Calcium metabolism in pregnancy: A review

Pitkin, Roy M.

doi:10.1016/0002-9378(75)90481-0

Cited by 144 publications

(45 citation statements)

References 97 publications

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“…In contrast to the present study, other studies in experimental animals used maternal lead exposure during pregnancy instead of exposure only before pregnancy. These studies typically found reduced birth .weights as a result of lead exposure during pregnancy (8,22,23). The present study extends these findings to lead exposure that occurs well before pregnancy.…”

Section: Resultssupporting

confidence: 84%

“…West et al (18) found an inverse relationship between gestational age and maternal blood lead concentrations, but the latter did not differ significantly for birth weights > 2,500 g versus < 2,500 g. Studies in Kosovo (19,20) (23)(24)(25)(26). Because the skeleton is also the major repository for lead, mobilization of skeletal lead and calcium occurs simultaneously when dietary calcium intake during pregnancy is inadequate.…”

Section: Resultsmentioning

confidence: 99%

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Effects of lead exposure before pregnancy and dietary calcium during pregnancy on fetal development and lead accumulation.

Han

Pfizenmaier

Garcia

et al. 2000

Environ Health Perspect

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Millions of women of cild-bearing age have substantial bone lead stores due to lead exposure as children. Dietary calcium ingested simultaneously with lead eposure can reduce lead absorption and accumulaton. However, the efects of dietary calcium on previously accumulted maternal lead stores and transfer to the fetus have not been investigatedL We studied the effects oflead exposure of female rats at an early age on fetal development during a subsequent pregancy. We gave 5-weekold female Sprague-Dawley rats lead as the acetate in their ddnking water for 5 weeks; controls received equimolar sodium acetate. This was followed by a 1-month period without lead exposure before mating. We randomly assigned prewant rats (n = 39) to diets with a deficient (0.1%) or normal (0.5%) calcium content during pregnancy. A total of 345 pups were delivered alive. Leadexposed dams and their pups had significantly higher blood lead concentrations than controls, but the concentrations were in the range of those found in many pregnant women. Pups bom to dams fd the calcium-deficient diet during pregnancy had higher blood and organ lead concentrations than pups born to dams fed the 0.5% calcium diet. Pups bom to lead-exposed dams had sigificant- controls were simultaneously given equimolar sodium acetate in the drinking water. A 5-week period of lead exposure was followed by a 4-week period without lead exposure. During these periods before mating, the rats consumed diets containing 0.5% calcium. At this time, the rats were 14 weeks of age. The female rats were then mated with 14-weekold male SD rats, with 1 male and 3 females caged together. Of the 76 female rats, 39 (51.3%) were impregnated. Lead-exposed and nonexposed pregnant rats were then randomly assigned to either normal (0.5%) or low (0.1%) calcium diets during pregnancy. Nonpregnant animals were also randomly assigned to one of the calcium diets. We used a stratified design based on the blood lead concentration at the time of random assignment. This ensured comparable initial blood lead concentrations in the two lead-exposed treatment groups that were fed either 0.1% or 0.5% calcium. During pregnancy, dam body weights were measured twice each week. In addition, blood samples (150 pL) were drawn from a tail vein once each week.

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Section: Resultssupporting

confidence: 84%

Section: Resultsmentioning

confidence: 99%

Effects of lead exposure before pregnancy and dietary calcium during pregnancy on fetal development and lead accumulation.

Han

Pfizenmaier

Garcia

et al. 2000

Environ Health Perspect

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“…Accelerated absorption of dietary lead and decreased elimination of lead from the body, perhaps following the calcium conservation strategies of late pregnancy (17), and release of bone lead may all operate to yield the observed pattern of lead during pregnancy.…”

Section: Discussionmentioning

confidence: 99%

Changes in serial blood lead levels during pregnancy.

Rothenberg

Karchmer

Schnaas

et al. 1994

Environ Health Perspect

107

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The first step in modli lead kinetics during pregnancy includes a description of sequential matenal blood lead (PbB) Cross-sectional studies of groups of women at different stages of pregnancy present conflicting results (1-3), and the design is inadequate to study serial changes of lead during pregnancy. Case studies with serial measurements of PbB in pregnant women are interesting (4-6), but these are usually of women suffering frank lead intoxication.The only detailed work prospectively studying PbB in pregnant women is that of Barltrop (7) A priori exclusion criteria for the study were: 1) younger than 15, older than 42; 2) active diabetes, German measles, hepatitis, or toxoplasmosis, as determined by laboratory test, 3) habitual use of alcohol or drugs, 4) use of prescription medications, 5) hypertension controlled with medication, 6) active psychosis. Women not excluded by these criteria were informed of the purpose of the study and the procedures involved. They read, or were read, a statement of informed consent approved by the institutional review board, and signed it.A total of 532 women passed the exclusion criteria and were enrolled in the study. Of this total, 30 never arrived at the project office for their first or following appointments. One case developed hypoglycemia and 27 developed conditions described by the above exclusion criteria during their pregnancy; 22 spontaneously aborted, and 16 were stillbirths. We will report these data elsewhere. The exclusion of these subjects left 436 participants.Some of the remaining women gave birth to babies meeting the following a priori exclusion criteria, and these 22 pregnancies were also removed from the present data set: 1) birth weight under 2000 g, 2) gestation age under 36 weeks, 3) 5-min Apgar score under 6, 4) multiple birth, and 5) major congenital anomaly. An additional 41 babies suffered from hyperbilirubinemia, high lead level [one baby was born with a cord level of 69 pg/dl (3.33 pmol/l); see Rothenberg et al. (6) for description of this case], minor congenital anomaly, severe infection, birth trauma, asphyxia, respiratory difficulty, or early infant death, and these cases were also excluded from the data set. Table 1 summarizes data on 159 patients who were excluded or who dropped out of the study and compares them to 373 patients retained in the study. Excluded patients were significantly older, had more pregnancies and abortions, and gave birth to lower birth-weight and lower

