Calcium-to-creatinine ratio in spot urine samples in early pregnancy and its relation to the development of preeclampsia

Urinary concentrations of mineral elements and their predictors in pregnant women in Jinan, China

BACKGROUND

The essential mineral elements play important roles in proper growth, development and maintenance of physiological homeostasis of an organism. Women are at greater risk of mineral deficiency during pregnancy. However, the predictors of mineral element levels in pregnant women remain unclear. This study was conducted to determine the urinary levels of calcium (Ca), iron (Fe), copper (Cu), manganese (Mn) and selenium (Se) in women during early pregnancy and to explore the predictors of urinary exposure to each mineral element and high co-exposure to mineral element mixture.

METHODS

298 pregnant women in first trimester were recruited when they attended antenatal care in a hospital in Jinan, Shandong Province, China. We collected their spot urine samples and questionnaire data on their sociodemographic characteristics, lifestyle habits, food and dietary supplement intake, and residential environment. The concentrations of Ca, Fe, Cu, Mn and Se in all urine samples were measured. LASSO regression, multiple linear regression and binary logistic regression were used to analyze the predictors affecting mineral element levels.

RESULTS

The geometric means of creatinine-corrected Ca, Fe, Cu, Mn and Se concentrations were 99.37 mg/g, 1.75 µg/g, 8.97 µg/g, 0.16 µg/g and 16.83 µg/g creatinine, respectively. Factors that influenced the concentrations of individual mineral element were as follows: (1) Se and Ca concentrations increased with maternal age; (2) women taking tap water as family drinking water had higher Ca levels and those taking polyunsaturated fatty acids intermittently had higher Cu levels; (3) Fe was adversely related to consumption frequency of barbecued foods; (4) Pregnant women with more frequent consumption of shellfish/shrimp/crab and living near green spaces or parks had higher Mn exposure, and those with higher frequency of meat consumption had lower Mn exposure. In addition, maternal age and the frequency of egg consumption were associated with odds of exposure to a mixture of high Ca, Fe, Cu and Se.

CONCLUSIONS

The pregnant women in this study had comparable concentrations of urinary Cu and Se but lower concentrations of Ca, Fe and Mn compared with those in other areas. Predictors of urinary mineral elements included maternal age (Se and Ca), type of domestic drinking water (Ca), consumption frequency of barbecued food (Fe), polyunsaturated fatty acid use (Cu), the presence of urban green spaces or parks near the home and frequency of meat and shellfish/shrimp/crab intake (Mn). Moreover, maternal age and egg consumption frequency were significant predictors of high-level co-exposure to urinary Ca, Fe, Cu and Se.

Evaluation of the value of calcium to creatinine ratio for predicting of pre-eclampsia

INTRODUCTION

Pre-eclampsia is one of the most serious complications in pregnancy and is one of the major causes of maternal death. Therefore, its prediction has special importance and many studies have been performed on different materials, which may be useful for its prediction.

OBJECTIVE

The purpose of the present study is to evaluate the calcium to creatinine ratio for the prediction of pre-eclampsia.

METHOD

A prospective cohort study was performed on 150 pregnant women, who were aged from 15 to 35 years. A single urine sample was obtained at 20-24 weeks of gestation for measurement of urine calcium to creatinine ratio. The women were then monitored for delivery and this ratio was compared between the women with and without pre-eclampsia.

RESULTS

Mean urine calcium of pre-eclamptic women was significantly lower than normotensive women (179 ± 35 mg/dl vs 272 ± 59 mg/dl, P < 0.001). Mean calcium to creatinine ratio was significantly lower in pre-eclamptic women (0.07 ± 0.007 vs 0.16 ± 0.006, P < 0.001). The optimal cut off point for calcium to creatinine ratio was calculated to be 0.071 with a sensitivity of 77% and specificity of 78%.

CONCLUSION

Urine calcium and calcium to creatinine ratio are lower in pre-eclamptic women and may be used as a screening test for the prediction of pre-eclampsia.

Increases in urinary creatinine and blood pressure during early pregnancy in pre-eclampsia

BACKGROUND

It is important to predict the development of pre-eclampsia (PE) during early pregnancy to prevent its occurrence later on. In this study, we studied urinary biochemical parameters and blood pressure (BP) during and after pregnancy to find useful parameters for predicting PE.

METHODS

A case-control study was performed in 25 PE patients and 172 normotensive pregnant women. Twelve biochemical parameters were measured in spot urine, and the systolic and diastolic BPs were measured using an automated device during pregnancy and six to eight weeks after birth.

