for Maternal-Fetal Medicine are as follows: (1) we recommend against the routine use of any type of activity restriction in pregnant women at risk of preterm birth based on preterm labor symptoms, arrested preterm labor, or shortened cervix (GRADE 1B); (2) we recommend against the use of routine inpatient hospitalization and activity restriction for the prevention of preterm birth in women with multiple gestations (GRADE 1A); and (3) given the lack of data definitively demonstrating that activity restriction improves perinatal outcome in pregnancies complicated by fetal growth restriction, preterm premature rupture of membranes, or hypertensive diseases of pregnancy, coupled with evidence of adverse effects of activity restriction, we suggest that activity restriction not be prescribed for the treatment of pregnancies complicated by fetal growth restriction, preterm premature rupture of membranes, or hypertensive disease (GRADE 2B).

Tocolysis: A Review of the Literature

Importance

Preterm delivery represents an important cause of infant morbidity and mortality. Various tocolytics have been studied with the objective of stopping preterm labor, increasing gestational age at delivery, and preventing complications related to preterm birth.

Objective

This review aims to summarize the major classes of tocolytics and review the evidence regarding use of each.

Evidence Acquisition

A PubMed search of the following terms was performed to gather relevant data: "tocolytic," "preterm labor," "preterm delivery," "PPROM," "magnesium," "indomethacin," "nifedipine," and "betamimetics."

Results

The benefits and risks of nonsteroid anti-inflammatory drugs, calcium channel blockers, magnesium, and betamimetics are reviewed. Calcium channel blockers afford superior outcomes in terms of prolonging gestation and decreasing neonatal morbidity and mortality with the fewest adverse effects.

Conclusions and Relevance

Tocolytics, particularly calcium channel blockers, may provide benefit to pregnant women and their infants. Their use should be tailored to the particular clinical circumstances of the patient and used in conjunction with other management strategies (e.g., administration of corticosteroids for fetal lung maturation or magnesium for neuroprotection and transfer to a tertiary medical center). Further research and professional guidelines are needed on optimal use of these agents.

Restricted physical activity in pregnancy reduces maternal vascular resistance and improves fetal growth

OBJECTIVES

To test the efficacy of maternal activity restriction for reducing peripheral vascular resistance in normotensive pregnant women with raised total vascular resistance (TVR) and to evaluate its effect on fetal growth.

METHODS

This was a prospective case-control study of 30 women enrolled between 27 and 29 weeks' gestation. All patients met the following criteria: normal blood pressure before and during pregnancy, TVR between 1300 and 1400 dynes × s/cm⁵ at enrolment, normal fetal Doppler parameters at enrolment and abdominal circumference between the 10^th and 25^th centiles. Patients were assigned to activity restriction (activity-restriction group; n = 15) or no treatment (control group; n = 15) and were assessed after 4 weeks for TVR and fetal growth.

RESULTS

TVR at enrolment and estimated fetal weight centile were similar in the activity-restriction group vs controls (1358 ± 26 vs 1353 ± 30 dynes × s/cm⁵ ; 18^th  ± 4 vs 19^th  ± 4 centile; P = NS). After 4 weeks, the activity-restriction group compared with controls showed significantly lower TVR (1165 ± 159 vs 1314 ± 190 dynes × s/cm⁵ ; P < 0.05), which was associated with higher estimated fetal weight centile (25^th  ± 5 vs 20^th  ± 5 centile; P < 0.05). TVR was lower and estimated fetal weight centile higher for the activity-restriction group after 4 weeks compared with at enrolment.

CONCLUSIONS

In normotensive pregnant women with raised TVR, maternal activity restriction appears to be effective in reducing TVR and therefore enhancing fetal growth. Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd.

Practice Bulletin No. 159: Management of Preterm Labor

Preterm birth is the leading cause of neonatal mortality and the most common reason for antenatal hospitalization . In the United States, approximately 12% of all live births occur before term, and preterm labor preceded approximately 50% of these preterm births . Although the causes of preterm labor are not well understood, the burden of preterm births is clear-preterm births account for approximately 70% of neonatal deaths and 36% of infant deaths as well as 25-50% of cases of long-term neurologic impairment in children . A 2006 report from the Institute of Medicine estimated the annual cost of preterm birth in the United States to be $26.2 billion or more than $51,000 per premature infant . However, identifying women who will give birth preterm is an inexact process. The purpose of this document is to present the various methods proposed to manage preterm labor and to review the evidence for the roles of these methods in clinical practice. Identification and management of risk factors for preterm labor are not addressed in this document.

