Serum calcium, phosphorus and magnesium levels in pregnant and non-pregnant Nigerians

Serum Calcium and Magnesium Levels in Normal Ghanaian Pregnant Women: A Comparative Cross-Sectional Study

BACKGROUND:

Pregnancy is described as a normal physiologic state associated with various biochemical changes. Magnesium and calcium are essential macronutrients required for foetal growth. Complications associated with their deficiency during normal pregnancy include; low neonatal birth weight, pre-eclampsia, eclampsia and preterm labour. Changes in serum levels of magnesium and calcium in normal pregnancy have not been extensively studied among Ghanaian women.

AIM:

To determine the variation in serum magnesium and calcium levels with gestational age in normal pregnancy in Ghanaian women.

METHODS:

A hospital-based comparative cross-sectional study was conducted among 32 normal non-pregnant women (Group A) and 100 normal pregnant women (Group B) attending the clinic at the Korle-Bu Teaching hospital. The group B pregnant women were further divided into Group B1 (n = 33), Group B2 (n = 37) and Group B3 (n = 30) based on their pregnancy gestation as first, second and third trimester respectively. Blood samples were obtained from the antecubital vein of subjects and total serum calcium, magnesium, protein and albumin were estimated. Data obtained were analysed using SPSS for windows version 20. Analysis of variance (ANOVA) was employed to determine the statistical differences between the groups. A p-value of ≤ 0.05 was considered significant.

RESULTS:

Mean serum total calcium and magnesium in first, second and third trimester normal pregnant women were 2.14 ± 0.16, 2.13 ± 0.44, 2.13 ± 0.35 mmol/L and 0.77 ± 0.11, 0.77 ± 0.16 and 0.76 ± 0.14 mmol/L respectively. Mean serum total calcium and magnesium levels in non-pregnant women were 2.20 ± 0.16 and 0.80 ± 0.10 mmol/L respectively. There was a statistically non-significant difference in serum total calcium and magnesium between non-pregnant and normal pregnant women, with p-values of 0.779 and 0.566 respectively. Mean total serum protein and albumin in first, second and third-trimester normal pregnant women were 68.42 ± 10.37, 70.46 ± 6.84, 66.70 ± 7.83 g/L and 39.92 ± 3.22, 40.75 ± 8.06, 38.26 ± 3.02 g/L respectively. Mean total serum protein and albumin in non-pregnant women were 73.13 ± 7.02 and 42.94 ± 3.03 g/L respectively. Mean total serum protein and albumin levels were lower in pregnant women as compared to non-pregnant women with the difference being significant in the third trimester (p-values of 0.012 and 0.002).

CONCLUSION:

Total serum calcium and magnesium levels in normal pregnancy were non-significantly lower compared to non-pregnant women in Ghana. There was a reduction in total serum protein, and albumin levels during pregnancy with a significant reduction noticed during the third trimester compared to the non-pregnant state.

The Role of Calcium Correction during Normal Pregnancy at Third Trimester in Mosul

OBJECTIVES

To assess calcium status in healthy pregnant women during limited sun exposure time in winter, and to demonstrate the possible effect of serum albumin alterations on serum total calcium level and the role of albumin adjusted calcium concentration.

METHODS

Subjects enrolled in the study included 160 apparently healthy women divided equally into four groups (I - IV), group I was considered as the control group, composed of non-pregnant women. Groups II-IV were composed of pregnant women in the first, second and third trimesters respectively. Semiquantitative urine protein determination and measurement of serum total calcium, ionized calcium, albumin, phosphorous and creatinine with calculation of corrected calcium were performed in all groups. The results were statistically evaluated by standard statistical methods.

RESULTS

There was no significant difference in serum ionized calcium, corrected calcium and phosphorous during pregnancy. However, there was a significant reduction of serum total calcium, albumin and creatinine in pregnant women at second and third trimesters. In each group, a significant positive correlation was observed between total calcium with corrected and ionized calcium.

CONCLUSION

In healthy pregnant women even during limited sun exposure time in winter, there was no need for calcium supplementation in spite of the continuous and progressive reduction of serum measured total calcium during the second and third trimesters due to dilutional hypoalbuminemia. During pregnancy, measured calcium is parallel to both corrected and ionized calcium and since there was no significant difference between measured and corrected calcium, therefore, measured calcium is a useful test in assessing calcium status and suggests the need to establish a reference range for pregnant women.

Is hypotonic dysfunctional labor associated with hypophosphatemia?

OBJECTIVE

The purpose of this study was to determine whether hypotonic dysfunctional labor is associated with hypophosphatemia.

STUDY DESIGN

We conducted a prospective nested case control study of term women who were in active labor. Serum phosphate samples were drawn at admission with active labor and before delivery. Phosphate concentration was compared between control subjects and women with hypotonic, dysfunctional uterine contractions.

