Milk Mature. Milk Handjob. Milk Bbw. Milk Asian Big tits. Milk Nipples Ebony Big tits Masturbation. Milk Nipples Big tits Amateur. Milk Mature Uniform. Milk College. Milk Japanese Fetish Couple Rich. See That. Milk Japanese Asian Fantasy Big tits. Milk Hd Milf. Milk Japanese Wife College Big tits. Milk Japanese Teen Big tits. Milk Nipples Blonde Big tits. Milk Blowjob Big tits German. Milk Japanese Big tits Asian Amateur. Milk Ebony Big tits Pornstar. Milk Nipples Japanese Big tits. Milk Bbw Hd Big tits Cute. Milk Blonde Big tits Hardcore. Milk Japanese Big tits Fingering Blowjob. Milk Bdsm Fetish.
Milk Asian Japanese Cunnilingus. Milk Lesbian Compilation. Milk Bdsm Bound Big tits. Nipples Milk Cute Amateur Couple. Milk Japanese Big tits Handjob. Milk Japanese Asian Nipples Big tits. Milk Big tits Asian College Naughty. An additional consideration is that intestinal calcium absorption increases before the fetal demand for calcium; consequently, the excess absorbed calcium must be excreted. As in rodents, pregnancy causes increased creatinine clearance and glomerular filtration rate As early as the 12th week of gestation, the h urine calcium excretion increases significantly, with mean values reaching the upper limit of normal, and values in the hypercalciuric range often observed 18 , , , , , , Fasting urine calcium concentrations are normal or low, confirming that the increase in h urine calcium is due to absorptive hypercalciuria, i.
Since the fetal demand for calcium does not occur until the third trimester, but intestinal calcium absorption increases in the first trimester, this explains why absorptive hypercalciuria is an obligatory, physiological consequence of pregnancy. It is one of the factors that contributes to an increased risk of kidney stones during pregnancy These findings have been interpreted to mean that high-dose vitamin D supplementation does not cause hypercalciuria during pregnancy , , However, since it is absorptive hypercalciuria that occurs during pregnancy, and random spot urines are neither sensitive enough nor timed appropriately to detect absorptive hypercalciuria, the available data have not adequately excluded whether hypercalciuria worsens during pregnancy when high-dose vitamin D is taken.
Twenty-four hour urine collections are needed. In this context, it is relevant to mention that hypocalciuria during pregnancy has been associated with preeclampsia and pregnancy-induced hypertension 42 , , , , In turn, the hypocalciuria has been reported in association with low serum calcitriol , , , , whereas PTH, calcitonin, and ionized calcium are normal 42 , , , The calcitriol levels are reduced to values seen in nonpregnant women.
The possibility that low maternal 25OHD or low vitamin D intake could explain the increased risk of preeclampsia and, thereby, low calcitriol has been investigated with a similar number of studies supporting 46 , 95 , , and refuting , , , an association. The low calcitriol, hypocalciuria, and reduced creatinine clearance that occur in preeclampsia and PIH are likely secondary to disturbed renal function, rather than being causes of the hypertension Consistent with this, in a longitudinal study, calcitriol levels were normal earlier in pregnancy and became low only after hypertension and proteinuria developed Another study found that serum levels of the fat-soluble vitamins A, D, and E were each lower in preeclamptic women compared with normotensive pregnant and nonpregnant controls , which raises the possibility that confounding from overweight, obesity, and poor nutrition may explain why the levels of several fat-soluble vitamins were all lowered in preeclamptic women.
A placental abnormality has been hypothesized to explain lower calcitriol levels in preeclampsia, with conflicting results obtained showing decreased and increased placental expression of Cyp27b1. However, since the placenta contributes very little calcitriol to the circulation of pregnant women see sect. II A4 , it is unlikely that loss of placental Cyp27b1 leads to reduced serum calcitriol in preeclamptic women. Alternatively, abnormal placental function could indirectly reduce maternal calcitriol concentrations if placental hormones such as placental lactogen are important stimulators of Cyp27b1 in the maternal kidneys.
