Hypocalciuria in preeclampsia

Causal pathways in preeclampsia: a Mendelian randomization study in European populations

Purpose

Our study utilizes Mendelian Randomization (MR) to explore the causal relationships between a range of risk factors and preeclampsia, a major contributor to maternal and perinatal morbidity and mortality.

Methods

Employing the Inverse Variance Weighting (IVW) approach, we conducted a comprehensive multi-exposure MR study analyzing genetic variants linked to 25 risk factors including metabolic disorders, circulating lipid levels, immune and inflammatory responses, lifestyle choices, and bone metabolism. We applied rigorous statistical techniques such as sensitivity analyses, Cochran's Q test, MR Egger regression, funnel plots, and leave-one-out sensitivity analysis to address potential biases like pleiotropy and population stratification.

Results

Our analysis included 267,242 individuals, focusing on European ancestries and involving 2,355 patients with preeclampsia. We identified strong genetic associations linking increased preeclampsia risk with factors such as hyperthyroidism, BMI, type 2 diabetes, and elevated serum uric acid levels. Conversely, no significant causal links were found with gestational diabetes, total cholesterol, sleep duration, and bone mineral density, suggesting areas for further investigation. A notable finding was the causal relationship between systemic lupus erythematosus and increased preeclampsia risk, highlighting the significant role of immune and inflammatory responses.

Conclusion

This extensive MR study sheds light on the complex etiology of preeclampsia, underscoring the causal impact of specific metabolic, lipid, immune, lifestyle, and bone metabolism factors. Our findings advocate for a multidimensional approach to better understand and manage preeclampsia, paving the way for future research to develop targeted preventive and therapeutic strategies.

Approach to Pregnancy in Patients With Lupus Nephritis

Active lupus nephritis (LN) in pregnancy is strongly associated with poor maternal and fetal outcomes and, therefore, has implications on the planning, timing, and management. Prepregnancy evaluation is essential for all LN patients with childbearing potential to ensure pregnancies proceed in a safe and timely manner. Both maternal and fetal risks are communicated to patient during the evaluation. Stratification into different risk profile groups is then made based on disease activity and organ impairment severity. Patients with LN are generally divided into 3 main groups. Patients with LN who become pregnant receive treatments that are nonteratogenic and optimal for fetal and maternal outcomes. Throughout the pregnancy period, these patients are monitored closely under surveillance by a multidisciplinary team of clinicians. The management of patients with LN in pregnancy can be challenging both diagnostically (distinguishing LN from pre-eclampsia and determining the role and timing of kidney biopsy) and therapeutically (LN flares during pregnancy and managing a newly diagnosed LN during pregnancy).

Impact of vitamin D binding protein (GC) and vitamin D receptor (VDR) gene polymorphism on the risk of developing preeclampsia

OBJECTIVE

Preeclampsia is a multifactorial disease characterized by high blood pressure and protein in the urine. In this study, we investigated the association of vitamin D binding protein (GC) and vitamin D receptor (VDR) gene polymorphism with the risk of developing preeclampsia.

METHODS

25-hydroxyvitamin D was measured using High-performance Liquid Chromatography. Vitamin D binding protein and vitamin D receptor gene polymorphisms were determined by polymerase chain reaction-restriction fragment length polymorphism.

RESULTS

The control subjects have significant higher level of 25-hydroxyvitamin D (33.5 ± 1.194 ng/mL) relative to patients (23.97 ± 1.604 ng/mL) (p < 0.05). Vitamin D receptor rs1544410 and rs2228570 dominant model (GA + AA; TC + CC) showed significant higher risk of developing Preeclampsia (OR = 4.11, 95% CI = 0.62-27.09, p < 0.01; OR = 3.58, 95%CI = 0.78-16.38, p < 0.001 respectively). Similarly, vitamin D binding protein rs7041 and rs4588, dominant model (TG + GG; CA + AA) showed higher risk of preeclampsia development compared to control people (OR = 1.69, 95%CI = 0.35-8.19, p < 0.05; OR = 1.06, 95%CI = 0.25-4.44, p < 0.05 respectively). AA genotype of rs4588 of GC gene was significantly associated with 25-hydroxyvitamin D level in serum relative to CC and CA (p < 0.05).

CONCLUSION

From our study, we can conclude that a low level of 25-hydroxyvitamin D, GC (rs1544410 and rs2228570), and VDR (rs4588 and rs7041) gene polymorphism is linked with an increased risk of developing preeclampsia.

Serum lncRNAs in early pregnancy as potential biomarkers for the prediction of pregnancy-induced hypertension, including preeclampsia

Long noncoding RNAs (lncRNAs) are key mediators of biological regulation with diagnostic value as disease biomarkers. We explored serum lncRNA levels in early pregnancy as potential biomarkers of pregnancy-induced hypertension (PIH), including gestational hypertension (GH) and preeclampsia (PE). We performed a two-phase nested case-control study in pregnant women before 20 weeks’ gestation (before clinical diagnosis). The screening phase assessed lncRNA expression profiles with a human lncRNA microarray in 5 pairs of serum samples (5 PE patients and 5 matched controls). The second phase validated levels of 8 candidate lncRNAs selected via the random walk method by quantitative real-time polymerase chain reaction (qRT-PCR). Serum levels of the 8 lncRNAs were markedly increased in women with PIH compared with matched normotensive pregnant (NP) women (p < 0.001), consistent with the microarray results. In addition, 7 candidate lncRNAs were correlated with PIH severity. Logistic regression analysis revealed that serum levels of ENST00000527727 (odds ratio [OR], 1.113; 95% confidence interval [CI], 1.024–1.209; p = 0.0113) and ENST00000415029 (OR, 1.126; 95% CI, 1.000–1.267; p = 0.0496) were associated with adverse pregnancy outcomes, such as fetal growth restriction (FGR) and placenta accreta of PIH. Nine pathways associated with the candidate lncRNAs had confirmed associations with PIH.

