Bone in the pregnant mother and newborn at birth

Bone metabolism in pregnant women exposed to single compared with multiple courses of corticosteroids

OBJECTIVE

To compare markers of maternal bone metabolism between women who received a single compared with multiple courses of antenatal corticosteroids.

METHODS

This is an analysis of serum samples from a previously reported randomized, placebo-controlled, multicenter trial. Women at risk for preterm delivery after an initial course of corticosteroids were randomly assigned to weekly courses of betamethasone (active) or placebo. Serum levels of carboxy terminal propeptide of type I procollagen (PICP) and cross-linked carboxy terminal telopeptide of type I collagen (ICTP) were measured to assess the rate of bone formation and resorption, respectively, at three time points. The placebo group (n=93) was compared with the active group, receiving four or more courses of betamethasone (n=112).

RESULTS

There were significant (P<.001) increases in PICP and ICTP between baseline and delivery in both groups. Cross-linked carboxy terminal telopeptide of type I collagen, but not PICP, was lower with corticosteroid exposure immediately before administration of the fourth study course (P<.001). No significant differences in PICP and ICTP were seen between groups at delivery.

CONCLUSION

Increasing levels of PICP and ICTP with advancing gestation are consistent with physiologic changes in maternal bone metabolism. Multiple courses of corticosteroids for fetal maturation are not associated with persistent or cumulative effects on maternal bone metabolism as measured by PICP and ICTP.

LEVEL OF EVIDENCE

II.

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.

Fetal and postnatal bone development: reviewing the role of mechanical stimuli and nutrition

Fetal and postnatal bone development is by tradition viewed as a process of bone mineral accretion or an increase in bone mass. Accordingly, previous approaches to bone development in neonatology and early childhood have emphasized the determinants of peak bone mass and their relationship to osteopenia, osteoporosis and fractures in later life. This suggests that the neonatal period and early childhood is an important period for bone mineral accrual, and that peak bone mass may be correlated with subsequent skeletal health. Nevertheless, describing fetal and postnatal bone development just in terms of changes in mass or density means looking at bones as if they were amorphous heaps of calcium and phosphorus. In reality, of course, bones are complex three-dimensional structures. It is therefore important to create conditions that stimulate bones to become more stable. We suggest that functional bone physiology can be used to explain fetal and postnatal bone development and to devise strategies for improved bone development in both premature infants and neonates.

The relationship between birth weight, oxidative stress and bone mineral status in newborn infants

BACKGROUND

It was shown that oxygen-derived free radicals, and particularly the superoxide anion, are intermediaries in the formation and activation of osteoclasts. Many antioxidant defence systems depend on micronutrients or are micronutrients themselves. Oxidative stress might be related to bone indices in newborn infants.

AIM

To assess the relationship between oxidative status and bone indices in small-for-gestational-age (SGA), large-for-gestational-age (LGA) and appropriate-for-gestational-age (AGA) babies born to healthy mothers.

METHODS

Umbilical cord venous blood samples were obtained at the delivery from 100 term newborn infants to measure plasma malondialdhyde, superoxide dismutase (SOD) and myeloperoxidase concentrations. Forty of the newborn infants had birth weights AGA, 30 were SGA and 30 LGA. Data were acquired using the whole body dual-energy X-ray absorptiometry scanner in the first 24 h after birth.

RESULTS

Plasma malondialdhyde and SOD concentrations of the mothers and their newborn infants were positively correlated; however, plasma myeloperoxidase concentrations were not. SOD concentrations of SGA infants were significantly higher than those of AGA and LGA infants. Whole body bone mineral density and content were lower in SGA but higher in LGA babies than in AGA babies. Oxidative stress status of both infants and their mothers was not related to the bone indices.

CONCLUSION

Our study does not provide support for the hypothesis that oxidative status of the infants and mothers may play a major role in the regulation of bone metabolism in the developing skeleton.

Bone ultrasound velocity in small- versus appropriate-for-gestational age preterm infants

OBJECTIVE

To compare bone status of small-for-gestational age (SGA) versus appropriate-for-gestational age (AGA) newborn preterm infants.

STUDY DESIGN

Tibial speed of sound (SOS) was measured in 144 infants categorized as SGA or AGA using the reference tables of Lubchenco et al. and Alexander et al.