However, plasma concentrations and placental expression of placental lactogen are not reduced in preeclamptic women 73 , 74 , , , , , Numerous clinical trials have been carried out to assess the efficacy of calcium supplementation at preventing preeclampsia or pregnancy-induced hypertension, and a net benefit has been seen for women with the lowest intakes of calcium, whereas no effect is evident for women with adequate calcium intake In multiple clinical trials, no effect of high-dose vitamin D supplementation has been seen on the incidence of preeclampsia in pregnant women , , , , Increased intestinal calcium absorption during pregnancy leads to increased urine calcium excretion, with h urine values near or above the upper limit of normal.
The pregnancy-related suppression of PTH to low values may contribute to increased renal calcium excretion. Hypocalciuria with low calcitriol occurs in preeclampsia, likely as a consequence of disturbed renal function.
Calcium supplementation reduces the risk of preeclampsia in women with the lowest calcium intakes, while vitamin D supplementation has had no effect. The maternal skeleton is a storehouse of mineral that can be resorbed during pregnancy if needed to provide mineral to the fetuses. Additional radioisotope studies have confirmed that some calcium in the maternal skeleton will be resorbed to enter the fetal skeleton, especially during the last few days of gestation However, much less 45 Ca from the maternal skeleton ends up in the fetuses compared with how much enters the milk and the pups during lactation, which confirms that skeletal resorption during pregnancy is quite modest compared with that during lactation The extent to which bone turnover is altered during pregnancy may be deduced from relative changes in biochemical markers of bone formation and resorption.
These measurements are fraught with confounding problems of changes in intravascular volume and glomerular filtration rate discussed in section II D2. In most studies they were measured in late pregnancy only.
The available indices suggest at most a mild uncoupling in favor of resorption during pregnancy in mice, as indicated by normal to modestly increased deoxypyridinoline and CTX, normal P1NP, and decreased osteocalcin , , , , A decline in osteocalcin has also been noted during pregnancy in guinea pigs and sheep , and contrasts with increased osteocalcin found in rats during early pregnancy and at term , The effect that pregnancy has on bone mass or mineralization has been serially assessed by DXA measurements done every day and every other day during reproductive cycles in outbred Black Swiss mice.
The hindlimb increases by a similar amount while the lumbar spine remains unchanged. This increase in whole body bone mineral content is consistent with the previously noted upregulation of intestinal calcium absorption and positive calcium balance. It is noteworthy, in these studies at least, that the maternal skeleton continues to accrete mineral during the last 5 days of gestation despite calcium being transferred to the fetuses at a peak rate. Apart from serial assessment of bone mineral content by DXA at multiple time points during pregnancy in Black Swiss mice, most studies in rodents have simply compared end-of-pregnancy BMC or BMD to prepregnancy in the same mice, or to age-matched virgin mice, without determining whether any changes in bone mass occurred earlier in pregnancy.
This approach has shown that bone mass or mineral content at the end of pregnancy varies significantly by skeletal site and genetic background in mice. CD-1 mice show no significant changes in mineral content during pregnancy at any skeletal site 35 , Rats showed no change in whole body BMD and nonsignificant declines in BMD of femora and tibiae at the end of pregnancy , whereas another study found a modest but significant decline in lumbar spine BMD , and a third study found a gain in femoral and vertebral BMC and BMD Another study found that femoral calcium content at the end of pregnancy was linearly related to the calcium content of the diet Overall, apart from the serial studies in Black Swiss mice, none of the other studies in rodents can confirm or refute whether bone mass increases earlier in pregnancy before declining.
Static and dynamic histomorphometry have been carried out in the femora of pregnant rats and compared with age-matched virgins. The results are inconsistent across studies and not clearly explainable by variations in the calcium content of the diet or the strain of rat. One reported marked increases in bone resorption osteoclast number, resorptive surfaces and bone formation osteoblast number, osteoblast surface, osteoid volume during pregnancy in Cobs rats consuming a 0. Another found that osteoclast parameters increased three- to sixfold while bone formation parameters were unchanged in Sprague-Dawley rats on a 1.