Activity restriction increases deoxypyridinoline excretion in hospitalized high-risk pregnant women

PURPOSE

Activity restriction (AR), one of the most common interventions used in high-risk pregnancies, may exacerbate loss of bone mass. The purpose of this study was to determine changes over time in bone resorption in hospitalized AR women during late pregnancy.

METHODS

This was a short-term prospective study conducted in two tertiary-care obstetric hospitals. We measured urinary deoxypyridinoline (Dpd) excretion, a marker of bone resorption, once per week in a convenience sample of 14 hospitalized AR women in the third trimester and compared values at 28-31 and 34-36 weeks' gestation to those of 11 ambulatory control women. Both groups completed a bone-loading questionnaire, 3-day food intake record, and pedometer step counts at the same gestational age.

RESULTS

Urinary Dpd excretion increased from Days 1-7 (2.60 ± 0.32 nmol/mmol creatinine) to Days 22-28 (5.36 ± 0.83 nmol/mmol creatinine; p ≤ .05). Dpd excretion was higher in AR women (4.51 ± 0.31 nmol/mmol creatinine) than ambulatory women (2.72 ± 0.39 nmol/mmol creatinine) at 34-36 weeks' gestation (p ≤ .05). Energy intake between ambulatory and AR women was not different (p ≥ .05). All women met the daily requirements for calcium and vitamin D intake during pregnancy. Average daily pedometer steps for the AR women were significantly less compared to controls (1,329 ± 936 and 8,024 ± 1,890 steps/day, respectively; p ≤ .05).

CONCLUSIONS

AR leads to increased bone resorption in hospitalized pregnant women, which may impact future risk of developing osteopenia and osteoporosis.

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

Objective

To evaluate whether bone mineral density (BMD) changes in women engaged in active exercises during pregnancy would be different from non-exercising women.

Methods

Consecutive patients with singleton pregnancies who were engaged in active exercise training during pregnancy were prospectively recruited over a period of 6 months. Quantitative USG measurements of the os calcis BMD were performed at 14–20 weeks and at 36–38 weeks. These patients were compared to a control cohort of non-exercising low-risk women.

Results

A total of 24 physically active women undergoing active physical training of over 10 h per week at 20 weeks gestation and beyond (mean 13.1 h, SD 3.3) were compared to 94 non-exercising low-risk women. A marginal fall in BMD of 0.015 g/cm² (SD 0.034) was demonstrable from early to late gestation in the exercising women, which was significantly lower than that of non-exercising women (0.041 g/cm²; SD 0.042; p = 0.005). Logistic regression models confirmed that active exercises in pregnancy were significantly associated with the absence of or less BMD loss in pregnancy.

Conclusion

In women actively engaged in physical training during pregnancy, the physiological fall in BMD during pregnancy was apparently less compared to those who did not regularly exercise.

Bone Status in Activity-Restricted Pregnant Women Assessed Using Calcaneal Quantitative Ultrasound

Objective:

Pregnancy-induced bone loss may be further exacerbated by activity restriction (AR). The authors compared the bone status of AR hospitalized (≥7 days) pregnant women in the third trimester to ambulatory (AM) women at the same gestational age, using a prospective cross-sectional design.

Method:

AR was quantified in AR women by daily step counts using a pedometer for 7 consecutive days. Bone status was evaluated in the left and right calcaneus bones of both AR ( n = 13) and AM ( n = 20) women using quantitative ultrasound (QUS).

Results:

AR women took an average of 1,504 ± 1,377 steps/day. Speed of sound scores (1,543.05 ± 41.97 m/s vs. 1,569.60 ± 46.12 m/s) and broadband ultrasound attenuation (BUA) scores (107.93 ± 9.59 dB/MHz vs. 114.69 ± 17.06 dB/MHz) were not different between the AR and AM groups, respectively ( p > .05). However, bone stiffness index (SI) scores (84.0 ± 16.2 vs. 95.8 ± 22.1, respectively, p < .05) were different between groups, indicating a greater relative risk of future fracture in the AR women.

Conclusion:

Increased fracture risk appears to be a negative side effect incurred through an average of 16 days of hospitalized AR in late pregnancy. Further investigations using a larger sample size are necessary to evaluate the effect of antepartum AR on bone status in the postpartum period to determine if bone status is further attenuated by breastfeeding or if recovery occurs with resumption of ambulation and return of menses and to assess future risk in these women as they age. Prenatal care providers should be made aware of these risks.

