Comparative study of assessment of renal function in pregnant women with non-pregnant women

 

 

Abstract               Background: Pregnancy is dynamic physiological state in women’s life. Present study carried out in 50 pregnant and 50 non-pregnant women subjects with different age group and different BMI groups and comparison of renal function parameters like serum urea, creatinine, electrolytes and uric acid level between pregnant and non-pregnant women. Material and methods: Serum was collected in plain bulb and we have measured renal function parameters like serum urea, creatinine and uric acid in Erba XL-640 fully auto analyzer and electrolytes in AFT 500 electrolyte analyzer, in tertiary care hospital Surat. Statistical calculation was done by using SPSS v 16 software. Result and discussion: There is a significant reduction (p<0.001) in serum urea, significant reduction (p<0.001) in serum creatinine and significant increased (p<0.001) in serum uric acid level in pregnant women compared to non-pregnant women. Conclusions: We have observed significant reduction of serum urea in pregnant women compared to non-pregnant women. This may be due to hemodilution due to expansion of fluid volume. We also have observed similar significant reduction of serum creatinine in pregnant women compared to non-pregnant women which is due to hemodilution effect and increased GFR in pregnant women. We have observed significant increase in serum level of uric acid in pregnant women compared to non-pregnant women which is due to effect of alteration of renal function which may will be associated with pre-eclampsia.

Key Word: GFR, Urea, Creatinine, Electrolytes.

 

 

INTRODUCTION

Pregnancy is a normal physiological phenomenon with many anatomical, physiological and biochemical changes which occurs starting from the conception and extends up to the birth of newborn and subsides after delivery. These changes can be observed by measuring various biochemical parameters like glucose, lipids, electrolytes, urea, creatinine, uric acids, proteins, including different trace elements and vitamins. The result of biochemical tests during pregnancy may therefore differ from the normal reference ranges, so they may be mistakenly interpreted as abnormal. Which may sometime falsely lead to unnecessary and dangerous therapeutic action¹. Mostly the period of pregnancy is divided into two halves based on the metabolic state and development during pregnancy as first half as an anabolic phase whereby pregnant women accumulates most of the nutrients in regard to future increased demand for the supply to the fetus and health of self. In the second phase known as catalytic phase there is increased catalytic activity aimed at to fulfil the increased demands of the fetus. There is a so many anatomical and physiological changes occur due to increase in vascular and interstitial space in kidney which lead to enlargement of kidney. The most marked structural changes are the dilatation of the calyces, renal pelvis and ureters resulting in hydronephrosis. Which is most commonly founded with variable frequency and peak incidence found at late pregnancy. This changes happen from the effect of progesterone on the tone and force of contraction of the ureter to the compression effect exerted by the weight of the uterus as the pregnancy advances². There is an increased Glomerulus filtration rate due to increase in the level of aldosterone which expands the blood volume and increase renal blood flow. Oncotic pressure decreased due to volume expansion further augments filtration at the glomerulus by increasing filtration pressure. There may be increased uric acid excretion noted in first and second trimesters of pregnancy results in a decreased in serum levels. This is followed by a gradual rise in the third trimester. Which is due to the need to accommodate the increased production from the placenta and foetus. Renal function test classified as glomerular and tubular function tests assess the ability of the kidney to carry out its various functions. Biochemical parameters routinely measured include urea, electrolyte sodium (Na+), bicarbonate (HCO3-), chloride (Cl-), potassium (K+) and creatinine as well as uric acid. The increase in renal blood flow and glomerular filtration rate which lead to increase in cardiac output, increase in progesterone and aldosterone. As a result of this, increase in glomerular filtration rate, the clearance of urea, uric acid and creatinine increases and their plasma levels are decreased in pregnancy. The biochemical Changes in renal function in normal pregnancies and future outcome associated with in various region is not well documented. Thus, the purpose of this study was to measure various renal biochemical parameters like serum urea, creatinine, electrolytes (sodium, potassium and chloride) and uric acid level to observe the finding in pregnant women compared to non-pregnant women. Renal function can be evaluated by the estimation of urea, creatinine, electrolytes and uric acid levels in serum/plasma. If renal function deteriorate than it affects on body fluids include generalized edema, acidosis, and high level of protein nitrogen, increased level of urea, creatinine, and other nitrogenous product of amino acid, this condition known as uremia, which results from the failure of the kidneys to maintain adequate excretory, regulatory and endocrine functions. So, the clinical chemistry laboratory has an important role in the management of pregnancy. In addition, there seems to be dearth of information on the values of renal function tests of pregnant women in plateau state. This study was therefore initiated to determine the levels of serum uric acid, creatinine, urea and electrolytes at first trimesters of pregnancy and evaluate the risk associated with changes in renal functions of pregnant women. Uric acid is a breakdown product of purine metabolism. Its increased level in serum is indicator of gout. During pregnancy uric acid level falls to low level in early and middle pregnancy and rises back to normal in late pregnancy. Most of literature report support the association of uric acid level with pregnancy induced hypertension³. Increased uric acid concentration is one of the most pronounced clinical findings in preeclampsia. Due to reduction in glomerular filtration rate due to endothelial dysfunction, uric acid level increased in preeclampsia^4,5. Several studies have reported that increased in level of serum uric acid is positively correlated with adverse maternal and fetal outcomes^6,7. However, others cited that an increased in level of uric acid is a poor predictor of maternal and fetal outcomes^8,9.In this study we have done comparison of renal biochemical parameters like serum urea, creatinine, electrolytes and uric acid level in pregnant women compared to non-pregnant women.