A third study used a 1. In all four studies bone turnover was found to be increased on the basis of at least one parameter i. A calcium-restricted diet in ewes leads to increased resorption and reduced ash weight, particularly within the vertebrae and the pelvis by the end of pregnancy, with relative sparing of the long bones A high calcium diet prevents these changes.
In most histomorphometry, microCT, and electron microscopy studies, despite this apparent increase in bone turnover, there was no net change in femoral or tibial bone mass at the end of pregnancy in Cobs, Holtzman, Lister, and Sprague-Dawley rats on a 0. Exceptions include reduced bone volumes and trabecular thickness in the lumbar spine at the end of pregnancy in Sprague-Dawley rats consuming 1. Other studies have found increases in cortical volumes of the femora , , , increased cortical porosity in the femora , and reduced trabecular bone volumes of the tibiae , all in Sprague-Dawley rats with no correlation to the dietary calcium content.
The available data discussed in this section may seem inconsisent and contradictory. For example, within some of these studies there is histomorphometric evidence of markedly increased bone turnover in late pregnancy but little or no change in bone mass. A problem contributing to the inconsistency is the comparison of a single time point end of pregnancy to prepregnancy or age-matched virgins, without any assessment at intermediate time points.
If a net increase in bone mass and mineralization occurs earlier in pregnancy as suggested by calcium balance studies, upregulated intestinal calcium absorption, and serial DXA studies in Black Swiss mice , and is then followed by upregulated bone resorption with net bone loss during the latter third of pregnancy corresponding to when fetal demand for mineral is at its peak , then that can certainly explain why bone mass may appear relatively unchanged at the end of pregnancy despite objective evidence of significantly increased bone resorption.
Furthermore, even if there was no increase in bone mass earlier in pregnancy, if bone resorption increases only in late pregnancy, that may be too short of a duration to detect a loss in bone volumes by histomorphometry. There are likely site-specific differences as well, with trabecular-rich vertebrae possibly differing in their response to pregnancy compared with more cortical-rich sites such as the tibiae and femora. Increased weight-bearing during pregnancy may contribute to a gain in bone mass of the limbs, as shown in some of the studies.
As noted earlier, when a low calcium diet is consumed, the skeleton will be markedly resorbed, leading to consistently reduced bone mass by the end of pregnancy in rats 64 , , and goats This resorption is mediated in part by compensatory secondary hyperparathyroidism, which is more marked on a calcium-restricted diet see sect.
II A2. Conversely, a high-calcium diet 1. Does the lack of change or small net change in bone mass or volumes at the end of pregnancy have any effect on bone strength? However, the material properties of rat femora were deduced to show reduced shear stress and increased stiffness when subjected to rotational stress Two studies from the same investigator provided contradictory results in that load to failure in the three-point bend test was increased and reduced at the end of pregnancy in Wistar rats compared with age-matched virgins.
The work to failure did not differ between pregnant and age-matched virgins in both studies , , suggesting that there was no real change in bone strength. Although there may be no net change or modest changes in bone mass by the end of pregnancy when a calcium-replete diet is consumed by rodents, there is other evidence that the macro structure of bone may be altered. In Sprague-Dawley rats, an increase in femoral cortical bone volumes, radii, and cortical thickness have been found at the end of pregnancy, which appear to result from increased periosteal bone formation during pregnancy , , , These changes are conceivably a compensatory response to the increased weight bearing during pregnancy and the resorption of trabecular bone.
The change in bone volumes and radii may become more marked during lactation see sect. Bone turnover during pregnancy may be impacted by diverse hormones, including the previously noted increases in estradiol, PTHrP, prolactin, placental lactogen and growth hormone, and oxytocin. That prolactin or placental lactogen may influence bone metabolism directly has been suggested by the finding that osteoblasts express prolactin receptors , , and prolactin receptor deficient mice exhibit decreased bone formation Furthermore, when the prolactin increase during pregnancy was reduced by treating Sprague-Dawley rats with bromocriptine, it blunted the pregnancy-related gain in femoral and vertebral bone mineral content The oxytocin receptor is expressed by osteoclasts and osteoblasts , which may enable oxytocin to regulate bone metabolism during pregnancy.