Secondary hyperparathyroidism is associated with postpartum blood pressure in preeclamptic women and normal pregnancies

BACKGROUND

Preeclampsia has been associated with features of secondary hyperparathyroidism. In this study, we examine the relationships of calcium metabolism with blood pressure (BP) in preeclamptic women and in a control group of normal (NORM) pregnancies in the postpartum.

METHODS

Sixty-three consecutive preeclamptic women (age 35 ± 6 years) were studied 4 weeks after delivery. We collected clinical and lab information on pregnancy and neonates and measured plasma and urinary calcium and phosphate, plasma parathyroid hormone (PTH) and 25-hydroxy vitamin D [25(OH)D], and performed 24-h ambulatory BP monitoring. BP and calcium metabolism of 51 preeclamptic were compared with 17 NORM pregnant women that matched for age, race, and postpartum BMI.

RESULTS

25(OH)D deficiency (<10 ng/ml) was found in 3% of preeclamptic women, insufficiency (10-30 ng/ml) in 67%, and NORM values (31-100 ng/ml) in the remaining 30%. Elevated plasma PTH (≥79 pg/ml) was found in 24% of preeclamptic women who had 25(OH)D plasma levels of 21.4 ± 8.3 ng/ml. In these women, PTH levels was independently associated with 24-h SBP and DBP and daytime and night-time DBP. Prevalence of nondippers and reverse dippers was elevated (75% and 33%, respectively). No associations between calcium metabolism and neonates' characteristics of preeclamptic women were observed. Prevalence of vitamin D deficiency and insufficiency and of elevated plasma PTH levels were comparable in matched groups. Considering preeclamptic women and matched controls as a whole group, office SBP and DBP levels were associated with PTH independently of preeclampsia and other confounders.

CONCLUSION

Features of secondary hyperparathyroidism are common in the postpartum. Preeclampsia and increased PTH levels were both independent factors associated with increased BP after delivery, and both might affect the future cardiovascular risk of these women.

Inorganic Phosphate in the Pathogenesis of Pregnancy-Related Complications

Inorganic phosphate (P_i) is an essential nutrient that fulfills critical roles in human health. It enables skeletal ossification, supports cellular structure and organelle function, and serves key biochemical roles in energetics and molecular signaling. P_i homeostasis is modulated through diet, intestinal uptake, renal reabsorption, and mobilization of stores in bone and extracellular compartments. Disrupted P_i homeostasis is associated with phosphate wasting, mineral and bone disorders, and vascular calcification. Mechanisms of Pi homeostasis in pregnancy remain incompletely understood. The study presented herein examined biological fluid Pi characteristics over the course of gestation. Correlations with gestation age, pregnancy number, preterm birth, preeclampsia, diabetes mellitus, and placental calcification were evaluated during the last trimester. The results support that maternal urinary P_i levels increased during the third trimester of pregnancy. Reduced levels were observed with previous pregnancy. Amniotic fluid P_i levels decreased with gestation while low second trimester levels associated with preterm birth. No significant difference in urinary P_i levels was observed between preeclampsia and controls (8.50 ± 2.74 vs. 11.52 ± 2.90 mmol/L). Moreover, increased maternal urinary P_i was associated with preexisting diabetes mellitus in preeclampsia. Potential confounding factors in this study are maternal age at delivery and body mass index (BMI)—information which we do not have access to for this cohort. In conclusion, P_i levels provide clinical information regarding the pathogenesis of pregnancy-related complications, supporting that phosphate should be examined more closely and in larger populations.

Serum magnesium and calcium in preeclampsia: a comparative study at the Korle-Bu Teaching Hospital, Ghana

Background

A large percentage (16% of maternal mortality in developed countries, compared to 9% in developing countries), is due to hypertensive disorders in pregnancy. The etiology of preeclampsia remains unknown, with poorly understood pathophysiology. Magnesium and calcium play an important role in vascular smooth muscle function and therefore a possible role in the development of preeclampsia.

Aim

We aimed to compare serum magnesium and total calcium levels of preeclamptic and normal pregnant women at the Korle-Bu Teaching Hospital in Ghana.

Patients and methods

A comparative cross-sectional study involving 30 normal pregnant and 30 preeclamptic women with >30 weeks gestation and aged 18–35 years, was conducted at the Korle-Bu Teaching Hospital. Magnesium and calcium were determined using a flame atomic absorption spectrometer.

Results

Mean serum magnesium and total calcium levels in preeclamptic women were 0.70±0.15 and 2.13±0.30 mmol/L, respectively. Mean serum magnesium and total calcium levels in normal pregnant women were 0.76±0.14 and 2.13±0.35 mmol/L, respectively. There was a statistically nonsignificant difference in serum magnesium and total calcium in preeclamptic women compared to normal pregnant women, with p-values of 0.092 and 0.972, respectively.

Conclusion

Serum magnesium and total calcium, therefore, seem not to differ in preeclamptic women compared to normal pregnant women in Ghana.

