Differences in bone metabolism between singleton pregnancy and twin pregnancy

Bone Metabolism, Bone Mass, and Bone Structure During Pregnancy and Lactation: Normal Physiology and Pregnancy and Lactation-Associated Osteoporosis

This article reviews bone metabolism, bone mass, and bone structure changes expected during and after pregnancy and lactation, as well as the condition of pregnancy and lactation-associated osteoporosis (PLO)-a presentation with fragility fracture(s) in the context of these physiologic changes. Clinical implications of physiologic bone changes will be addressed, as will specific management considerations that apply to premenopausal women with PLO.

Are Twin Pregnancies at Higher Risk for Iron and Calcium Deficiency than Singleton Pregnancies?

The aim of this study was to compare the iron and calcium status in singleton and twin pregnancies and to assess whether there is an increased risk for iron and calcium deficiency in twin gestation. The study included 105 singleton and 9 twin pregnancies at or above 35 weeks of gestation. Information on prenatal supplementation with iron or calcium was acquired, and adverse perinatal outcomes were recorded. Biosamples from all 114 mothers and 73 newborns (61 singleton and 12 twin newborns) were finally analyzed. Total iron and calcium concentrations in serum were measured through total reflection X-ray fluorescence analysis. The results indicated no significant differences in maternal serum iron and calcium concentrations between singleton and twin pregnancies. Similarly, iron and calcium concentrations in newborn umbilical cord serum samples were not different between singleton and twin pregnancies. The comparison of total iron and calcium between mothers and umbilical cord serum indicated significantly lower concentrations in the mothers, with the differences being not homogenous but rather pair-specific. A significant positive correlation between maternal serum and umbilical cord serum calcium concentration was noticed. Prenatal iron supplementation was associated with higher iron concentrations in both mothers and newborns, supporting the efficiency of supplementation and the quality of the study methods. Collectively, the data indicate no significant differences in serum iron and calcium concentrations with regard to singleton or twin pregnancies and the efficiency of iron supplementation during pregnancy for increasing iron status.

Evaluation of Vitamin D Status and the Analysis of Risk Factors of Vitamin D Deficiency in Twin Pregnancies

OBJECTIVE

Optimization of maternal vitamin D (VD) status has beneficial effects on pregnancies, but little is known about it of twin pregnancies (TP). Our aim was to promote the current understanding of VD status and its associated factors in TP.

METHODS

We performed liquid chromatography-tandem mass spectrometry to quantify 25-hydroxyvitamin D [25(OH)D] and used the enzyme-linked immunosorbent assay method to detect vitamin D binding protein (VDBP) in 218 singleton pregnancies (SP) and 236 TP.

RESULTS

Levels of 25(OH)D and VDBP were higher in TP than SP. The 25(OH)D, free 25(OH)D, C-3 epimer of 25-hydroxyvitamin D [epi-25(OH)D], and VDBP all increased with gestational progress. Age, body 
mass index, and hemoglobin level were associated with VD deficiency (VDD). Analysis of covariance demonstrated that the 25(OH)D and VDBP of TP and SP still showed differences after adjusting for the above associated factors.

CONCLUSION

Differences in VD status were found in SP and TP, suggesting that the assessment of VD status in TP should be treated with caution. High VDD prevalence is observed among pregnant Chinese women, and it is recommended to promote evaluation for VDD.

A Scoping Review of the Apparent Phenomenon of the Improvement in Hypoparathyroidism in Pregnant and Postpartum Females