In support of this, oxytocin and oxytocin receptor-null mice of both sexes have reduced bone formation and an osteoporotic phenotype Oxytocin also stimulates osteoblast differentiation and function, whereas it stimulates osteoclast formation but inhibits osteoclast function and skeletal resorption , An in vivo role for oxytocin has not been examined in these mice.
Intestinal calcium absorption increases in the first trimester, months before the fetal demand for mineral in the third trimester. Metabolic studies have shown that women are in a positive calcium balance by mid-pregnancy , so skeletal mineral content may become increased at that time-point to explain where that calcium is stored. Some maternal bone resorption during late pregnancy may contribute mineral to the fetus.
This has shown by study of women living near the Techa River in Russia, who inadvertently ingested 90 Sr from water contaminated by nuclear waste during the s. Years after the exposure ended, 90 Sr could be detected in the skeletons of their fetuses, which could only have come from resorption of 90 Sr that had been previously fixed in the maternal skeleton , But women who ingested 90 Sr during pregnancy, especially during the third trimester, gave birth to babies with fold higher 90 Sr content, consistent with dietary absorption of mineral being responsible for much more of the mineral content of the fetal skeleton , , The sole study reporting iliac crest histomorphometry during human pregnancy was carried out in 15 women who planned to have elective first trimester abortions, 13 women scheduled to have C-sections in the third trimester, and 40 nonpregnant women some living and some cadaveric specimens At the first trimester time point, bone resorption indexes were increased, bone formation indexes were decreased, and trabecular bone volume was significantly lower, compared with nonpregnant women Conversely, the third-trimester biopsies were no different from the nonpregnant values for bone mass and indexes of bone resorption and formation Taken at face value, these results suggest that early pregnancy is a bone-resorptive state, which induces bone loss that is later recovered by the end of pregnancy.
That interpretation does not fit easily with the fact that little transfer of calcium is occurring from mother to offspring during the first trimester; consequently, skeletal resorption should not be increased at this time point, especially given that intestinal calcium absorption is already upregulated. Instead, increased bone resorption is more likely to occur in the third trimester when the fetal demand for mineral is at its peak.
The observed differences may be the result of small sample sizes with confounding among the groups. Age matching was poor and may have contributed to apparent differences, with mean ages of More histomorphometric data from pregnant women are needed. Cross-sectional and serial measurement of bone turnover markers have been carried out in pregnant women. These indexes are generally considered more accurate at detecting changes in bone resorption compared with bone formation and are subject to diurnal variation as well as differences between fasted and postprandial values , , Pregnant women were often compared with nonpregnant controls or normal ranges, rather than prepregnancy measurements from the same women.
Additional potential confounders include hemodilution affecting serum measurements confirmed to affect osteocalcin and CTX, Ref. Correcting for the decline in serum albumin obliterated the apparent fall in serum CTX earlier in pregnancy Osteocalcin has been the most widely used marker of bone formation, and its values have been low to undetectable in the first trimester, after which it may stay low or rise to normal values by term 33 , , , , , , , , Its apparent decline early in pregnancy was attributable to hemodilution of pregnancy in one study , whereas a surge in osteocalcin after delivery of the placenta is compatible with loss of placental degradation or clearance Procollagen I N-telopeptides P1NP and carboxypeptides, and bone specific alkaline phosphatase, are also low in the first trimester, and have either remained low , or risen to normal or above by term 85 , , , , Total alkaline phosphatase increases mainly due to the placental fraction and is not a useful indicator of the relative changes in bone formation during pregnancy 33 , 85 , , , The overall pattern of results suggests that bone turnover may be relatively normal earlier in pregnancy but that it increases during the third trimester to create a net resorptive state.
Such a pattern would be consistent with the expected late-pregnancy demand for mineral and, thereby, a concurrent need to resorb from the maternal skeleton, especially if intestinal absorption of mineral is not sufficient to meet the combined needs of mother and fetus.
Twin pregnancy resulted in slightly higher urinary NTX and CTX, and a slightly increased bone-specific alkaline phosphatase at term; these findings are compatible with further increased resorption to meet the needs of two fetuses Cross-sectional and serial studies of areal bone mineral density have been carried out in pregnant women. Most studies have been done before and after a planned pregnancy to avoid fetal radiation exposure, so very limited information is available about changes in maternal BMD during pregnancy. The readings may also be affected by altered body composition, weight, and skeletal volumes during pregnancy.