[Can we prevent preeclampsia?]

Preeclampsia (PE), a specific complication of pregnancy, is one of the most frequent causes of maternal and fetal morbidity and mortality in the world. Recently, PE risk calculation algorithms allowing early detection of PE in the first trimester of pregnancy have been described. The aim of early detection would be to rapidly introduce an effective preventive treatment. The aim of our work is to study the different preventive treatments through the literature. Aspirin has some efficiency and reduces the risk of PE from 10 to 24%. It is most effective when the dose exceeds 75mg and when introduced before 16 gestational age. Early introduction of aspirin mainly prevents severe and preterm PE. Low molecular weight heparin (LMWH) and vitamin D appear to be promising therapy for PE but further research is required. Calcium administered at 1g/day reduces the risk of PE especially to patients with low baseline calcium intake. A low dose of calcium could also reduce the risk of PE but this must be confirmed. Other preventive measures (antioxidants, nitric oxide, progesterone, rest, exercise) do not reduce the incidence of PE.

Vitamin D and the Promotion of Long-Term Metabolic Health from a Programming Perspective

Studies linking vitamin D and long-term metabolic health have generated much debate. Recommendations for the intake of vitamin D by the general public and by the health care professionals have been complicated by a number of inconsistencies in the literature. These caveats relate to the methodological approaches, differences in the populations (and the species) of study, and the definitions used for thresholds of vitamin D status. This review addresses current evidence available for assessing the potential programming of long-term metabolic health of offspring by maternal vitamin D status in pregnancy. It summarizes knowledge on the early origins of metabolic health and analyzes evidence for an association between the vitamin D status in pregnancy and maternal and fetal health status. In addition, we analyze the link between the regulation of inflammation and the vitamin D status in the general population to inform on the general mechanisms through which early vitamin D might affect the programming of long-term health. The evidence suggests an association between the vitamin D status in early life and the programming of long-term health. However, to the best of our knowledge, the current finding is insufficient to draw a final conclusion for evidence-based preventive actions. The data warrant replication in prospective studies and additional research substantiating the causal factors and pathways.

Vitamin D and Inflammatory Cytokines in Healthy and Preeclamptic Pregnancies

Preeclampsia is a pregnancy disease characterized by hypertension and proteinuria. Among several disorders, the imbalance of inflammatory cytokines and the alteration of vitamin D metabolism have been reported in preeclampsia. The effects of calcitriol upon inflammatory cytokines has been demonstrated. In healthy pregnant women there is a shift toward a Th2 cytokine profile, which is necessary for an adequate pregnancy outcome. As compared with normal pregnancy, high pro-inflammatory and low anti-inflammatory cytokine levels have been observed in preeclamptic women. Preeclampsia has been associated with low calcitriol levels and vitamin D deficiency is correlated with a higher risk of the development of this disease. It has been demonstrated that placenta is a source as well as the target of calcitriol and cytokines and placental dysfunction has been associated with preeclampsia. Therefore, the present manuscript includes a review about serum calcitriol levels in non-pregnant, pregnant, and preeclamptic women as well as a review on the fetoplacental vitamin D metabolism in healthy and preeclamptic pregnancies. In addition, circulating and fetoplacental inflammatory cytokines in healthy and preeclamptic pregnancies are reviewed. Finally, the effects of calcitriol upon placental pro-inflammatory cytokines are also explored. In conclusion, maternal and placental calcitriol levels are low in preeclampsia which may explain, at least in part, high pro-inflammatory cytokine levels in this disease.

[Vitamin D deficiency in pregnancy and its impact on the fetus, the newborn and in childhood]

OBJECTIVE

Vitamin D deficiency (VDD) in pregnant women and their children is an important health problem with severe consequences for the health of both. Thus, the objectives of this review were to reassess the magnitude and consequences of VDD during pregnancy, lactation and infancy, associated risk factors, prevention methods, and to explore epigenetic mechanisms in early fetal life capable of explaining many of the non-skeletal benefits of vitamin D (ViD).

DATA SOURCE

Original and review articles, and consensus documents with elevated level of evidence for VDD-related clinical decisions on the health of pregnant women and their children, as well as articles on the influence of ViD on epigenetic mechanisms of fetal programming of chronic diseases in adulthood were selected among articles published on PubMed over the last 20 years, using the search term VitD status, in combination with Pregnancy, Offspring health, Child outcomes, and Programming.

DATA SYNTHESIS

The following items were analyzed: ViD physiology and metabolism, risk factors for VDD and implications in pregnancy, lactation and infancy, concentration cutoff to define VDD, the variability of methods for VDD detection, recommendations on ViD replacement in pregnant women, the newborn and the child, and the epigenetic influence of ViD.

CONCLUSIONS

VDD is a common condition among high-risk pregnant women and their children. The routine monitoring of serum 25(OH)D3 levels in antenatal period is mandatory. Early preventive measures should be taken at the slightest suspicion of VDD in pregnant women, to reduce morbidity during pregnancy and lactation, as well as its subsequent impact on the fetus, the newborn and the child.

A prospective study for the prediction of preeclampsia with urinary calcium level

OBJECTIVES

To assess the efficacy of calciuria as a diagnostic test for the prediction of preeclampsia, and also to determine the changes in urinary excretion of calcium in preeclampsia and normotensive women.