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“…Hormonal studies (7,9,25,26,27) are not well defined as of yet and more investigation is required. Further research is also needed concerning polar metabolites of vitamin D in neonatal period (32).…”

Section: Speculationmentioning

confidence: 99%

Role of Calcium-Phosphate Ratio of Milk Formulae on Calcium Balance in Low Birth Weight Infants during the First Three Days of Life

Benavent

Doménech

1982

Pediatr Res

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SummaryTwenty-six low birthweight infants with no differences in the neonatal status were allocated into three groups. Group A (10 infants), Group B (8 infants), and C (8 infants) received formulae with 2.4, 1.6, and 4.1 Calcium/Phosphate (Ca/Pi) ratio respectively. Formula C was supplemented with calcium lactate 800 mg/ kg/day, which yielded 12.7 + 0.4 mg of Ca and 0.04 + 0.002 mg of Mg per each 100 mg of salt (mean f S.D.). The osmolality of the C formula before its administration was 361 + 52 mOsm/kg. Balances (mean + S.D.) from the first feeding up to a period of 3 days were obtained. The intestinal product before any feeding contained: Ca, 1.3 + 0.6 mg/kg; Mg, 2.9 2 1.5 mg/kg, and Pi, 1.5 2 2.3 mg/kg. Calcium intake (mg/kg/day) was 89.7 f 13.8 for formula A, 71.1 + 12.5 for formula B, and 156.8 + 19.8 for formula C. Their net retention (mg/kg/day) was 50.8 + 15.9, 39.3 + 12.8 ( P < 0.05), and 105.2 f 21.9 ( P < 0.001) respectively. Net retention of Pi was comparable in the three groups (A, B and C) ranging 24.7-25.7 mg/kg/day. Small variations in intake are finely compensated by parallel urinary excretion (range 6.3-12.8 mg/kg/day).Magnesium absorption did not show differences among the three formulae. The evolution of plasmatic values for magnesium was fairly normal in the three groups. Phosphatemia was significantly ( P < 0.01) lower in group A (lowest Pi containing formula) on the 3rd day. Patients on formula B (smaller Ca content) showed a mean blood calcium of 7.9 mg/dl, which was significantly lower than in the other groups. In two instances, blood calcium was lower than 6.9 mg/dl (Z = 6.32; P < 0.05). Net retention of calcium correlates~positively with Ca/Pi ratio (r = 0.82) and with absolute Ca intake (r = 0.84). Calcium lactate supplementation did not modify acid base equilibrium, lactatemia nor digestive tolerance. SpeculationTo prevent demineralization in the early postnatal period of preterm babies, the net retention of calcium could be improved more effectively by adding a calcium supplement to the formula rather than by decreasing its Pi content, even though both procedures lead to a comparable Ca/Pi quotient.If postnatal growth of the preterm infant parallels that in utero, then calcium intake should be sufficient to achieve a retention equivalent to that provided by the placenta; however, reality has demonstrated that this is a delusion (12,20,29). The reduction in calcium supply after birth leads, apart from early hypocalcemia, to two abnormal conditions recently reevaluated. First, the presence of a late rickets when the birthweight of the very low birthweight infant doubles. Although thisYcondition h a d been classically known, Kulkarni et al. (17) reported a 13% incidence of rickets in babies weighing less of 1.5 kg and receiving 500 IU of vitamin D from the 10th day of life onwards. Second, a reduced calcium supply after birth can lead to a decreased bone mineralization after birth (32). The preterm infant needs 10 days to equal the bone mineral content he had at birth, as estimated by ...

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Calcium metabolism in pregnancy: A review

Cited by 144 publications

References 97 publications

Effects of lead exposure before pregnancy and dietary calcium during pregnancy on fetal development and lead accumulation.

Effects of lead exposure before pregnancy and dietary calcium during pregnancy on fetal development and lead accumulation.

Changes in serial blood lead levels during pregnancy.

Role of Calcium-Phosphate Ratio of Milk Formulae on Calcium Balance in Low Birth Weight Infants during the First Three Days of Life

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