An early study used X-ray spectrophotometry of the radius and femur during the first or second trimester and found that trabecular but not cortical bone density had decreased by the time of a postpartum measurement Several prospective studies used single- or dual-photon absorptiometry SPA or DPA of the forearm serially during and after pregnancy 18 , , , or of the femur before and after a planned pregnancy, and found no significant changes in cortical or trabecular bone density More modern studies have used DXA at two time-points, 1—8 mo before planned pregnancy and 1—6 wk after delivery 85 , , , , , , However, the largest study involved 92 women who had DXA of hip, spine, and radius done at baseline up to 8 mo prior to planned pregnancy ; DXA of the forearm repeated during each trimester; and DXA of hip, spine, and radius repeated 15 days postpartum.
Seventy-three women completed the postpartum visit and were compared with 57 nonpregnant women who had DXA measurements done at similar intervals. When the prepregnancy to postpregnancy readings were compared, BMD was reduced by 1. Overall, this study found statistically significant but small declines in BMD at several skeletal sites. For perspective, it is important to realize that such changes would not be distinguishable from error of measurement in an individual subject, but were resolvable in this study due to the large cohort. In contrast, radial BMD was measured in a longitudinal study of 22 women and a cross-sectional study of 75 women, and no change was seen across the three trimesters in either study Peripheral ultrasound has been used during pregnancy.
Cross-sectional , and longitudinal studies , , , , , , have found lower apparent BMD in the os calcis or phalanges at the end of pregnancy, but no effect was seen on the mid-tibial shaft How relevant peripheral ultrasound at the heel or a finger during pregnancy is for revealing changes in bone mass or mineralization at the spine or hip is uncertain.
Notably, although bone mass declines significantly during lactation, with the most marked changes in the lumbar spine see sect. IV E , ultrasound of the os calcis and mid-tibial shaft showed no changes , , Overall, available data suggest that bone turnover increases during pregnancy, especially during the third trimester. There are real but small declines in BMD throughout the skeleton that require a sufficiently large cohort to be detected with confidence.
Are there any long-term impacts of skeletal changes induced by pregnancy? This has been examined through numerous epidemiological studies that have ascertained whether parity confers any risk of lower BMD, an osteoporotic level of BMD, or fragility fractures. The majority of such studies have found either a neutral effect of parity 16 , 38 , 63 , 71 , 83 , , , , , , , , , , — , , , , , , , , , , , , , , , , , , , , , , , , , , , or that parity confers greater BMD 27 , , , , , , , , , , , , , , , , , , Additional studies have reported that parity decreases the risk of hip fractures , , , , , , , One of the studies reporting a protective effect of parity was particularly strong because it involved 1, twins and their female relatives, including 83 identical twins who were discordant for ever being pregnant For balance, a few studies have found that parity is associated with reduced BMD 17 , 80 , , , , , or increased vertebral 97 or hip fracture risk However, these reports are substantially outnumbered by the aforementioned studies that found a neutral or protective effect of parity.
There are also divergent effects seen among the different studies. For example, one study reported that parity reduces femoral neck BMD but had no effect on lumbar spine Another found that parity reduces total hip and femoral neck BMD in postmenopausal women, but not in premenopausal women who are closer in time to the event and therefore less likely to show confounding Several studies also found that adolescent pregnancy was associated with decreased bone density , , , even though parity was not a significant factor in the overall cohort.
However, an NHANES study of women ages 20—25 found that adolescent pregnancy did not reduce peak bone mass as previously feared, since BMD was no different regardless of whether these women had experienced an adolescent pregnancy, an adult pregnancy, or no prior pregnancies These epidemiological studies have a number of limitations. It is difficult to separate the effects of parity from those of lactation. Decades have passed in some cases between the reproductive years and the time of the first BMD measurement or fracture, such that confounding factors and events in the elapsed time may have influenced the outcome.