METHODS

A prospective study was conducted on 60 primi mothers in the age group of 20-30 years, and all were enrolled at 16 weeks of gestation with clinical follow up by 4 weeks and 24 h urinary calcium and creatinine estimation. Ten mothers developed preeclampsia (study groups) and fifty remained normotensive (control groups). By means of Receiver-operator curve, a cut-off level of urinary calcium in 24 h was chosen for predicting preeclampsia.

RESULTS

Preeclamptic women excreted significantly less total urine calcium (87.0 ± 3.59 mg/24 h) than normotensive women (303.68 ± 17.699 mg/24 h) (p < 0.0001) at 40 weeks of gestation. Urinary calcium and calcium/creatinine (Ca:Cr) ratio decreases progressively from 28 weeks to 40 weeks in the study group when compared to normotensive group.

CONCLUSIONS

Preeclamptic women excrete less calcium than normotensive women. This parameter would predict preeclampsia earlier in pregnancy.

[Vitamin D and pregnancy]

Vitamin D plays a key role in calcium-phosphorus homeostasis and bone metabolism, but it is also involved in numerous others tissues. Vitamin D deficiency among pregnant women is frequent in many populations over the world. It is associated with an increased risk of preeclampsia, gestational diabetes mellitus, and caesarean section. Consequences in newborns are low birth weight, neonatal rickets, a risk of neonatal hypocalcemia, asthma and/or type 1 diabetes. Therefore, prevention of vitamin D deficiency among pregnant women is essential. The currently recommended supplementation amount of vitamin D is not sufficient to maintain a value of 25 hydroxy vitamin D above 30 ng/ml, during pregnancy. Randomized controlled trials during pregnancy are necessary to evaluate the amount of vitamin D sufficient to avoid the consequences of vitamin D deficiency.

The concentrations of markers of bone turnover in normal pregnancy and preeclampsia

BACKGROUND

The purpose of our study was to investigate the concentrations of markers of bone turnover in normal pregnancy and preeclampsia.

MATERIAL AND METHODS

Forty-five pregnant patients with preeclampsia, 78 healthy pregnant women (26 in first, 26 in the second, and 26 in third trimester of pregnancy), and 20 nonpregnant women were included in the study. Serum concentrations of osteoprotegrin (OPG), receptor activator of nuclear factor kappa B ligand (sRANKL), and the markers of bone turnover, osteocalcin and CrossLaps-degradation products of type I collagen, were determined using the ELISA method. Statistical analysis was performed using Mann-Whitney U-test.

RESULTS

The concentrations of sRANKL and OPG were significantly higher in the second trimester of normal pregnancy when compared to the first and the third trimesters and to nonpregnant controls. The concentrations of osteocalcin were significantly higher in the first trimester of physiological pregnancy in comparison with nonpregnant women and with second and third trimesters of pregnancy. The concentrations of CrossLaps were significantly higher in the second trimester of normal pregnancy when compared to the first and third trimester. In preeclampsia, the sera concentrations of osteocalcin and CrossLaps were significantly higher when compared to the third trimester of normal pregnancy.

CONCLUSION

The results suggest that the bone formation is increased in the first trimester, whereas the bone resorption is increased in the second trimester of normal pregnancy. Furthermore, the results suggest that the bone turnover is increased in patients with preeclampsia when compared to healthy normotensive pregnant women.

First trimester vitamin D, vitamin D binding protein, and subsequent preeclampsia

Previous studies report an association between vitamin D deficiency and hypertension, including the pregnancy-specific disorder preeclampsia. Circulating vitamin D is almost entirely bound to vitamin D binding protein, which increases 2-fold during pregnancy and previous studies have not examined vitamin D binding protein or free vitamin D levels. We performed a nested case-control study within the Massachusetts General Hospital Obstetric Maternal Study, measuring first trimester total 25-hydroxyvitamin D (25[OH]D) and vitamin D binding protein and calculating free 25(OH)D levels. We compared these levels from pregnancies complicated by subsequent preeclampsia (cases, n=39) with those from normotensive pregnancies (controls, n=131). First trimester total 25(OH)D levels were similar in cases and controls (27.4±1.9 versus 28.8±0.80 ng/mL; P=0.435). Despite an association between higher first trimester blood pressures and subsequent preeclampsia, first trimester total 25(OH)D was not associated with first trimester systolic (r=0.11; P=0.16) or diastolic blood pressures (r=0.03; P=0.72). Although there was a trend toward increased risk of preeclampsia with 25(OH)D levels <15 ng/mL (odds ratio: 2.5 [95% CI: 0.89 to 6.90]), this was attenuated after adjustment for body mass index and other covariates (odds ratio: 1.35 [95% CI: 0.40 to 4.50]). First trimester vitamin D binding protein and free 25(OH)D levels were similar in cases and controls and were not associated with first trimester blood pressures. These data suggest that first trimester total and free 25(OH)D levels are not independently associated with first trimester blood pressure or subsequent preeclampsia.

Implications of vitamin D deficiency in pregnancy and lactation

Vitamin D is an essential fat soluble vitamin and a key modulator of calcium metabolism in children and adults. Because calcium demands increase in the third trimester of pregnancy, vitamin D status becomes crucial for maternal health, fetal skeletal growth, and optimal maternal and fetal outcomes. Vitamin D deficiency is common in pregnant women (5-50%) and in breastfed infants (10-56%), despite the widespread use of prenatal vitamins, because these are inadequate to maintain normal vitamin D levels (>or=32 ng/mL). Adverse health outcomes such as preeclampsia, low birthweight, neonatal hypocalcemia, poor postnatal growth, bone fragility, and increased incidence of autoimmune diseases have been linked to low vitamin D levels during pregnancy and infancy. Studies are underway to establish the recommended daily doses of vitamin D in pregnant women. This review discusses vitamin D metabolism and the implications of vitamin D deficiency in pregnancy and lactation.