 

MATERIAL AND METHODS

The present study was carried out in the tertiary care hospital, Surat. In present study there is 50 pregnant women and 50 non-pregnant women from total 100 women subjects. Women are again divided in age wise, <25 years of age group 22 are pregnant and 20 are non-pregnant, between 25 to 30 years, 23 are pregnant and 23 are non-pregnant and ≥ 30 year of age group 5 are pregnant and 7 are non-pregnant. Women again classified by BMI wise, <23 kg/m² of BMI group, 5 are pregnant and 28 are non-pregnant, between 23-24.99 kg/m² of BMI, 22 are pregnant and 8 are non-pregnant and 25-29.99 kg/m² of BMI group 23 are pregnant and 11 are non-pregnant and ≥30 kg/m² of BMI group 5 are pregnant and 3 are non-pregnant. Subject were selected from outdoor and departments. Estimation of various biochemical parameters like serum urea, creatinine, uric acid and calcium level were measured by Erba XL-640 fully auto analyzer. Electrolytes (sodium, potassium and calcium) was measured by electrolyte analyzer AFT 500.We have excluded women with chronic disorders like diabetes mellitus, thyroid disorder or any other gynecological disorder in this study. We have also excluded 2^nd and 3^rd trimester of pregnant women. We have also measured anthropological parameters like height and weight, based on this we have calculated BMI in kg/m².

Statistical analysis: Statistical data analysis was done by using SPSS software. Student’s’ test was used for present study and p value <0.05 was considered statistically significant and p value <0.001 was considered to be highly statistically significant.

 

RESULT

Table 1: Comparison of renal function (serum urea, creatinine, electrolytes, uric acid and calcium level) and systolic and diastolic blood pressure level in pregnant women with non-pregnant women.

Above mentioned table shows that, there is a significant (p<0.001) reduction in systolic and diastolic blood pressure in pregnant women compared to non-pregnant women. There is significant (p<0.001) reduction in serum urea and creatinine level in pregnant women compared to non-pregnant women. There is decreased level of electrolytes (sodium and potassium) in pregnant women compared to non-pregnant women but statistically not significant. There is significant (p<0.001) increased in serum uric acid level in pregnant women compared to non-pregnant women.

 

Table 2: Comparison of renal function (serum urea, creatinine, electrolytes, uric acid and calcium level) and systolic and diastolic blood pressure in pregnant and non-pregnant women in age group of < 25 years, 25 – 29 years and ≥30 years

There is an increasing pattern of systolic blood pressure observed in pregnant women with increased age but there is not any pattern observed in diastolic blood pressure in pregnant women. There is a significant decreased level of serum urea and creatinine in pregnant women all age group except in ≥30 year’s group compared to non-pregnant women. In electrolytes there is no any kind of pattern observed. There is a significant (p<0.01) increased level in serum uric acid in pregnant women of 25-30 years age group.

 

Table 3: Comparison of renal function (serum urea, creatinine, electrolytes, uric acid and calcium) level and systolic and diastolic blood pressure in pregnant and non-pregnant women in BMI (body mass index) of < 23 kg/m², 23-25 kg/m2, 25 – 29 kg/m² and ≥30 kg/m²

 

There is a significant decreased in diastolic blood pressure in all BMI groups except in ≥30 kg/m² group in pregnant women compared to non-pregnant women and systolic blood pressure decreased in <23 kg/m² and 25-29.9 kg/m² in pregnant women compared to non-pregnant women. There is a significant decreased in serum urea level in <23 kg/m² and ≥30 kg/m² in pregnant women compared to non-pregnant women. There is a significant reduction in serum creatinine level in all BMI group in pregnant women except in 23-25 kg/m² compared to non-pregnant women. There is not any significant finding observed in electrolytes in pregnant women compared to non-pregnant women. There is a significant increase in serum uric acid level in pregnant women in all BMI groups except 23-25 kg/ m² compared to non-pregnant women.