Hypoparathyroidism requires management with both calcium supplementation and active vitamin D to avert a state of hypocalcemia. During late gestation and the postpartum period (specifically lactation), there is an under-recognized, yet intriguing occurrence of apparent 'pseudohyperparathyroidism', whereby supplementation dosages may need to either be reduced or discontinued, to prevent hypercalcemia. The explanation for this apparent phenomenon of improved parathyroid status ('remission' or 'resolution') is incompletely understood; the purpose of this review is to analyze the case reports of this enigma within the medical (and grey) literature, providing an overall pathophysiological explanation and recommendation for the management of such patients. A literature search was conducted through PubMed/Medline, CINAHL, Cochrane Library Database, Scopus, UpToDate, Google Scholar, and the grey literature without a time-restricted period, analyzing all available articles within the literature describing an apparent improvement in parathyroid status in late-gestation and postpartum (lactating) females. Non-hypoparathyroid case reports were also included to further analyze and synthesize an overall likely pathophysiological explanation. Through the literature search, 24 papers were identified covering such a phenomenon in patients with hypoparathyroidism, alongside multiple additional reports of a similar occurrence in patients without underlying hypoparathyroidism. The pathophysiology is believed to occur due to the placental production of parathyroid hormone-related peptide (PTHrP) during gestation, with further production from the lactating mammary glands during the postpartum period. A typical pattern is observed, with increased PTHrP and suppressed PTH throughout both gestation and lactation (present in both normal and hypoparathyroid subjects). The concept of PTHrP-induced hypercalcemia is further demonstrated in patients without hypoparathyroidism, including subjects with placental hypersecretion and mammary gland enlargement. It is evident that patients with hypoparathyroidism may require a dosage reduction during late gestation and lactation, due to the risk for hypercalcemia. In addition to patients with hypoparathyroidism, this pathophysiological phenomenon occurs in unsuspecting patients, demonstrating the need for all clinicians in contact with pregnant females to be aware of this uncommon - yet perilous - occurrence.

Review of Dietary Recommendations for Twin Pregnancy: Does Nutrition Science Keep Up with the Growing Incidence of Multiple Gestations?

Recommendations for nutrition and the use of dietary supplements for pregnant women are updated on regular basis but it remains to be seen to what extent they may be applicable in twin pregnancies. The aim of this narrative review is to present the current state of knowledge about the energy and nutrient demand in twin pregnancy. There is general consensus in literature that the energy demand is higher than in a singleton pregnancy, but there is a lack of position statements from scientific societies on specific energy intake that is required. In turn, recommended maternal weight gain, which favors the normal weight of the neonate, has been determined. There is even a larger knowledge gap when it comes to vitamins and minerals, the body stores of which are theoretically used up faster. The greatest number of studies so far focused on vitamin D, and most of them concluded that its concentration in maternal blood is lower in twin as compared to singleton pregnancy. Few randomized studies focus on iron supplementation and there are no other studies that would assess dietary interventions. In light of a growing incidence of multiple pregnancies, more studies are necessary to establish the nutritional demands of the mother and the course of action for adequate supplementation.

Micronutrients in Multiple Pregnancies-The Knowns and Unknowns: A Systematic Review

Maternal diet and nutritional status are of key importance with regard to the short- and long-term health outcomes of both the mother and the fetus. Multiple pregnancies are a special phenomenon in the context of nutrition. The presence of more than one fetus may lead to increased metabolic requirements and a faster depletion of maternal macro- and micro- nutrient reserves than in a singleton pregnancy. The aim of this systematic review was to gather available knowledge on the supply and needs of mothers with multiple pregnancies in terms of micronutrients and the epidemiology of deficiencies in that population. It was constructed in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses Statement (PRISMA). The authors conducted a systematic literature search with the use of three databases: PubMed/MEDLINE, Scopus and Embase. The last search was run on the 18 October 2020 and identified 1379 articles. Finally, 12 articles and 1 series of publications met the inclusion criteria. Based on the retrieved studies, it may be concluded that women with multiple pregnancies might be at risk of vitamin D and iron deficiencies. With regard to other microelements, the evidence is either inconsistent, scarce or absent. Further in-depth prospective and population studies are necessary to determine if nutritional recommendations addressed to pregnant women require adjustments in cases of multiple gestations.

Elemental content of the placenta: A comparison between two high-risk obstetrical populations, adult women carrying multiples and adolescents carrying singletons

BACKGROUND

The placenta is responsible for the exchange of nutrients and for preventing harmful compounds from entering the fetal circulation. With increasing industrialization, exposures to commercial and toxic metals become a concern for both pregnant women and those planning a pregnancy. The understanding of transport mechanisms and pharmacokinetics for most inorganic elements is incomplete and limited to normal term deliveries.