Urinary calcium and magnesium excretion relates to increase in blood pressure during pregnancy

OBJECTIVE

Pregnancy-induced hypertension and preeclampsia are serious clinical manifestations during late pregnancy and the cause for increased maternal and foetal morbidity and mortality. The pathogenesis is unknown but experience from treatment schemes suggests that minerals may be of importance. Mineral homeostasis is influenced by acid-base conditions. The aim of the study was to elucidate the relation between acid-base balance, urinary mineral excretion and blood pressure during pregnancy.

DESIGN

A prospective observational study of a general population.

MATERIALS AND METHODS

The study was performed at the Midwife Health Center in Borås, Sweden, where practically all pregnant subjects in the catchment area are registered. First time pregnant subjects (n = 123) were voluntarily recruited without exclusion criteria. A 24 h urine sample was collected at pregnancy week 12 and analyzed for creatinine, calcium, magnesium, and urea as a proxy for acid conditions. Blood pressure was recorded every 2-3 weeks until delivery.

RESULTS

There was a relation between the excretion of urea and calcium and magnesium at week 12. A blood pressure increase was found after pregnancy week 30 but only among subjects who had a high excretion of calcium and magnesium at week 12.

CONCLUSIONS

If an increase in blood pressure during the later part of pregnancy a risk indicator for preeclampsia, the results suggest that an excessive secretion of calcium leading to a functional deficit might be a risk indicator for gestational hypertension and preeclampsia. Intervention experiments are required to assess this hypothesis.

Effects of calcium supplementation on uteroplacental and fetoplacental blood flow in low-calcium-intake mothers: a randomized controlled trial

OBJECTIVE

We postulated that calcium supplementation of calcium-deficient pregnant women would lower vascular resistance in uteroplacental and fetoplacental circulations.

STUDY DESIGN

Pulsatility index (PI) and resistance index (RI) (uterine and umbilical arteries) and presence of bilateral uterine artery diastolic notching were assessed by Doppler ultrasound between 20-36 weeks' gestation in 510 healthy, nulliparous Argentinean women with deficient calcium intake in a randomized, placebo-controlled, double-blinded trial.

RESULTS

Average umbilical and uterine artery RI and PI tended to be lower in the supplemented group at each study week. Differences became statistically significant for umbilical artery RI and PI from 32 and 36 weeks, respectively. Estimated probabilities of bilateral uterine artery diastolic notching trended toward lower values in calcium-supplemented women.

CONCLUSION

Calcium supplementation of pregnant women with deficient calcium intake may affect uteroplacental and fetoplacental blood flow by preserving the vasodilation of normal gestation.

Use of 24-hour urinary protein and calcium for prediction of preeclampsia

OBJECTIVE

To assess the efficacy of 24-hour urinary protein and calcium for the prediction of preeclampsia.

MATERIALS AND METHODS

Two hundred normotensive women at 20-28 weeks' gestation were enrolled in the study. All women were asked to collect a 24-hour urine sample. Urinary protein and calcium were measured and expressed as milligrams per 24 hours. Sensitivity, specificity and predictive values were calculated for each test, and cutoff values were calculated using receiver operating characteristic curves.

RESULTS

Twenty-one of the 200 women developed preeclampsia, including eight who developed severe preeclampsia and 13 who developed mild preeclampsia. Compared with the normotensive women (n = 179), the hypertensive patients (n = 21) had significantly lower urinary calcium excretion (167.23 +/- 80.63 mg vs. 277.43 +/- 60.38 mg) and higher proteinuria (351.14 +/- 41.58 mg vs. 296.33 +/- 30.03 mg).

CONCLUSION

A decrease in 24-hour urinary calcium and increase in protein between 20-28 weeks' gestation are risk factors for preeclampsia.

Vaso-active factors in pregnancy

Pregnancy results in profound physiological changes in the cardiovascular system, yet these changes are completely reversible. It is apparent that vaso-active factors, some as yet probably unidentified, which act as humoral or local autocrine or paracrine regulators of vasular resistance, play a major role in these cardio-vascular changes. This role may be heightened in pregnancy when there has to be a large increase in blood flow to the uterus and placenta while maintaining adequate flow to other vascular beds. Our knowledge of the mechanisms of action of these vaso-active factors and their interactions with each other still remains incomplete. Alterations in synthesis and action of these vaso-active factors may occur in pregnancies associated with pregnancy-induced hypertension, pre-eclampsia or intra-uterine growth retardation. Investigation of such alterations may help to elucidate the roles of vaso-active factors in both normal and pathological situations. The gestational hormones oestrogen and progesterone, are obviously prime candidates as overall regulators of the cardiovascular changes of pregnancy and as agents which alter the synthesis or action of other vaso-active factors. Currently, much attention is being focused on the role of local autocrine or paracrine vaso-active factors which may be produced by the endothelium or by the underlying vascular smooth muscle cells and alterations in their production or action in the hyptertensive disorders of pregnancy. The endothelium forms the largest endocrine organ within the body and so its importance in the mediation of vascular events should not be under-estimated. The principal objective of this review is to examine the roles of these many autocrine and paracrine vaso-active factors during pregnancy and their relation with the overall regulation of the vascular system. Changes which may occur and be involved in the aetiology of pre-eclampsia and growth retardation will also be examined.

