Hypertensive disorders during pregnancy, including gestational hypertension and pre-eclampsia, are among the leading causes of maternal and fetal complications worldwide. These conditions affect approximately 5–10% of pregnancies and are associated with increased risks of preterm birth, fetal growth restriction, and maternal cardiovascular diseases (1,2). Pre-eclampsia is characterized by hypertension and proteinuria after 20 weeks of gestation, whereas gestational hypertension presents as elevated blood pressure without proteinuria (3). The exact pathophysiology of these disorders remains unclear, but endothelial dysfunction, oxidative stress, and altered vascular reactivity are believed to play key roles (4).

Calcium and magnesium are essential minerals that contribute to vascular homeostasis and blood pressure regulation. Calcium influences vascular smooth muscle contraction and endothelial function, while magnesium acts as a natural calcium antagonist, promoting vasodilation and reducing inflammation (5,6). Studies have reported an association between reduced serum calcium and magnesium levels with an increased risk of hypertension and pre-eclampsia in pregnancy (7,8). Hypocalcemia has been linked to increased parathyroid hormone secretion, leading to vasoconstriction and endothelial dysfunction, while magnesium deficiency may contribute to heightened vascular resistance and oxidative stress (9,10).

Despite existing research, the relationship between serum calcium, magnesium, and hypertensive disorders in pregnancy remains inconclusive due to variations in study populations, methodologies, and sample sizes. This study aims to evaluate the association of serum calcium and magnesium levels in women with gestational hypertension and pre-eclampsia, providing further insights into their potential role in the pathophysiology of these conditions. Understanding these associations may help in the development of preventive and therapeutic strategies to reduce maternal and fetal morbidity associated with hypertensive disorders in pregnancy.

Study Design and Setting

A hospital-based cross-sectional study was conducted at a tertiary care center over a period of six months. The study aimed to assess the relationship between serum calcium and magnesium levels in pregnant women with gestational hypertension and pre-eclampsia.

Study Population

The study included a total of 100 pregnant women, categorized into three groups: normotensive pregnant women (n=40), women diagnosed with gestational hypertension (n=30), and women with pre-eclampsia (n=30). The inclusion criteria consisted of singleton pregnancies beyond 20 weeks of gestation. Women with pre-existing hypertension, renal disorders, diabetes mellitus, or those on calcium or magnesium supplements were excluded.

Data Collection and Laboratory Analysis

Venous blood samples (5 mL) were collected from all participants following an overnight fast. The samples were centrifuged at 3,000 rpm for 10 minutes, and the serum was separated for biochemical analysis. Serum calcium and magnesium levels were measured using an automated biochemical analyzer based on the colorimetric method.

Clinical and Blood Pressure Assessment

Blood pressure was measured using a standard sphygmomanometer with the participant in a sitting position. Hypertension was defined as a systolic blood pressure ≥140 mmHg and/or a diastolic blood pressure ≥90 mmHg on two separate occasions at least four hours apart. Pre-eclampsia was diagnosed based on hypertension accompanied by proteinuria (≥300 mg/24 hours) or other systemic complications.

Statistical Analysis

Data were analyzed using SPSS software version 25.0. Mean and standard deviation (SD) were calculated for continuous variables, while categorical variables were expressed as frequencies and percentages. One-way ANOVA was used to compare serum calcium and magnesium levels among the three groups. Pearson’s correlation was applied to evaluate the association between serum electrolytes and hypertensive status. A p-value of <0.05 was considered statistically significant.

A total of 100 pregnant women participated in the study, with 40 in the normotensive group, 30 diagnosed with gestational hypertension, and 30 with pre-eclampsia.