RESULTS

Both serum samples were available for 90 women. Hypophosphatemia was documented in 14% of the participants. There was no significant difference in phosphate concentration between the 2 groups either at admission or before delivery. The mean decrease in phosphate concentration between admission and delivery was similar between the 2 cohorts.

CONCLUSION

Although transient hypophosphatemia is found commonly in laboring women, hypotonic dysfunctional contractions are not associated with mild hypophosphatemia.

Hyperparathyroidism and pregnancy: case report and review

In pregnant women with symptomatic hyperparathyroidism, parathyroidectomy should be undertaken during the second trimester. We feel that the woman who is initially diagnosed well into the third trimester should be treated medically unless the hypercalcemia worsens or other complications occur. Since the treatment of asymptomatic hyperparathyroidism itself is controversial, it is even more difficult to define the treatment plan for an asymptomatic pregnant patient who has primary hyperparathyroidism. However, a recent consensus panel recommended that young patients with asymptomatic hyperparathyroidism be treated surgically. Accordingly, we believe that the asymptomatic pregnant patient should also be treated surgically, preferably in the second trimester. Whether a patient is treated medically or surgically in these situations, the pregnancy should be considered high-risk. The neonate should be monitored carefully for signs of hypocalcemia or impending tetany. If the mother is treated medically to term (or if spontaneous or elective abortion occurs), the mother should be monitored for hyperparathyroid crisis postpartum. Sudden worsening of hypercalcemia can result from the loss of the placenta (active placental calcium transport may be somewhat protective) and dehydration. Finally, every effort should be made to make the definitive diagnosis early in pregnancy in order to initiate optimal management. The diagnosis should be suspected during pregnancy if the following conditions exist: appropriate clinical signs or symptoms (especially nephrolithiasis or pancreatitis), hyperemesis beyond the first trimester, history of recurrent spontaneous abortions/stillbirths or neonatal deaths, neonatal hypocalcemia or tetany, or a total serum calcium concentration greater than 10.1 mg/dL (2.52 mmol/L) or 8.8 mg/dL (2.2 mmol/L) during the second or third trimester, respectively.

Rickets in Nigerian children: a consequence of calcium malnutrition

Eleven Nigerian children with clinically and radiologically proven rickets were assessed biochemically. The children had low or low normal concentrations of total and corrected calcium, and elevated plasma alkaline phosphatase (ALP) activity, but normal plasma phosphate concentrations. Their serum 25-hydroxyvitamin D (25-OHD) and 1,25-dihydroxyvitamin D (1,25-(OH)2D) concentrations were not significantly different from those in controls, but the ratio of 1,25-(OH)2D to 25-OHD was significantly greater than that in controls. Parathyroid hormone (PTH) concentrations were greater in rachitic children, and there was a significant correlation between 1,25-(OH)2D and PTH concentrations. Osteocalcin concentrations in rachitic children were not significantly different from those in controls, but they were markedly elevated in the three patients with the highest 1,25-(OH)2D and PTH concentrations. One child, from whom a sample of bone (from a corrective osteotomy) was available for histological examination, showed markedly thickened osteoid seams, characteristic of rickets. All the rachitic children had a calcium intake of less than 150 mg daily. Treatment of these rachitic children with calcium gluconate (1 g/d) led to clinical, radiological, and biochemical healing of rickets. We conclude that rickets in Nigerian children is not due to vitamin D deficiency, but to a lack of calcium. This observation has implications regarding the pathogenesis, treatment, and prevention of rickets/osteomalacia in Nigeria and possibly other African and tropical countries.

Determination of trace and bulk elements in plasma and erythrocytes of healthy pregnant women by PIXE method

Particle Induced X-ray Emission (PIXE) analysis of blood samples from healthy pregnant women was carried out. Elements S, Ca, P, K, Cl, Fe, Zn, Cu, Rb and Br were detected, in red blood cells while S, Ca, P. K, Cl, Fe, Zn, Cu, Ni, Br in the plasma. The concentrations of Ca, K and Br were found to be stable throughout pregnancy, others exhibited significant alterations. The importance of macro- and microelement metabolisms during pregnancy and their role in the intrauterine development is summarized.

Vitamin D nutrition in pregnant Nigerian women at term and their newborn infants

In view of the high incidence of rickets in infants of women practising purdah (the use of veils) in northern Nigeria we conducted a study on plasma calcium, phosphate, and serum 25-hydroxyvitamin D (25 OHD) concentrations in pregnant Nigerian women and in cord blood obtained from the newborns. Plasma calcium, phosphate, and serum 25 OHD concentrations were lower in practising women and their newborns than those not practising purdah and their infants, respectively. The concentrations of 25 OHD in all Nigerian women were greater than those observed in caucasian women in the United Kingdom. These data emphasise the role of exposure to sunshine in regulating serum 25 OHD concentrations and the adverse effect of deliberate exclusion of sunshine and are consistent with previous data indicating hypovitaminosis D in purdah clad women and their newborns in Saudi Arabia. These data do not, however, provide an explanation for the pathogenesis of the high incidence of neonatal rickets and tetany in infants born of purdah clad women as these women have 25 OHD concentrations greater than those in caucasian women in the United Kingdom.