Decreased fractional urinary calcium excretion and serum 1,25-dihydroxyvitamin D and IGF-I levels in preeclampsia

During preeclampsia several alterations of calcium metabolism have been described, the most common of them is hypocalciuria, which pathophysiology is still unclear. In order to assess the contribution of calciotropic hormones to urinary calcium excretion, a cross-sectional study was done including 26 preeclamptic Mexican women (PE group) and 26 normotensive control pregnant women (NT group). Total and fractional urinary calcium excretion were significantly lower (P<0.0001) in the PE group than in the NT group (82+/-7 versus 171+/-7 mg/24h and 0.62+/-0.38 versus 1.38+/-0.71%, respectively), without significant differences in creatinine clearance, urinary sodium excretion and phosphate tubular reabsorption. In addition, serum 1,25-(OH)(2)D and IGF-I levels were significantly (P<0.05) lower in the PE than in NT group (43+/-9 versus 50+/-9 pg/mL and 195+/-67 versus 293+/-105 ng/mL, respectively), without significant differences in serum PTH levels. In the NT group, association analysis showed that total and fractional urinary calcium excretions positively correlated with serum levels of 1,25-(OH)(2)D (P<0.01) and IGF-I (P<0.001). In the PE group, total urinary calcium excretion positively correlated only with serum 1,25-(OH)(2)D (P<0.05). In conclusion, the results obtained in this study confirm that PE is associated with hypocalciuria and suggest that 1,25-(OH)(2)D and/or IGF-I may be involved in the regulation of urinary calcium excretion.

Maternal cigarette smoking and the risk of pregnancy-induced hypertension and eclampsia

BACKGROUND

Although previous studies have found that maternal smoking decreases the risk of pregnancy-induced hypertension (PIH), the difference of this effect between primiparous and multiparous women has not been well studied and the results of the exposure-response relationships between maternal smoking and PIH are inconsistent. No previous study has specifically examined the relationship between maternal smoking and eclampsia.

METHODS

We analysed data from a population-based retrospective cohort study of 3 153 944 singleton pregnancies in the US. The data were derived from the national linked birth/infant mortality database for 1998. Multiple logistic regressions were used to describe the relationship between cigarette smoking and PIH and eclampsia.

RESULTS

The adjusted odds ratios (ORs) [95% confidence intervals (95% CIs)] for PIH were 0.80 (0.77-0.83) for primiparous women and 0.81 (0.78-0.83) for multiparous women among smokers compared with non-smokers. The corresponding adjusted ORs (95% CIs) for eclampsia were 0.74 (0.66-0.82) and 0.75 (0.68-0.83), respectively. For PIH, the adjusted OR (95% CI) for smokers vs non-smokers were 0.82 (0.79-0.86), 0.81 (0.78-0.83), 0.80 (0.77-0.83), and 0.88 (0.79-0.98), respectively, for 1-5, 6-10, 11-20, and >20 cigarettes per day (test for trend: P = 0.86). The corresponding figures for eclampsia were 0.85 (0.75-0.95), 0.74 (0.66-0.82), 0.68 (0.58-0.78), and 0.73 (0.49-1.04), respectively (test for trend: P = 0.02).

CONCLUSION

Maternal cigarette smoking decreases the risk of PIH and eclampsia, with a significant inverse exposure-response relationship apparent for eclampsia.

Calciuria and preeclampsia: a case-control study

OBJECTIVE

The aim of this study was to compare calciuria of preeclamptic cases to normotensive controls among pregnant women hospitalized in the French West Indies obstetrics department.

STUDY DESIGN

This case-control study included 47 preeclamptic women and 50 controls. The main outcome was 24h urinary calcium excretion rate. Serum levels of creatinine, calcium and uric acid were also analyzed. A logistic regression analysis has been performed to investigate the relationship between hypocalciuria and preeclampsia after having taken into account prognostic preeclampsia factors and pertinent clinical criteria.

RESULTS

Women with preeclampsia had significantly lower calciuria than normotensive patients (1.5 mmol/24h+/-1.0 versus 6.0 mmol/24h+/-4.2, p=0.0001). After taking into account gestational age at hospitalization, body mass index and nulliparity, hypocalciuria was significantly associated with preeclampsia (ORa=21.74; 95% CI, 6.9-66.7). The diagnosis value of a calciuria less than 2.1 mmol/24h is interesting because of its negative predictive value (97%), but its positive predictive value is weak (42%).

CONCLUSION

In our population, preeclamptic women had a calciuria significantly lower than controls.

A prediction model for superimposed preeclampsia in women with chronic hypertension during pregnancy

OBJECTIVE

Women with chronic hypertension are at increased risk for superimposed preeclampsia. We developed a prediction algorithm for superimposed preeclampsia using clinical and laboratory information that were measured early in pregnancy.

STUDY DESIGN

A secondary analysis of data that were collected from 110 women with chronic hypertension who were enrolled in a trial of calcium supplementation was performed. Blood pressure, the renin-angiotensin system, and calcium metabolism were assessed at 12, 20, 28, and 36 weeks of gestation and 6 weeks after delivery. Multivariable logistic regression was used to develop the predictive model.