RESULTS

A multiple logistic regression analysis showed that the combinations of urinary creatinine (Cr) and systolic BP (SBP) in the first trimester of pregnancy (8.9 +/- 2.6 weeks), and of urinary inorganic phosphorus (IP)/Cr and SBP in the second trimester of pregnancy (19.0 +/- 1.6 weeks) were useful for predicting PE. The area under the curve in the receiver operator characteristic curve of the combination of urinary Cr and SBP in the first trimester was 0.85 (95% confidence interval [CI] 0.74-0.96), and that of the combination of urinary IP/Cr and SBP in the second trimester was 0.91 (95% CI: 0.86-0.97). When used 249 mg/dL in urinary Cr and 128 mmHg in SBP as their cut-off points, the combination in the first trimester increased the accuracy (sensitivity 75% and specificity 95%) in predicting PE, as compared with that of urinary Cr (29%, 99%) or SBP (50%, 98%).

CONCLUSIONS

Combination of urinary Cr and SBP in early pregnancy and that of urinary IP/Cr and SBP in mid-pregnancy are useful for the prediction of PE.

Pathophysiology and medical management of systemic hypertension in preeclampsia

Hypertension that complicates preeclampsia in pregnancy is a disorder that requires special consideration in both prevention and pharmacologic treatment. In recent years, few advances have been made regarding the pathophysiology and prevention of preeclampsia; however, there have been some promising results from studies on possible modes of screening women for preeclampsia before clinical signs and symptoms are apparent. The recommendations for first-line drug therapy for the hypertensive complications of preeclampsia have changed little, primarily because first-line medications have had the advantage of extensive research experience. Recent clinical trials have demonstrated the efficacy and safety of various second-line drugs for the hypertensive complications of preeclampsia; whether these therapies can eventually replace the standard recommended first-line medications will require more extensive long-term investigation.

Pathophysiology and Medical Management of Systemic Hypertension in Pregnancy

Hypertension in pregnancy includes a group of distinct disorders that require special consideration in both prevention and pharmacologic treatment. In recent years, there have been few advances regarding the pathophysiology and prevention of preeclampsia or in the recommendations for first-line drug therapy for its hypertensive complications. Similarly, the recommendations for pharmacologic treatment of women with chronic hypertension antedating pregnancy have changed little primarily because first-line medications have the advantage of having had more extensive research experience. Recent clinical trials have demonstrated the efficacy and safety of various second-line drugs for the hypertensive disorders of pregnancy; whether these therapies can eventually replace the standard recommended medications will require more extensive long-term investigation.

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.

World Health Organization Systematic Review of Screening Tests for Preeclampsia

OBJECTIVE

We sought to assess the usefulness of clinical, biophysical, and biochemical tests in the prediction of preeclampsia.

DATA SOURCES

The sources of data we used to conduct this review included the computerized databases MEDLINE (1966 to February 2003), EMBASE, Popline, CINAHL, and LILACS plus reference lists, conference proceedings, textbooks, and contact with experts.

METHODS OF STUDY SELECTION

All cohort or cross-sectional studies reporting data on the relationship between a predictive test that was performed during pregnancy and the development of preeclampsia were eligible for inclusion, whereas case-control studies were excluded. Eighty-seven (211,369 women) of 7,191 potentially relevant articles met inclusion criteria. We evaluated the methodologic quality for each included study.

TABULATION, INTEGRATION, AND RESULTS

Using a standardized protocol, one reviewer selected and extracted data on study characteristics, quality, and accuracy. Data abstracted from each study were arranged in 2 x 2 tables to construct receiver operating characteristics plots (sensitivity against 1 - specificity) and pooled to produce summary likelihood ratios for positive and negative tests results. Moderate predictive accuracy of anticardiolipin antibodies, the presence of bilateral diastolic notches during Doppler ultrasonography, and urinary kallikrein were found in women at low risk of developing preeclampsia. Nevertheless, because the pretest probability of preeclampsia with a positive result was but minimally increased, the clinical use of these tests is limited. Other ultrasonography characteristics and the measurement of fetal and placental peptides showed low predictive accuracy. In populations that were deemed at high risk for preeclampsia, the use of Doppler ultrasonography had low predictive accuracy. No definitive conclusions were possible in the case of many other tests, because the number of studies that met the minimal inclusion criteria was limited.

CONCLUSION

As of 2004, there is no clinically useful screening test to predict the development of preeclampsia. Further prospective, longitudinal studies are needed.

Animal models of preeclampsia

There have been many attempts to produce animal models that mimic the hypertensive disorders of pregnancy, especially preeclampsia, but most are incomplete when compared to the full spectrum of the human disease. This review assesses a number of these models, organized according to the investigators attempt to focus on a specific pathogenic mechanism believed to play a role in the human disease. These mechanisms include uterine ischemia, impairments in the nitric oxide system, insulin resistance, overactivity of the autonomic nervous and/or renin-angiotensin systems, activation of a systemic inflammatory response, and most recently, activation of circulating proteins that interfere with angiogenesis. In addition a model of renal disease that mimics superimposed preeclampsia is discussed. Defining these animal models should help in our quest to understand the cause, as well as to test preventative and therapeutic strategies in the management of these hypertensive disorders of pregnancy.