Such confounding may be less likely in the NHANES study involving women ages 20—25 since the pregnancies were only a few years earlier, wherein no detrimental effect of parity was seen. Overall, it seems most likely that parity has no long-term adverse effect on BMD or fracture risk for most women. It is not recognized as a significant factor for estimating yr risk of fracture in FRAX However, there may be a subset of women in whom parity does adversely affect bone mass.
These may include women in whom significant nutritional deficiencies lead to increased skeletal resorption during pregnancy to meet the fetal mineral requirements, and some of these women may present with fractures from pregnancy-associated osteoporosis see sect. III A. Animal models suggest that bone mass may increase earlier in pregnancy, whereas by the end of pregnancy bone mass is approximately equal to or slightly lower than prepregnancy or age-matched virgin values.
Bone turnover as assessed by histomorphetry and bone resorption and formation markers increases during late pregnancy in a pattern that predicts that some degree of bone loss has occurred in these animal models. Whether there is any net loss of bone mass by the end of pregnancy depends on the degree to which bone mass increased earlier in pregnancy. Late pregnancy is the interval of increased secondary hyperparathyroidism in rat studies. Bone strength is probably unchanged at the end of pregnancy. Some inconsistencies among the rat data increased, decreased, or no change in bone turnover, mass, or strength are not obviously explainable by the calcium content of the diet or the rat strain used.
However, it is clear that skeletal resorption and net bone loss increase in animal models when a calcium-restricted diet is given during pregnancy. Available data from pregnant women indicate that a positive calcium balance also occurs by mid-pregnancy, but whether BMD is objectively increased at this time point has not been determined. Upregulation of bone resorption occurs in the third trimester and likely causes some bone loss, with most women ending up with either no change or a very modest decrease in BMD by term.
Increased resorption and net bone loss are more likely to occur in women who do not absorb sufficient calcium to meet the combined needs of themselves and their babies. Inadequate dietary calcium intake probably contributes to an increased risk of pregnancy-associated osteoporosis see sect. In the long term, these pregnancy-related changes in bone metabolism or bone mass appear to have no adverse effect on the calcium content or strength of the maternal skeleton, and may even have a protective effect against low BMD and future risk of fractures.
Fragility fractures do not normally occur as a result of pregnancy in animal models. This is consistent with upregulation of intestinal calcium absorption usually being sufficient to meet the mineral requirements of the fetuses, and the finding that bone strength is unchanged at term. However, it is clear that the maternal skeleton will be resorbed when the maternal diet is inadequate.
A low-calcium diet provokes marked secondary hyperparathyroidism during pregnancy , but even then, spontaneous fractures have not been noted until lactation Osteoporotic fractures during pregnancy are very uncommon, but they do occur. They have probably been occurring in association with reproduction for the past five millennia, because vertebral compression fractures and low BMD have been found in Egyptian mummies and other archaeological skeletons of women who were 16—30 yr of age when they died Osteoporosis presenting in pregnancy has been reviewed in depth recently , and will be covered more briefly here.
There are two main presentations: vertebral fractures and so-called transient osteoporosis of the hip. Fragility fractures of the spine and less commonly other skeletal sites have occurred during the third trimester, and in the puerperium of women who did not breastfeed. In both situations these fractures may be considered to have been provoked by pregnancy fractures during lactation are considered separately in sect. In most affected women there is no preceding bone mineral density BMD reading because of no prior indication for it to have been done.
Serum chemistries and calciotropic hormone levels are usually unremarkable. However, bone loss is likely a factor in pregnancy-related vertebral fractures, because the BMD is usually low at presentation , , , , and it spontaneously improves afterward , , In the few cases where bone biopsies were done, mild osteoporosis was observed , , Insufficient calcium absorption from dietary calcium deficiency, lactose intolerance, celiac disease, other malabsorptive disorders, and vitamin D deficiency is likely to induce resorption of the maternal skeleton during the third trimester.
A recent report described a woman with a calcium intake of mg daily, who developed multiple vertebral compression fractures during pregnancy Since that amount was insufficient for her own nonpregnant needs, the normal upregulation of intestinal calcium absorption during pregnancy would not have benefited her. Significant skeletal resorption was an inevitable consequence of her pregnancy. Another potential cause of physiological bone loss during pregnancy is greater than normal release of PTHrP from the placenta and breasts.