RESULTS

Thirty-seven women had superimposed preeclampsia. The final model included systolic blood pressure, serum uric acid, and plasma renin activity, which were all measured at 20 weeks of gestation. Women with high systolic blood pressure (>140 mm Hg), elevated uric acid (>3.6 mg/dL), and low plasma renin activity (<4 ng/mL/hr) had an 86% probability of having superimposed preeclampsia. Women with 2 risk factors had a 62% probability of superimposed preeclampsia, and women with only 1 risk factor had a 30% to 40% probability of superimposed preeclampsia.

CONCLUSION

We developed a prediction algorithm that can be validated in future studies for superimposed preeclampsia for women with chronic hypertension.

Seasonal Variation in Preeclampsia Based on Timing of Conception

OBJECTIVE

Studies have suggested that the incidence of preeclampsia may be partially dependent on the month or season of delivery. We sought to evaluate whether preeclampsia occurs seasonally in our population and whether the timing of conception or delivery is more strongly associated with risk.

METHODS

Between January 1995 and August 2003, we identified 142 primiparous women with singleton pregnancies who met the American College of Obstetricians and Gynecologists' definition for preeclampsia and compared them with 7,762 primiparous control deliveries. We analyzed rates of preeclampsia by individual month and 3-month seasonal blocks based on conception and delivery. Data were analyzed with the chi2 test, and logistic regression and odds ratios were calculated where appropriate.

RESULTS

Preeclampsia occurred in 1.8% of singleton primiparous gestations (142/7,904). Cases were younger than controls (26.5 +/- 5.6 versus 28.0 +/- 0 6.0 years, P < .003), of similar race (97% white versus 96% white, P = .69), and equally likely to have a female child (45% versus 48%, P = .41). We found no significant association of month (logistic regression P = .20) of delivery with the risk of preeclampsia. There was a significant association of month (P = .003) of conception with risk of preeclampsia. Conception during the summer months had the highest risk (incidence 2.3%; odds ratio 1.7; 95% confidence limits 1.06, 2.75) compared with spring (incidence 1.4%). Fall (1.7%) and winter (1.6%) conceptions were associated with intermediate rates of preeclampsia.

CONCLUSION

We identified a seasonal variation in preeclampsia that appears to be more strongly related to timing of conception than to the timing of delivery. The highest incidence of preeclampsia was associated with conception in the summer months.

LEVEL OF EVIDENCE

II-2.

Prediction of preeclampsia: can it be achieved?

In this review, the various biochemical tests that have been proposed for the prediction of preeclampsia are described and evaluated. Placenta hormone markers do not predict future disease. They denounce the early placental changes that are part of the evolving disease and only predict the imminent of preeclamptic syndrome. This explains why tests are better predictors when preeclampsia supervenes shortly, and why screening in the first trimester is unlikely to work as well as in the second trimester. The use of multiple markers in the screening should reflect different aspects of the disease process and could increase the specificity and sensitivity of the screening and work on different etiologic factors. The possible use of second-trimester biochemical screening to predict the risk of preeclampsia remains to be investigated in the high-risk population.

TARGET AUDIENCE

Obstetricians & Gynecologists, Family Physicians

LEARNING OBJECTIVES

After completion of this article, the reader should be able to list the various theories on the etiology of preeclampsia, to relate the various risk factors for the development of preeclampsia, and to describe the various screening tests for preeclampsia.

Nutritional interventions during pregnancy for the prevention or treatment of maternal morbidity and preterm delivery: an overview of randomized controlled trials

This overview assesses the effectiveness of nutritional interventions to prevent or treat maternal morbidity, mortality and preterm delivery. Cochrane systematic reviews and other up-to-date systematic reviews and individual randomized controlled trials were sought. Searches were carried out up to July 2002. Iron and folate supplements reduce anemia and should be included in antenatal care programs. Calcium supplementation to women at high risk of hypertension during pregnancy or low calcium intake reduced the incidence of both preeclampsia and hypertension. Fish oil and vitamins E and C are promising for preventing preeclampsia and preterm delivery and need further testing. Vitamin A and beta-carotene reduced maternal mortality in a large trial; ongoing trials should provide further evaluation. No specific nutrient supplementation was identified for reducing preterm delivery. Nutritional advice, magnesium, fish oil and zinc supplementation appear promising and should be tested alone or together in methodologically sound randomized controlled trials. Anema in pregnancy can be prevented and treated effectively. Considering the multifactorial etiology of the other conditions evaluated, it is unlikely that any specific nutrient on its own, blanket interventions or magic bullets will prevent or treat preeclampsia, hemorrhage, obstructed labor, infections, preterm delivery or death during pregnancy. The few promising interventions for specific outcomes should be tested or reconsidered when results of ongoing trials become available. Until then, women and their families should receive support to improve their diets as a general health rule, which is a basic human right.

Calcium to creatinine ratio in a spot sample of urine for early prediction of pre-eclampsia

OBJECTIVES

Based on the fact that urinary calcium excretion decreases in pre-eclampsia, this study was designed to determine the predictive value of calcium to creatinine ratio in a spot urine sample.

METHODS

The calcium to creatinine ratio was measured in a spot urine sample of 102 normotensive women at 20-24 weeks' gestation who attended the prenatal care clinic of the Shiraz University of Medical Sciences. The women were followed-up until delivery and grouped according to pre-eclampsia occurrence. The prevalence of pre-eclampsia was measured and compared with the calcium to creatinine ratio.