OBJECTIVES

To obtain novel data on 46 inorganic elements in placentae from two high-risk obstetric populations, women carrying multiples and adolescents carrying singletons, evaluating differences, if present, and identifying predictors of placental content.

METHODS

Placental tissue was collected from adolescents carrying singletons and adults carrying multiples. Elemental content was analyzed using inductively coupled plasma-mass spectrometry (ICP-MS). Multivariate regression and factor analyses were used.

RESULTS

With the exception of Au and Pt, almost all placentae contained quantifiable concentrations of each element analyzed. All placentae contained the essential elements Ca, Fe, Mg, Se and Zn, which clustered together onto the same factor. Most elements were higher in placentae from women carrying multiples. Differences in placental content disappeared after adjusting for maternal age. Rare earth elements (REEs) clustered together and remained higher in the multiples even after adjusting for maternal age.

CONCLUSION

Human placentae contain a wide range of elements, including REEs. Ranges differed considerably between cohorts. Elements with similar chemical properties, like REEs or nutritionally essential elements, clustered together. Maternal age, and therefore longer environmental exposure, was significantly associated with elevated element concentrations in the placenta. Placental concentrations of several metals that are known to be nutritionally essential (e.g., Fe, Ca, Mg, and Zn) did not differ significantly between cohorts, suggesting tight regulation, whereas concentrations of environmental contaminants differed significantly between groups, even after adjusting for maternal age.

Maternal and neonatal vitamin-D status in twin versus singleton pregnancies

AIM

There is a paucity of information on vitamin D status of women with twin pregnancy and their newborns. This case-control study compared maternal and neonatal vitamin-D status in twin versus singleton pregnancies.

METHODS

Subjects included 50 women with twin pregnancy delivering at >28 weeks and 50 gestational-age-matched women with singleton pregnancy delivering during the same period. Maternal and neonatal serum 25-hydroxy vitamin D [25(OH)D] was compared between the two groups using the independent Student's t-test on log values. Serum albumin-adjusted calcium, inorganic phosphate, and intact parathormone levels were also compared.

RESULTS

Maternal vitamin-D deficiency (VDD; serum 25(OH)D < 30 nmol/L) was present in 90% of twin and 88% of singleton pregnancies. The prevalence of neonatal VDD was 89% in twin and 74% in singleton pregnancies (P = 0.03). Maternal serum 25(OH)D was lower in the twin group as compared to the singleton group (14.3 ± 10.47 vs 18.5 ± 12.36 nmol/L; P = 0.02). Mean serum calcium, intact parathormone, and inorganic phosphate were comparable between the women in the two groups. Maternal and neonatal 25(OH)D showed positive correlation in the two groups (P < 0.001). Mean cord blood 25(OH)D was significantly lower in the twins than in singleton newborns (14.8 ± 12.63 vs 22.6 ± 16.68 nmol/L; P = 0.002). The difference persisted even after adjustment for birthweights and maternal serum 25(OH)D. Mean serum calcium was significantly lower in the twins.

CONCLUSION

Twin newborns and their mothers have higher VDD as compared to singleton newborns and their mothers in the VDD population.

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.

Alpha-Tocopherol Concentration in Colostrum and Serum of Women With Premature Labor

OBJECTIVE

The aim of the study was to evaluate and compare the levels of alpha-tocopherol in colostrum milk and serum of mothers with premature birth, classified as severe prematurity and moderate prematurity.

METHODS

Cross-sectional study with 65 women, 18 births classified as severe prematurity (<32 weeks of gestation) and 47 as moderate prematurity (≥32 weeks of gestation). The study only included mothers without any conditions associated with pregnancy and who had a single conception without any malformation. Samples of serum and colostrum were collected during fasting in the immediate postpartum, and alpha-tocopherol was analyzed by high-performance liquid chromatography. To determine the biochemical nutritional status of vitamin E, a serum cutoff (11.6 μmol/L) was adopted. The Student t test for independent variables compared the average concentrations of alpha-tocopherol in serum and colostrum among prematurity groups. Differences were considered significant when P < 0.05.