The gradual rise in plasma PTHrP sect. II A3 likely contributes to upregulation of calcitriol synthesis, intestinal calcium absorption, and bone turnover in all pregnant women. However, in individual reported cases, high circulating levels of PTHrP have arisen from the breasts or placenta and led to pseudohyperparathyroidism, which is characterized by increased bone resorption and severe hypercalcemia see sect.
III F , , , High circulating levels of PTHrP that contributed to bone resorption have also been noted in women who presented with fragility fractures weeks after delivery 29 , ; such high levels may have begun in pregnancy and contributed to bone loss before delivery.
Additional factors that contribute to fracture risk during pregnancy include increased weight-bearing average weight gain of 12 kg , lordotic posture, reduced bone mass or strength that precedes pregnancy, and conditions that cause bone loss during pregnancy. Published cases have revealed such diverse conditions as anorexia, longstanding hypomenorrhea or relative estradiol deficiency, premature ovarian failure, petite stature or body frame, mild osteogenesis imperfecta, inactivating mutations in LRP5 , dietary calcium deficiency, renal calcium leak hypercalciuria , bedrest and inactivity, and pharmacotherapy before or during pregnancy that may induce bone loss [heparin, oral glucocorticoids, gonadotropin releasing hormone GnRH analogs, depot medroxyprogesterone acetate, and certain anticonvulsants] A maternal family history of severe osteoporosis is likely to be present in women with pregnancy-associated fragility fractures , which implies that genetic causes of low bone mass or skeletal fragility may be present.
Pregnancy-associated osteoporosis typically occurs in a first pregnancy, higher parity does not increase the risk, and fractures usually do not recur in subsequent pregnancies , , , , These observations imply that in many cases reversible factors such as nutritional deficiencies may have been corrected after the first pregnancy. Permanent disorders such as osteogenesis imperfecta or LRP5 mutations should be anticipated to maintain an increased risk of vertebral and other fractures in subsequent pregnancies. Many uncontrolled treatments [nasal calcitonin , , , bisphosphonates 43 , , , , , , , , , , , , strontium ranelate , , and teriparatide 98 , , , , , ] have been reported in various case series.
Therefore, the attributable effect of pharmacological therapy may have been greatly overestimated. It may be reasonable to wait 12—18 mo for spontaneous recovery to occur before evaluating whether the fracture risk remains high enough to warrant pharmacological therapy Transient osteoporosis of the hip in pregnancy also known as bone marrow edema syndrome is a rare condition of skeletal fragility.
It appears to be a form of chronic regional pain syndrome 1 or reflex sympathetic dystrophy that most often involves the hips , , , , When it occurs in association with pregnancy, its onset is usually during the third trimester or the puerperium with unilateral hip pain, limp, or a hip fracture; it can also be bilateral at presentation , , , , , The femoral head and neck are osteopenic and radiolucent on plain radiographs , , , while DXA suggests that the hip BMD is quite low The lumbar spine BMD is usually normal but if it is also low, it is usually substantially higher than the femoral neck BMD Magnetic resonance imaging MRI studies have revealed that the radiolucent femoral head and neck are edematous, which suggests that the low DXA values in the hip may be an artifact of that increased water content 31 , , , Nevertheless, that bone marrow edema is still an indication of fragility in the affected femora, and prophylactic arthroplasties have been carried out in women in whom the fracture risk was considered to be high.
Whether that is a real increase in mineralization or removal of an artifact from bone marrow edema remains uncertain. The etiology of this condition is uncertain. It occurs equally in men and women, and its occurrence during pregnancy may simply be by chance. It might also be triggered by pregnancy-related factors. Femoral venous stasis caused by pressure from the pregnant uterus, relative immobilization from bed rest, and fetal pressure on the obturator nerve are among the theories proposed to explain its occurrence in pregnant women , , , , , It is considered separately here because, unlike the vertebral and other fractures that sometimes occur during pregnancy, it does not seem to result from systemic bone resorption.