RESULTS

Ninety-four women remained normotensive during pregnancy and eight developed pre-eclampsia. Mean age, gestational age at the beginning of the study, and gestational age at delivery did not differ significantly between the two groups. Mean urinary calcium concentration (15.9+/-8.5 mg/dl in normotensive vs. 10.2+/-7.5 mg/dl in pre-eclamptic women), and mean birth weight (3192+/-336.3 g vs. 2712+/-468.9 g) were significantly lower in pre-eclamptic patients (P=0.03 and 0.005, respectively). Mean calcium to creatinine ratio was also significantly lower in the pre-eclamptic group (P<0.03).

CONCLUSIONS

Single urine calcium to creatinine ratio may be an effective method for screening women at greatest risk for pre-eclampsia.

The concentrations of osteocalcin and degradation products of type I collagen in pregnant women with pre-eclampsia

OBJECTIVES

To investigate the concentrations of osteocalcin and collagen type I C-terminal telopeptides in pregnant women with pre-eclampsia.

STUDY DESIGN

26 patients with severe pre-eclampsia and 24 healthy pregnant women were included in the study. Serum concentrations of osteocalcin and C-telopeptides--degradation products of type I collagen were determined using the ELISA method. Statistical analysis was performed using Mann-Whitney U-test.

RESULTS

In pre-eclamptic patients, the concentrations of osteocalcin and degradation products of collagen type I were significantly higher (P<0.005) when compared to healthy pregnant women.

CONCLUSION

These results could suggest that there are alterations in bone metabolism in pregnant women with pre-eclampsia.

Calcium in pregnancy and lactation

Pregnancy and lactation are periods of high calcium requirement. This review highlights recent advances in our understanding of calcium and bone metabolism during human pregnancy and lactation and discusses the findings in relation to the calcium nutrition of the mother. The evidence indicates that pregnancy and lactation are characterized by physiological adaptive processes that are independent of maternal calcium intake and that provide the calcium necessary for fetal growth and breast-milk production without requiring an increase in maternal calcium intake. There are firm data that demonstrate that a low calcium intake during lactation does not lead to impaired lactational performance or to exaggerated bone loss. However, more research is required to define whether a low calcium intake prior to or during pregnancy can have deleterious effects on reproductive and lactational performance, and on the long-term health of the mother and child.

Dietary calcium and pregnancy-induced hypertension: is there a relation?

The evidence that calcium plays a role in the etiology, prevention, and treatment of pregnancy-induced hypertension (PIH) is reviewed. The precise factors involved in the pathogenesis of PIH are unclear, but several alterations in calcium metabolism have been identified. Epidemiologic data suggest an inverse correlation between dietary calcium intake and incidence of PIH. Although evidence suggests a possible beneficial effect of supplemental calcium, contradictions persist in clinical trials of pregnant women. Presently, there is insufficient evidence to support routine calcium supplementation of all pregnant women. However, high-risk groups, such as pregnant teens, populations with inadequate calcium intake, and women at risk of developing PIH, may benefit from consuming additional dietary calcium.

Third-trimester amniotic fluid metal levels associated with preeclampsia

Studies of maternal amniotic fluid and serum at delivery have revealed the presence of toxic metals or deficiencies of essential metals associated with high-risk pregnancy. Essential and toxic metal levels were studied in 29 preeclamptic and 101 normal pregnancies. The authors grouped the samples according to the following gestation ages: 33-36 wk (48 normal and 10 preeclamptic) and 37-40 wk (53 normal and 19 preeclamptic). The metals studied were calcium, magnesium, zinc, selenium, copper, cadmium, and lead. Comparisons of the 33-36-wk gestation group showed significant differences between normal and preeclamptic amniotic fluid in levels of lead, calcium, magnesium, zinc, and selenium. There were also significant differences in levels of magnesium, copper, zinc, cadmium, and lead during the gestation period of 37-40 wk. The changes observed in calcium and lead levels were consistent with the results of animal studies in which investigators have found depressed calcium transport associated with subacute or chronic lead poisoning, resulting in a physical syndrome similar to preeclampsia.

Calcium metabolism in pre-eclampsia

OBJECTIVES

To study calcium metabolism in pre-eclampsia and normotensive gravid women.

METHOD

Ten milliliters of heparinized blood samples and 24-h urine samples were collected from 50 pre-eclamptic and 50 normotensive primigravidae. Blood samples were studied for calcium uptake, intracellular calcium level and calcium-dependent adenosine triphosphatase activity of red blood cell ghost. Urinary calcium excretion was estimated from the 24-h urine samples. These values were compared in the two groups.

RESULTS

The mean gestational age at recruitment was similar in both the groups. The mean maternal age was 24.28 +/- 2.41 years in pre-eclamptic and 23.48 +/- 4.16 years in normotensive women. In pre-eclampsia 24-h urinary calcium excretion (71.20 +/- 22.95 mg/day) and calcium-dependent ATPase activity (10.78 +/- 2.40 nmol/Pi/mg protein/min) was significantly lower compared to normotensive primigravidae (calcium excretion = 189.24 +/- 57.06 mg/day; Ca2+-dependent ATPase = 12.64 +/- 2.42 nmolPi/mg /protein per min; P < 0.001). Intracellular calcium levels and calcium uptake at 10 min by red blood cells were significantly higher in pre-eclampsia (P < 0.05). Calcium uptake by red blood cells at 20 and 30 min was similar in both groups.

CONCLUSION

Pre-eclampsia is associated with increased levels of intracellular calcium, decreased calcium-dependent ATPase activity of erythrocytes and hypocalciuria.