Serum Calcium and Magnesium Levels

The mean serum calcium and magnesium levels were significantly lower in women with pre-eclampsia compared to those with gestational hypertension and normotensive women. The normotensive group had the highest mean serum calcium level (9.1 ± 0.5 mg/dL), followed by the gestational hypertension group (8.6 ± 0.3 mg/dL) and the pre-eclampsia group (8.1 ± 0.4 mg/dL). A similar trend was observed in serum magnesium levels, with mean values of 2.0 ± 0.4 mg/dL in normotensive women, 1.7 ± 0.3 mg/dL in the gestational hypertension group, and 1.5 ± 0.2 mg/dL in the pre-eclampsia group. These differences were statistically significant (p<0.05) (Table 1).

Correlation Between Serum Calcium, Magnesium, and Blood Pressure

A negative correlation was found between serum calcium and blood pressure parameters. Serum calcium showed a moderate negative correlation with systolic blood pressure (r = -0.52, p<0.01) and diastolic blood pressure (r = -0.47, p<0.05). Similarly, serum magnesium levels were inversely correlated with systolic blood pressure (r = -0.55, p<0.01) and diastolic blood pressure (r = -0.49, p<0.05), suggesting that lower levels of these electrolytes are associated with increased blood pressure in hypertensive pregnancies (Table 2). ​​

Table 1: Serum Calcium and Magnesium Levels

Table 2: Correlation Between Serum Calcium, Magnesium, and Blood Pressure

Hypertensive disorders in pregnancy, including gestational hypertension and pre-eclampsia, are significant causes of maternal and fetal complications worldwide. Understanding the role of essential minerals such as calcium and magnesium in blood pressure regulation may contribute to better management and prevention strategies for these conditions (1,2). This study found significantly lower serum calcium and magnesium levels in pregnant women with gestational hypertension and pre-eclampsia compared to normotensive women, supporting previous findings that deficiencies in these electrolytes may contribute to the pathophysiology of hypertensive disorders in pregnancy (3,4).

Calcium plays a crucial role in vascular function by regulating vasoconstriction and endothelial cell activity. Hypocalcemia has been associated with increased levels of parathyroid hormone, leading to vasoconstriction and elevated blood pressure (5,6). In the present study, serum calcium levels were significantly reduced in women with gestational hypertension and pre-eclampsia, in line with research indicating that low calcium levels may contribute to increased vascular resistance and endothelial dysfunction (7,8). The inverse correlation between serum calcium and blood pressure parameters further highlights its potential role in maintaining vascular homeostasis (9).

Magnesium, a natural calcium antagonist, plays an essential role in vascular relaxation by inhibiting calcium influx into vascular smooth muscle cells. Magnesium deficiency has been linked to endothelial dysfunction, oxidative stress, and increased vascular resistance, all of which contribute to hypertensive disorders (10,11). In this study, serum magnesium levels were significantly lower in pre-eclamptic women compared to normotensive pregnant women, which is consistent with prior studies reporting that hypomagnesemia is associated with increased blood pressure and endothelial damage (12,13). The negative correlation between serum magnesium and both systolic and diastolic blood pressure in this study suggests that magnesium insufficiency may exacerbate hypertensive conditions (14).

The observed association between decreased serum calcium and magnesium levels and hypertensive disorders in pregnancy suggests the potential benefits of dietary supplementation and monitoring. Previous studies have shown that calcium supplementation during pregnancy can reduce the risk of developing pre-eclampsia, particularly in populations with low dietary calcium intake (15). Similarly, magnesium supplementation has been recommended to improve endothelial function and reduce blood pressure in hypertensive pregnancies (16,17).