DISCUSSION

In present study we have performed renal function parameters like serum urea, creatinine, electrolytes (sodium, potassium and chloride) and uric acid in pregnant women compared to non-pregnant women, we have also measured systolic and diastolic blood pressure in pregnant and non-pregnant women. In present study we have found significant (p<0.001) decreased in systolic and diastolic blood pressure in all age and BMI groups of pregnant women compared to non-pregnant women which mostly due to hormonal changes and circulation expands which cause blood vessels to dilate lead to lower blood pressure. We have observed significant (p<0.001) decreased serum urea (17.8 ± 4.82 mg/dl)in pregnant women compared to non-pregnant women (21.5 ± 5.1 mg/dl). Reduction in serum urea due to hemodilution occur in pregnancy and also due to alteration liver condition. We have also observed significant decreased level of urea in all age groups in pregnant women except in higher age compared to non-pregnant women. We have also observed significant decreased level of urea in <23 kg/m² group but in other BMI group not significant reduction in pregnant women compared to non-pregnant women. Similar pattern was found in study conducted by other researchers. In case of serum level of creatinine we have observed significant (p<0.001) reduction in pregnant women (0.65 ± 0.13 mg/dl) compared to non-pregnant (0.86 ± 0.18) women. Which may be due to physiological increased in glomerular filtration rate which may lead to decreased in serum creatinine, other reason cited that hemodilution may lead to lower the creatinine level in pregnant women. We have also observed significant reduction of creatinine in all age groups except higher age group compared to non-pregnant women. We have also observed significant reduction in serum creatinine in all BMI groups except 23-25 kg/m² compared to non-pregnant women. Similar pattern was observed by other researchers. We have also measured serum electrolytes like sodium, potassium and chloride in pregnant women. We observed that, there is not significant reduction of sodium level in pregnant women to non-pregnant women this may be due to hemodilution occur due to fluid overload in pregnancy. Study conducted by other researchers find unchanged in level of serum sodium in pregnant women¹⁰. In case of serum potassium, we have observed non-significant reduction in pregnant women compared to non-pregnant women. Which may be due to hemodilution occur due to fluid overload in pregnancy. This low potassium is associated with lower risk of gestational diabetes and pre-eclampsia. ¹¹. In case of serum chloride, we have observed significant increased level in pregnant women compared to non-pregnant womenbut this result in not par with finding of¹⁰. We have also measured uric acid level in pregnant women compared to non-pregnant women. We have observed significant (p<0.001) increased level of serum uric acid in pregnant women (5.71 ± 2.31 mg/dl) compared to non-pregnant (3.92 ± 2.18 mg/dl) women. Which is may be associated with oxidative stress and renal function impairment as result of placental ischemia and reduced maternal GFR¹². Mazzali et al¹³shows an increased in serum uric acid followed by an increase in blood pressure via a crystal-independent mechanism in rat models. Lower level of serum uric acid was associated with a decrease in blood pressure through the regulation of renin angiotensin and nitric oxide system¹⁴.Increasing level of serum uric acid in pregnant women may lead to develop hypertension due to uric acid mediated renal vasoconstriction resulting from reduction in endothelial level of nitric oxide. As per above all finding of renal biochemical parameters in pregnant women, we can conclude that, biochemical parameters like serum urea, creatinine, electrolytes and mainly uric acid need to estimate in pregnant women to prevent any unwanted complication arrived due to increase in any of above parameters. This study will further help to other researchers to focus more on upcoming event happen in pregnancy and also after post-partum. Which help in proper management of pregnancy outcome and better development of fetus and maternal health.

 

 

CONCLUSION

We have observed significant reduction of serum urea in pregnant women compared to non-pregnant women. We also have observed similar significant reduction of serum creatinine in pregnant women compared to non-pregnant women. We have observed significant increase in serum level of uric acid in pregnant women compared to non-pregnant women. We have also measured serum electrolytes like sodium, potassium and chloride in pregnant women which shows that reduction of electrolyte but not significant in pregnant women compared to non-pregnant women.

 

LIMITATION

This study is limited to only 50 pregnant women and 50 non-pregnant women, and study not conducted post-partum effect, and also not conducted any other investigation other than serum urea, creatinine, electrolytes and uric acid.

 

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