RESULTS

The alpha-tocopherol concentrations in colostrum were similar in both groups, being 34.5 ± 20.2 μmol/L for women with severe prematurity and 35.1 ± 16.3 μmol/L for moderate prematurity. For the serum of puerperal women with severe prematurity, alpha-tocopherol concentration was, however, lower than in women with moderate prematurity, 22.2 ± 4.4 μmol/L versus 27.1 ± 8.6 μmol/L (P < 0.05). The serum levels of alpha-tocopherol indicated nutritional risk at 5.6% (n = 1) of women with severe prematurity and 4.3% (n = 2) for those with moderate prematurity.

CONCLUSIONS

Severe prematurity affected the levels of alpha-tocopherol in maternal serum; however, the level of prematurity did not change the concentration of vitamin E in colostrum.

Formula fed twin infants with recurrent hypocalcemic seizures with vitamin D deficient rickets and hyperphosphatemia

Vitamin D deficient rickets is generally known to occur in breast fed infants. And excessive phosphate ingestion is a main cause of late onset hypocalcemia in formula fed infants. Here we introduce 45-day-old formula fed hypocalcemic twins with recurrent seizure attacks. They were diagnosed as having both of vitamin D deficient rickets and hyperphosphatemia. Radiologic findings indicated mild rickets and the twins were treated with calcium and alfacalcidol. After 3-5 months of oral supplementation, medication was discontinued in both twins. They showed normal growth and calcium, phosphorus, and vitamin D levels during the 6-month follow-up period. Twins can be at risk for hypocalcemia because of their high risk of vitamin D deficiency, low birth weight, and premature birth. Therefore twin pregnant women need ingestion of sufficient vitamin D and calcium.

Twins and endocrinology

Twins are two independent babies delivered during the same pregnancy and are divided as monozygotic or dizygotic based on their origin. Dizygotic twins are similar to two siblings and have different genetic information. In contrary, monozygotic twins have a similar genetic identity and provide a unique opportunity to evaluate the contribution of genetic and environmental factors of the disease. The endocrine and metabolic disorders affect a large number of the population including the twins. Diabetes, obesity, and autoimmune thyroid disease are the most common endocrine disorders in general practice. It is essential to understand the genetic basis of endocrine disorders for therapy, prognostication and risk assessment for future generations. In this article, we review the endocrine disorders in relation to their occurrence in monozygotic twins to highlight the genetic and environmental contribution.

VitaminA, E, and D deficiencies in tunisian very low birth weight neonates: prevalence and risk factors

BACKGROUND

Preterm neonates are at high risk of vitamin deficiencies, which may expose them to increased morbidity and mortality. This study aimed to determine the prevalence and risk factors for vitamin A, E, and D deficiencies in Tunisian very low birth weight (VLBW) neonates.

METHODS

A total of 607 VLBW and 300 term neonates were included in the study. Plasma vitamins A and E were assessed by high performance liquid chromatography and vitamin D was assessed by radioimmunoassay.

RESULTS

Prevalence of vitamin A, E, and D deficiencies were dramatically elevated in VLBW neonates and were significantly higher than term neonates (75.9% vs. 63.3%; 71.3% vs. 55.5%; and 65.2% vs. 40.4%, respectively). In VLBW neonates, the prevalence of vitamin deficiencies was significantly higher in lower classes of gestational age and birth weight. Vitamin E deficiency was associated with pre-eclampsia [odds ratio (OR) (95% confidence interval, 95% CI), 1.56 (1.01-2.44); p < 0.01] and gestational diabetes [4.01 (1.05-17.0); p < 0.01]. Vitamin D deficiency was associated with twin pregnancy [OR (95% CI), 2.66 (1.33-5.35); p < 0.01] and pre-eclampsia [2.89 (1.36-6.40); p < 0.01].

CONCLUSION

Vitamin A, E, and D deficiencies are very common in Tunisian VLBW neonates and are associated with pre-eclampsia. Improved nutritional and health support for pregnant women and high dose vitamins A, E, and D supplementation in VLBW neonates are strongly required in Tunisia.

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 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.