Differences in bone metabolism between singleton pregnancy and twin pregnancy

OBJECTIVE

The objective of this study was to examine the influence of twin pregnancy on calcium metabolism, including bone turnover markers and calcium-regulating factors, by comparison between singleton pregnancy and twin pregnancy in women during pregnancy and puerperium in cross-sectional and longitudinal studies.

METHODS

Women with singleton and twin pregnancies were recruited from the outpatient clinic of Tokushima University Hospital. In both cross-sectional and longitudinal studies, bone formation and resorption markers, mineral metabolism and calcium-regulating factors were measured at 10, 25, 30 and 36 weeks of pregnancy and at 4 days and 1 month postpartum in women with singleton and twin pregnancies.

RESULTS

Urinary levels of cross-linked type I collagen N-telopeptides and C-terminal telopeptides of type I collagen in women with twin pregnancy were significantly higher than those in women with singleton pregnancy and those high levels were observed earlier than those in women with singleton pregnancy. In the cross-sectional study, serum levels of bone-specific alkaline phosphatase, calcium and phosphate in women with twin pregnancy were higher and the levels of 1,25-(OH)2 vitamin D and 25-(OH) vitamin D in women with twin pregnancy were lower than those in women with singleton pregnancy.

CONCLUSION

Changes in bone metabolism in women with twin pregnancy are different from those in women with singleton pregnancy. Early and large increases in bone turnover markers allow women with twin pregnancy to meet high fetal demand for calcium during pregnancy.

Biochemical basis of circadian rhythms and diseases: With emphasis on post-traumatic stress disorder

Circadian rhythms affect several processes in the body physiology. This commentary revisits the topic of 'metabolic basis of diseases' with a view to shed light on how cellular energy requirements feed-forward to a sequential signaling of hormonal response, blood glucose metabolism, antioxidant activities, and pathophysiology. Attempt is made to explain how diseases that may not appear to be closely related, such as bone metabolism and vasculopathy, have an increase in oxidative damage as a common underlying biochemistry. Importantly, this article identifies oxidative damage as an outcome of sleep disturbance and hypothesize that sleep complaint is not merely one of many resulting symptoms of PTSD, but a core feature that arise from trauma and gives rise to the stress biochemistry, which in turn manifests symptomatically. Further, we suggest that the current non-pharmacologic and pharmacologic therapeutic options attenuate oxidative stress. Implication for clinical diagnosis and evaluations is also suggested.

Lack of evidence for prescription of antepartum bed rest

Antepartum bed-rest treatment is based on assumptions that it is both effective and safe for mother and fetus. However, research indicates, that bed-rest treatment is ineffective for preventing preterm birth and fetal growth restriction, and for increasing gestational age at birth and infant birthweight. Studies of women treated with pregnancy bed-rest identify numerous side effects, including muscle atrophy, bone loss, weight loss, decreased infant birthweight in singleton gestations and gestational age at birth, and psychosocial problems. Studies conducted by aerospace scientists who have used bed rest as a model for the study of weightlessness in space using nonpregnant individuals report similar results. Antepartum bed-rest treatment should be discontinued until evidence of effectiveness is found.

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.

Maternal circulating osteoprotegerin and soluble RANKL in pre-eclamptic women

OBJECTIVE

To evaluate alterations in the concentrations of osteoprotegerin (OPG), RANKL and the OPG/RANKL ratio in pre-eclamptic women during the puerperium.

STUDY DESIGN

This cross-sectional study was performed in the maternity ward of Aretaieio Hospital in Athens, Greece. Fifteen pregnant women with severe pre-eclampsia and 15 matched controls with premature rupture of the membranes were recruited. Fasting blood samples were obtained antepartum, immediately after diagnosing pre-eclampsia (median: 32nd gestational week), and during the 3rd-6th day postpartum, to estimate levels of circulating OPG and RANKL as well as the OPG/RANKL ratio. The anthropometric parameters evaluated included body mass index and blood pressure.

RESULTS

Mean circulating OPG levels decreased significantly in both groups in the postpartum period (controls: 43.7 ± 19.1 ng/ml vs 22.9 ± 9.1 ng/ml, p = 0.008; pre-eclamptic group: 72.3 ± 49.9 vs 49.7 ± 40.9 ng/ml, p = 0.002). The antepartum OPG/RANKL ratio was elevated in hypertensive pregnancies (2.41 ± 1.72) compared to normotensive pregnancies (1.45 ± 0.63), but the difference did not reach statistical significance (p = 0.1). The OPG/RANKL ratio decreased in the control group (0.76 ± 0.30, NS) following delivery, while it remained unchanged in the pre-eclamptic women (1.63 ± 1.40, p = 0.13). Consequently, the postpartum OPG/RANKL ratio was significantly higher in the pre-eclamptic women compared to control women (1.63 ± 1.40 vs 0.76 ± 0.30, p = 0.01). Levels of RANKL demonstrated no significant alterations during puerperium in both cases.