RESULTS

By the Lubchenco tables, 22% of infants were SGA and 75% were AGA. The mean gestational ages of SGA and AGA were similar (33.3+/-2.6 and 32.5+/-2.4 weeks, respectively, P = 0.09); however, SGA infant birth weights were lower (1329+/-392 and 1829+/-481 g, respectively, P<0.001). SOS values were higher for SGA versus AGA infants (3098+/-135 and 3003+/-122 m/s, respectively. P<0.001). Use of the Alexander tables yielded a twofold increase in the percent of infants categorized as SGA; SOS values remained significantly greater for SGA infants (P<0.001).

CONCLUSION

Higher tibial SOS values in SGA versus AGA infants indicate greater bone strength.

Inadequate prenatal care and elevated blood lead levels among children born in Providence, Rhode Island: a population-based study

OBJECTIVE

This study was conducted to determine whether children born to mothers receiving inadequate prenatal care are at an increased risk for having an elevated blood lead level during early childhood.

METHODS

The authors conducted a population-based study of children born in Providence, Rhode Island, from 1997 to 2001 whose mothers had received adequate, intermediate, or inadequate prenatal care. The children's blood lead levels were compared between groups using bivariate and logistic regression. To understand the regulatory implications and public health impact of changing the definition of an elevated blood lead level, "elevated" was defined as 5 microg/dL, 10 microg/dL, and 15 microg/dL.

RESULTS

Children born to mothers who received inadequate prenatal care were at an elevated risk for having an elevated blood lead level later in life. This relationship remained statistically significant for each definition of elevated blood lead level and after controlling for other socio-economic status measures and birthweight (at 5 microg/dL, odds ratio [OR] = 1.36, 95% confidence interval [CI] 1.09, 1.68, p = 0.006; at 10 microg/dL, OR = 1.68, 95% CI 1.26, 2.24, p < 0.0004; at 15 microg/dL, OR = 1.83, 95% CI 1.10, 3.04, p = 0.019) represent an opportune moment to identify expectant mothers living in lead-contaminated environments.

CONCLUSIONS

Results suggest that conducting lead screening as a regular part of prenatal care provision could help identify women possibly experiencing ongoing lead exposure and help reduce or prevent exposures to their offspring.

In utero physiology: role in nutrient delivery and fetal development for calcium, phosphorus, and vitamin D

Only limited aspects of the transfer of calcium across the placenta to the fetus are known. Clinical outcome studies suggest that bone mineral mass in newborn infants is related to maternal size and dairy intake. Available data indicate that vitamin D deficiency may also limit in utero fetal bone mineral accumulation. Recent data suggest that maternal vitamin D status affects long-term childhood bone status. At present, no strong evidence exists showing that improving maternal calcium or vitamin D status has a long-term positive effect on childhood bone mass. In premature infants, clinical rickets and fractures are common. In utero rates of calcium accretion during the third trimester cannot be readily achieved. The use of fortifiers designed for human-milk-fed infants or specially designed high-mineral-containing formulas allows for bone mineral accretion at or near in utero rates. Recent data have shown that physical therapy programs, judiciously used, in combination with adequate mineral content, can enhance bone mineral mass in preterm infants. There is little evidence for the use of high doses of vitamin D in the management of premature infants. After hospital discharge, continuation of a relatively high mineral intake has been shown to enhance bone mineral acquisition. Future research should include evaluations of the role of maternal vitamin D supplementation on fetal and infant bone mass, the mineral needs of infants weighing <800 g or <25 wk gestation, and the optimal discharge management of premature infants who are at risk of low bone mass.

The relationship between birthweight, 25-hydroxyvitamin D concentrations and bone mineral status in neonates

BACKGROUND

Calcium (Ca), phosphorus (P) and 25-hydroxyvitamin D (25-OHD) are the major micronutrients for fetal skeletal development.

AIMS

To compare whole body bone mineral density (WB BMD) and bone mineral content (WB BMC) in different birthweights of term neonates and to determine correlations of biological criteria of bone health between neonates and their mothers.