Despite these findings, this study has some limitations, including a relatively small sample size and its cross-sectional design, which limits the ability to establish a causal relationship between serum electrolyte levels and hypertensive disorders. Future research with larger sample sizes and longitudinal follow-up is required to further explore these associations and determine the potential therapeutic effects of calcium and magnesium supplementation in preventing hypertensive disorders during pregnancy

1. Ephraim RKD, Osakunor DNM, Denkyira SW, Eshun H, Amoah S, Anto EO. Serum calcium and magnesium levels in women presenting with pre-eclampsia and pregnancy-induced hypertension: a case-control study in the Cape Coast metropolis, Ghana. BMC Pregnancy Childbirth. 2014;14:390.
2. Bera S, Adak RS, Gupta S, Roy TG, Taraphdar P, Bal R, et al. Study of serum electrolytes in pregnancy induced hypertension. J Indian Med Assoc. 2011 Aug;109(8):546-8.
3. Roberts JM, Cooper DW. Pathogenesis and genetics of pre-eclampsia. Lancet. 2001;357(9249):53-6.
4. Sibai BM, Dekker G, Kupferminc M. Pre-eclampsia. Lancet. 2005;365(9461):785-99.
5. Ray JG, Vasishta S, Kahn SR, Rioux L, Payne M, Ross S, et al. Association of complications of pregnancy with the development of elevated blood pressure: a systematic review. Hypertension. 2005;46(4):1027-34.
6. Trumbo PR, Ellwood KC. Supplemental calcium and risk reduction of hypertension, pregnancy-induced hypertension, and preeclampsia: an evidence-based review by the US Food and Drug Administration. Nutr Rev. 2007;65(2):78-87.
7. Hofmeyr GJ, Lawrie TA, Atallah ÁN, Duley L. Calcium supplementation during pregnancy for preventing hypertensive disorders and related problems. Cochrane Database Syst Rev. 2018;10:CD001059.
8. Makrides M, Crosby DD, Bain E, Crowther CA. Magnesium supplementation in pregnancy. Cochrane Database Syst Rev. 2014;4:CD000937.
9. Oladipo OO, Afolabi BB, Okorodudu AO. Plasma total and ultrafiltrable calcium in normal pregnancy, hypertension in pregnancy and pre-eclampsia. Niger Postgrad Med J. 2007;14(3):213-6.
10. He L, Lang L, Li Y, Liu Q, Yao Y. Comparison of serum zinc, calcium, and magnesium concentrations in women with pregnancy-induced hypertension and healthy pregnant women: A meta-analysis. Hypertens Pregnancy. 2016;35(2):202-9.
11. Wang Y, Tang HR, Wang Y, Zheng MM, Ye XD, Dai YM, et al. [Association between gestational blood pressure and pregnancy induced hypertension or pre-eclampsia]. Zhonghua Fu Chan Ke Za Zhi. 2021;56(11):767-73.
12. Kasim HH, Masri MA, Noh NA, Mokhtar A, Mokhtar RH. Clinical implications of blood pressure variability (BPV) in pregnancies: a review. Horm Mol Biol Clin Investig. 2019;39(3):/j/hmbci.2019.39.issue-3/hmbci-2018-0060/hmbci-2018-0060.xml.
13. Schenkelaars N, Rousian M, Hoek J, Schoenmakers S, Willemsen S, Steegers-Theunissen R. Preconceptional maternal weight loss and hypertensive disorders in pregnancy: a systematic review and meta-analysis. Eur J Clin Nutr. 2021;75(12):1684-97.
14. Ajong AB, Yakum MN, Aljerf L, Ali IM, Mangala FN, Onydinma UP, et al. Association of hypertension in pregnancy with serum electrolyte disorders in late pregnancy among Cameroonian women. Sci Rep. 2023;13(1):20940.
15. Uddin SMN, Haque M, Barek MA, Chowdhury MNU, Das A, Uddin MG, et al. Analysis of serum calcium, sodium, potassium, zinc, and iron in patients with pre-eclampsia in Bangladesh: A case-control study. Health Sci Rep. 2023;6(2):e1097.
16. Oken E, Ning Y, Rifas-Shiman SL, Rich-Edwards JW, Olsen SF, Gillman MW. Diet during pregnancy and risk of preeclampsia or gestational hypertension. Ann Epidemiol. 2007;17(9):663-8.
17. Duley L. The global impact of pre-eclampsia and eclampsia. Semin Perinatol. 2009;33(3):130-7.