CONCLUSION

Pregnancies complicated with pre-eclampsia exhibit higher OPG levels and OPG/RANKL ratios, compared to control pregnancies, which might be compatible with lower bone turnover. The significance of this finding with respect to bone metabolism remains to be elucidated in larger studies.

Influence of long-term thromboprophylaxis with low-molecular-weight heparin (enoxaparin) on changes of bone metabolism markers in pregnant women

This is a first descriptive, retrospective, observational study aiming to evaluate the changes in bone turnover markers in pregnant women and to assess the effect of a long-term treatment with low-molecular-weight heparin (LMWH), specifically, enoxaparin. Study involved 50 pregnant Caucasian women with thrombophilia. The patients either received prophylactic enoxaparin once daily subcutaneously (N = 35) or were observed without treatment (N = 15). Concentrations of total serum alkaline phosphatase (total AP), bone alkaline phosphatase (bone AP), osteoprotegerin (OPG), and the receptor activator of nuclear factor κB ligand (RANKL) were measured at 15, 25, and 35 weeks of gestation. Total serum AP increased with gestational age. In the group treated with enoxaparin, the percentage of bone AP concentration was lower (P < .05) than in the control group. Serum OPG also increased with gestational age, but no significant difference was found between the groups with- and without treatment. Despite the OPG increased, RANKL did not change.

Maternal activity restriction and the prevention of preterm birth

Activity restriction is 1 of the most common interventions used in obstetrics. Although it is used for many reasons, 1 of the most common is to prevent preterm birth in those at risk. This review of the literature describes the potential advantages, disadvantages, and efficacy of activity restriction for the prevention of preterm birth.

Perinatal bone turnover in term pregnancies: the influence of intrauterine growth restriction

Intrauterine growth restriction (IUGR) has been associated with low bone mass in infancy and increased risk for osteoporosis development in adult life. We aimed to investigate the effect of IUGR on bone metabolism in mother/infant pairs, by determining circulating biochemical markers of bone turnover in IUGR and appropriate for gestational age (AGA) pregnancies. Circulating markers of bone formation [bone specific alkaline phosphatase (BALP), total alkaline phosphatase (ALP), osteocalcin (OC)] and bone resorption [cross-linked N-telopeptide of type I collagen (NTx)], as well as intact parathormone (PTH), calcium and phosphorus levels were measured in 40 mothers and their 20 IUGR and 20 AGA singleton full-term fetuses and neonates on postnatal days 1 (N1) and 4 (N4). No significant differences in BALP, ALP, OC, NTx, PTH, calcium or phosphorus levels were observed between the AGA and the IUGR groups. In both groups, maternal BALP levels were lower compared to fetal, N1 and N4 levels (p< or =0.005 in all cases). In the AGA group, maternal NTx and OC levels were lower compared to fetal, N1 and N4 levels (p<0.001 in all cases), and fetal NTx levels were lower compared to N1 and N4 ones (p<0.001 and p=0.002, respectively). In the IUGR group, maternal OC levels were lower compared to fetal, N1 and N4 ones (p<0.001 in each case) and fetal OC levels were elevated compared to N1 and N4 ones (p<0.001 and p=0.003, respectively). N4 NTx levels were elevated compared to maternal, fetal and N1 levels (p=0.009, p<0.001 and p=0.002, respectively) and fetal NTx levels were lower compared to N1 and N4 ones (p=0.001 and p<0.001, respectively). Finally, positive correlations were found between maternal NTx and BALP (r=0.332, p=0.037), as well as ALP (r=0.329, p=0.038) levels, and between maternal, fetal, N1, N4 BALP and respective ALP levels (r=0.432, p=0.005, r=0.534, p=0.001, r=0.778, p<0.001, r=0.694, p<0.001, respectively). In conclusion, maternal, fetal and neonatal bone turnover in IUGR cases may not differ from respective bone metabolism in AGA controls. In addition, fetal and neonatal bone remodeling is markedly enhanced and independent of maternal bone turnover in late pregnancy.