Prenatal screening, epidemiology, diagnosis, and management of preeclampsia

The cause of preeclampsia remains unknown. The disease manifests itself across a broad clinical spectrum from mild to severe, conferring vastly different morbidities and suggesting possibly different disease processes. Oxidative stress, endothelial dysfunction, maternal-fetal immune incompatibility, and abnormal placental implantation are among the suggested causes. The need for a marker or set of markers that allow for definitive diagnosis and assessment of future risk of preeclampsia is tremendous. Ultrasound techniques and several markers have been identified that are increased among patients with preeclampsia, but no test is highly sensitive. In the future, a combination of markers likely will be used to assess risk and, establish the diagnosis, and test treatment strategies. Such an approach would allow for more refined treatment studies of patients who are at highest risk for preeclampsia.

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.

Serum and placental lipid peroxides in chronic hypertension during pregnancy with and without superimposed preeclampsia

OBJECTIVE

To evaluate the circulating levels of lipid peroxides and vitamin E, and the placental levels of lipid peroxides in chronic hypertensive pregnant women, with and without superimposed preeclampsia, as compared to controls and women with primary preeclampsia.

METHODS

Lipid peroxides were measured in serum and placenta by the thiobarbituric acid method and high-pressure liquid chromatography (HPLC), and vitamin E by HPLC. Patients were 36 healthy pregnant women, 34 previously nonhypertensive women diagnosed with preeclampsia, 20 women with uncomplicated chronic hypertension, and 11 women with chronic hypertension complicated by superimposed preeclampsia.

RESULTS

Lipid peroxides in serum and placental tissue were significantly increased, and vitamin E levels in serum were significantly decreased in women with primary preeclampsia and superimposed preeclampsia, as compared to controls. The group of uncomplicated chronic hypertension presented with similar values of lipid peroxides and vitamin E to controls.

CONCLUSIONS

Our results support the clinical assumption that chronic hypertension aggravated by the development of proteinuria represents a superimposed condition associated with placental disease. The data further support the concept that increased lipid peroxides are not merely associated with the presence of hypertension in pregnancy, but they are implicated in the pathophysiology of preeclampsia.

Prediction of preeclampsia

The onset of preeclampsia at or near to term is associated with low maternal and neonatal morbidity and mortality. In contrast, those patients (1%) who suffer early onset preeclampsia engender significant maternal and perinatal morbidity and mortality. Therefore, because of the lack of proven prophylaxis for preeclampsia, prediction of risk or identification of subclinical disease is desirable to identify patients for more intensive observation. There are certain at-risk groups of patients such as those with chronic hypertension, pregestational diabetes, multifetal gestation, and previous preeclampsia. These patients account for the majority of cases of preeclampsia in multiparas, yet only account for 14% of preeclampsia in nulliparous women. Thus, the majority of cases of preeclampsia arises from nulliparous women without medical complications at low risk. Differences in the time of onset, severity, and organ system involvement suggest there may be different underlying etiologies that ultimately lead to preeclampsia manifested as the triad of maternal hypertension, proteinuria, and edema. Distinct markers therefore may identify subgroups of at-risk patients with separate underlying causes. These markers ultimately could be used for diagnosis of disease before the clinical appearance of maternal disease (hypertension, proteinuria, and edema). Based on data from patients with established disease, with the involvement of various organ systems, potential candidate markers would include renal function (kallikrein-creatinine); coagulation and fibrinolytic systems and platelet activation (platelet volume); markers of vascular function (fibronectin, prostacyclin, thromboxane) and oxidant stress (lipid peroxides, 8-isoprostane, antioxidants, anticardiolipin antibodies, hemoglobin, iron, transferrin, homocysteine, hypertriglyceridemia, albumin isoforms); placental peptide hormones (CRH, CRHbp, activin, inhibin, hCG); vascular resistance (uteroplacental flow velocity waveforms); genetic markers; insulin resistance; and glucose intolerance. Although cross-sectional studies have identified these potential markers, they need to be evaluated in prospective longitudinal studies with rigorous definition of outcome to determine if they are useful in predicting preeclampsia and whether they can identify different subgroups of patients.

Animal models of preeclampsia

Some of the maternal symptoms of preeclampsia can be produced by uterine ischemia, although no quadriped spontaneously exhibits this disease. It may be that the combination of upright posture and uteroplacental ischemia are necessary for manifestation of the full syndrome. Chronic nitric oxide synthase inhibition in rats produces a pattern of change that resembles the symptoms of preeclampsia, and the preeclamptic-like response of rats with adriamycin nephropathy and hyperinsulinemia is associated with endothelial dysfunction. These models are definitely of use in preeclampsia research, but because this disease only occurs spontaneously in primates, the definitive studies on preeclampsia will, of necessity, be clinical.