SUBJECTS AND METHODS

Serum Ca, P, alkaline phosphatase (ALP) and 25-OHD levels were measured in 30 small-for-gestational-age (SGA, group 1), 40 appropriate-for-gestational-age (AGA, group 2) and 30 large-for-gestational-age (LGA, group 3) neonates and their mothers in winter. WB BMD and WB BMC of neonates were estimated by dual-energy X-ray absorptiometry (DEXA) in the 1st 24 hrs after delivery.

RESULTS

Mean (SD) serum 25-OHD levels in the mothers [8.7 (3.0), 8.6 (3.0) and 7.7 (2.8) microg/L, respectively] and their infants [6.3 (2.5), 6.0 (2.2) and 5.7 (1.8) microg/L, respectively] in groups 1, 2 and 3 were similar. Compared with the mothers, the mean 25-OHD levels of the neonates in all groups were significantly lower (p<0.05), and they were highly correlated (r=0.755, p<0.05). Ninety-three per cent of the neonates and 82% of their mothers had 25-OHD levels <10 microg/L, the lowest limit of normal. Mean (SD) WB BMD and WB BMC were higher in LGA infants [0.442 (0.025) g/cm(2), 71.6 (9.0) g, p<0.01, p<0.001, respectively] but lower in SGA [0.381 (0.027) g/cm(2), 29.1 (9.1) g, p<0.001, p<0.001, respectively] than in AGA infants [0.426 (0.022) g/cm(2), 53.7 (9.6) g, respectively]. The percentage of WB BMC was lower in SGA than in AGA and LGA infants. WB BMC and WB BMD were positively correlated with birthweight (r=0.910, p<0.05) and gestational age (r=0.707, p<0.05) but not with serum 25-OHD.

CONCLUSIONS

The neonates' bone indices increased significantly with gestational age and birthweight but this was not related to serum 25-OHD levels in the infants and their mothers.

Calcium Homeostasis in Human Placenta: Role of Calcium‐Handling Proteins

The human placenta is a transitory organ, representing during pregnancy the unique connection between the mother and her fetus. The syncytiotrophoblast represents the specialized unit in the placenta that is directly involved in fetal nutrition, mainly involving essential nutrients, such as lipids, amino acids, and calcium. This ion is of particular interest since it is actively transported by the placenta throughout pregnancy and is associated with many roles during intrauterine life. At term, the human fetus has accumulated about 25-30 g of calcium. This transfer allows adequate fetal growth and development, since calcium is vital for fetal skeleton mineralization and many cellular functions, such as signal transduction, neurotransmitter release, and cellular growth. Thus, there are many proteins involved in calcium homeostasis in the human placenta.

Increased bone turnover during the third trimester of pregnancy and decreased bone mineral density after parturition in adolescents as compared to age-matched control patients

To evaluate the impact of pregnancy on bone, we studied bone turnover at the first (T1) and third (T3) trimester of gestation in 58 adolescents and 28 healthy adolescents who had never been pregnant. Total body (TB) and lumbar spine (LS) bone mineral density (BMD) and body composition were evaluated by dual-energy X-ray absorptiometry in all control patients (C) and after parturition in 28 pregnant patients (G). Paired and unpaired t tests, Mann-Whitney and Pearson correlation tests were used. Bone turnover markers were above the reference range for adult women in more than 80% of the adolescents, with no difference between C and G patients at T1. Increase in urinary N-telopeptide crosslinks of type I collagen and serum bone-specific alkaline phosphatase, markers of bone turnover, was seen during pregnancy ( p < 0.0001). Body composition did not differ between groups, but LS BMD, percentage of expected LS BMD, LS Z-score, percentage of expected TB BMD and TB Z-score were lower in G than C patients ( p < 0.05). TB BMD was positively correlated with LS BMD (r2 = 0.52). The inverse correlations between bone markers and LS BMD suggest that the increased bone turnover during pregnancy probably explains the low bone density after parturition. The impact on future peak bone mass must be studied.

In search of causative factors of deformational plagiocephaly

This is a preliminary study of 37 infants with deformational plagiocephaly. In this first effort to create a profile of factors that may contribute to the onset and progress of developmental plagiocephaly, parents were interviewed concerning selected practices before and immediately after the birth of their infants. Results of the study do not reveal a clear or concise pattern of factors that may contribute to this condition. There needs to be additional research on the benefits and potential hazards of sleep position to infants as one of the factors that may contribute to deformational plagiocephaly.