The effects of oral iron supplementation on zinc and magnesium levels during pregnancy

Serial changes in serum zinc and magnesium concentrations have been studied before conception, throughout pregnancy and at 12 weeks postpartum in 15 normal healthy women not receiving iron supplementation, 10 women receiving iron supplementation but otherwise having healthy pregnancies and five insulin-dependent diabetics who also received oral iron. Relative to pre-pregnancy values zinc concentrations progressively decreased throughout pregnancy reaching a nadir at 36 weeks gestation followed by an increase; pre-pregnancy values were achieved by 12 weeks postpartum. Magnesium concentrations also decreased throughout pregnancy reaching a nadir at 32 weeks gestation increasing thereafter again with pre-pregnancy values achieved by 12 weeks postpartum. Iron supplementation in non-diabetic and diabetic women had no significant effect upon the changes in serum concentration of either zinc or magnesium. These results suggest that the decrease in the concentrations of both elements is a normal physiological adjustment to pregnancy and that iron supplementation does not influence these changes.

Calcium metabolism in pregnancy and the perinatal period: a review

Calcium homeostasis is a complex process involving calcium, other involved ions, and three calcitropic hormones, parathyroid hormone, calcitonin, and 1,25-dihydroxyvitamin D3. The principal maternal adjustment during pregnancy is an increasing parathyroid hormone secretion which maintains the serum calcium concentration in the face of a falling albumin level, an expanding extracellular fluid volume, an increasing renal excretion, and placental calcium transfer. The placenta transports calcium ions actively, making the fetus hypercalcemic relative to its mother, which in turn stimulates calcitonin release and perhaps suppresses parathyroid hormone secretion by the fetus. A unique extrarenal system for 1 alpha-hydroxylation of 25-hydroxyvitamin D3 exists in the placenta and/or decidua, providing a source of 1,25-dihydroxyvitamin D3 for the fetus. With the abrupt cessation of the placental source of calcium at birth, the neonate's serum calcium level falls for 24 to 48 hours, then stabilizes and rises slightly. Hyperparathyroidism during pregnancy causes complications in both mother and infant and should usually be treated surgically as soon as diagnosed. Maternal hypoparathyroidism can be treated satisfactorily with high doses of supplemental calcium and vitamin D. Osteopenia accompanying long-term heparin administration may respond to 1,25-dihydroxyvitamin D3 (calcitriol) therapy. Diabetes in pregnancy is associated with disturbed neonatal calcium homeostasis, perhaps due to chronic hypomagnesemia. A possible etiologic role of calcium deficiency in pregnancy-related hypertension has been suggested. Dietary deficiency of calcium and/or vitamin D during gestation may lead to several adverse effects in the newborn infant.

Origins and significance of the increased plasma alkaline phosphatase during normal pregnancy and pre-eclampsia

Total alkaline phosphatase (AP) was measured in maternal plasma, cord plasma and placental extracts in normal and in pre-eclamptic pregnancies. Total plasma AP was significantly elevated during the last two trimesters in normal and pre-eclamptic pregnancies, but contrary to previous reports, both placental and bone AP isoenzymes contributed to the significant elevation of total AP in both types of pregnancy. There was no placental AP isoenzyme in cord plasma but total cord plasma AP was higher in normotensive pregnancies than in pre-eclamptic pregnancies. Total AP concentration in placental tissue was higher in normotensive pregnancies than in pre-eclamptic pregnancies. A correlation was established between placental weights and maternal circulating placental AP.

Calcium metabolism in normal pregnancy: a longitudinal study

Total and ionic calcium, magnesium, phosphorus, albumin, and immunoreactive parathyroid hormone (iPTH) and calcitonin (iCT) were measured in serum or plasma from 30 women throughout pregnancy (beginning before 12 weeks' gestation) and the puerperium. Total calcium levels declined during gestation, paralleling a progressive fall in albumin concentration, whereas ionic calcium values declined only very slightly. Although iPTH levels in early pregnancy were lower than postpartum values (suggesting that iPTH may decline initially following conception), the major portion of gestation was characterized by progressively increasing concentrations which at term averaged 53% above early pregnancy levels and 33% above puerperal values. Thus, the principal adjustment during pregnancy is "physiologic hyperparathyroidism" which acts to preserve maternal homeostasis by maintaining the concentration of calcium ions in extracellular fluid in the presence of expanding fluid volume, increased renal function, and placental transfer. iCT levels were not affected consistently by pregnancy and exhibited highly variable patterns; half of the subjects demonstrated an increase during the first and second trimesters and then a decline in the third trimester and the remaining half was equally divided between those with no change and those with progressively falling levels.