It also has different epidemiological characteristics, including that it can occur in any pregnancy, and it has recurred in the other hip either during a subsequent pregnancy or when not pregnant. Therefore, the two conditions can coincide, despite evidence that they appear to have a different pathogenesis and outcome. Partial data for the United States indicate an annual kill of 6, seals in Angliss and Outlaw, However this does not include other areas where bearded seals are an important component of the diet.
Local hunting also takes place in Canada Cleator estimated that roughly 2, bearded seals were taken per year. The hunts in Greenland take about , Reijnders et al. These figures do not include seals that are lost during hunting because they sink when killed and cannot be retrieved.
Currently, of the European seal-hunting nations, only Norway is signatory to the Convention, while Russia is not, and Greenland, though part of Denmark, is not committed to the EU legislation. A major concern at the moment is probably the effects that changes in the Arctic climate may be having on the bearded seal's environment, both through changes in water flow and the transport of nutrients through the Bering Strait, and also the loss of ice habitat caused by such factors as global warming Kovacs and Lydersen, In addition there are concerns that oil and gas exploration and extraction in many parts of the species' range, particularly in the Chukchi and Beaufort Seas and the North Sea Route, may cause disturbance to bearded seals as well as possible pollution of the seals, their habitat and their food supply Wiig et al.
The bearded seal shares two features with monk seals, which are unusual for phocid seals - they have straight, no-beaded whiskers and they have four teats instead of the usual two King, Bearded seals are usually found singly in seasonally ice-covered waters. During the ice season they prefer to inhabit areas of broken pack ice and drifting ice floes, but are quite versatile and also occur in areas of shorefast ice and thick ice where they are able to maintain breathing holes. Many of the seals move long distances to follow the receding ice in the summer Kovacs, In other areas such as the Laptev, Okhotsk and White Seas they do not follow the ice, but spend the summer in open water, sometimes hauling out on land, preferably on gravel beaches Burns, Bearded seals have also been reported as hauling out and swimming in rivers that empty into Hudson Bay Kelly, ; Kovacs, Young bearded seals in Alaska may be found in open water, not associated with ice, in summer and autumn.
When hauled out on an ice floe, bearded seals are characteristically seen at the edge of the floe with their head pointing towards the water and downwind. In such as position a seal can move rapidly into the water, can hear and smell what is behind it and see what is in front. Thus this position gives maximum protection aganst polar bear attack Kingsley and Stirling, Pupping and moulting take place on the ice. Most pups are born from mid-March to early May, later in the north than in the south.
Pups are often born on small ice floes immediately adjacent to open water, thus making them less vulnerable to polar bear predation than if they are born on fast ice Kovacs et al. Some, but not all, of the lanugo is moulted in utero Kovacs et al. There is often a lighter region down the centre of the back and some white on the snout and crown King, ; see photo above. Kovacs et al describe a newborn pup entering the water when it was 2h old and swimming with its mother for short periods.
Every 3h this pup called to its mother, who then hauled out on to the ice floe and nursed it. A study of four nursing pups Lydersen et al. The four pups moved with their mothers over a range of nearly 20km between the head and the mouth of the fjord. The mothers appeared to guide their pups away from drifting pack-ice and into more sheltered waters near the edge of the fast ice Hammill et al. The early aquatic ability of the pups may have evolved as a means of escaping predation by polar bears Kovacs et al.
The pup is nursed for about days, although this time may vary. It gains weight very quickly at about 3. Weaning seems to be less abrupt than in most phocid species, with some pups learning to catch small prey while they are still nursing Lydersen et al. The mother ovulates towards the end of the nursing period and mates around that time. Moulting usually takes place after mating, between March and May according to the location King, Bearded seals are benthic foragers, preferring to feed at the seabed at water depths of less than m Gjertz et al. A study of the stomach content of 78 seals in the Bering Sea in early spring Antonelis et al.
Adult males, females and juveniles all had a similar diet. Their large array of moustachial whiskers may be used in the manner of walruses to sort out the smaller food animals in their diet, which they may then suck up, also similarly to walruses King, However, they are generalized predators, also able to take pelagic schooling fish such as capelin Antonelis et al,