Why is the treatment of hypertension in pregnancy still so difficult?

Different Doses of Calcium Supplementation to Prevent Gestational Hypertension and Pre-Eclampsia: A Systematic Review and Network Meta-Analysis

Objective

Calcium supplementation can prevent gestational hypertension and pre-eclampsia. However, besides the non-consensus of existing studies, there is a lack of evidence regarding the optimal dosing of calcium.

Method

Eight electronic databases, namely, the Cochrane Library, PUBMED, Web of Science, EMBASE, WANGFANG, VIP, CBM, and CNKI, were searched. The studies were retrieved from inception to July 13, 2021. Two researchers independently screened the literature, extracted data, and evaluated the methodological quality based on the inclusion criteria. In particular, the calcium supplementation doses were divided into three groups, namely, the high-dose (≥1.5 g), medium-dose (1.0–1.49 g), and the low-dose group (<1.0 g). The participants were also divided into high-risk and low-risk groups, according to the risk of developing gestational hypertension and pre-eclampsia.

Results and Discussion

A total of 48 studies were incorporated into the final analyses. All doses of calcium supplementation reduced the incidence of gestational hypertension in the low-risk population (low dose - three studies; medium dose- 11 studies; high dose- 28 studies), whereas the medium-dose (three studies) reduced the incidence of gestational hypertension in high-risk groups. Moreover, a medium dose of calcium supplementation had the maximum effect in reducing gestational hypertension in low-risk and high-risk populations. The medium (three studies) and high doses (13 studies) of calcium supplementation reduced the incidence of pre-eclampsia in the low-risk groups. However, a medium-dose calcium supplementation maximally prevented pre-eclampsia in the low-risk population. The authenticity and reliability of the results were reduced due to the limitations of contemporary studies in terms of experimental design, result measurement, statistics, and evidence quality. Therefore, high-quality studies with larger sample size are required to evaluate further the effect of calcium supplementation in preventing gestational hypertension and pre-eclampsia.

Mechanisms and Clinical Significance of Endothelial Dysfunction in High-Risk Pregnancies

The maternal cardiovascular system undergoes critical anatomic and functional adaptations to achieve a successful pregnancy outcome which, if disrupted, can result in complications that significantly affect maternal and fetal health. Complications that involve the maternal cardiovascular system are among the most common disorders of pregnancy, including gestational hypertension, preeclampsia, gestational diabetes, and impaired fetal growth. As a central feature, maternal endothelial dysfunction is hypothesized to play a predominant role in mediating the pathogenesis of these high-risk pregnancies, and as such, might proceed and precipitate the clinical presentation of these pregnancy disorders. Improving or normalizing maternal endothelial function in high-risk pregnancies might be an effective therapeutic strategy to ameliorate maternal and fetal clinical outcomes.

Folic acid alone or multivitamin containing folic acid intake during pregnancy and the risk of gestational hypertension and preeclampsia through meta-analyses

Objective

The objective of this study was to assess the effect of folic acid and multivitamin use during pregnancy on the risk of developing of hypertensive disorder of pregnancy.

Methods

Two reviewers independently determined all prospective cohort study, retrospective cohort study, large population based cohort study, retrospective secondary analysis, and double blinded, placebo-controlled, randomized clinical trial published using PubMed Medline database, KERIS (Korea Education and Research Information Service), Scopus, and the Cochrane Central Register of controlled trials comparing before conception throughout pregnancy intake oral multivitamin containing folic acid or folic acid alone. Meta-analyses were estimated with odds ratios and 95% confidence intervals (CIs) using random effect analysis according to heterogeneity of studies.

Results

Data from six effect sizes from six studies involving 201,661 patients were enrolled. These meta-analyses showed multivitamin containing folic acid or folic acid alone was not significantly effective in reducing gestational hypertension or preeclampsia incidence (odds ratio, 0.91; 95% CI, 0.81 to 1.03) than the placebo. And the difference of effective sizes of preeclampsia and gestational hypertension according to two dependent variables, multivitamin and folic acid were not significant, respectively (point estimate, 0.66; 95% CI, 0.46 to 0.96).

Conclusion

These meta-analyses demonstrate multivitamin containing folic acid or folic acid alone was not significantly effective in reducing gestational hypertension or preeclampsia incidence.

Hypertension in pregnancy

Hypertensive disorders of pregnancy represent the second commonest cause of direct maternal death and complicate an estimated 5-10 % of pregnancies. Classification systems aim to separate hypertension similar to that seen outside pregnancy (chronic and gestational hypertension) from the potentially fatal pregnancy-specific conditions. Preeclampsia, HELLP syndrome, and eclampsia represent increasing severities of this disease spectrum. The American College of Obstetricians and Gynecologists' 2013 guidelines no longer require proteinuria as a diagnostic criterion, because of its variable appearance in the disease spectrum. The cause involves inadequate cytotrophoblastic invasion of the myometrium, resulting in placental hypoperfusion and diffuse maternal endothelial dysfunction. Changes in angiogenic and antiangiogentic peptide profiles precede the onset of clinical preeclampsia. Women with preeclampsia should be closely monitored and receive magnesium sulfate intravenously if severe features, HELLP syndrome, or eclampsia occur. Definitive therapy is delivery of the fetus. Hypertension in pregnancy increases future maternal risk of hypertension and cardiovascular disorders.

Hypertension in pregnancy

Hypertension in pregnancy is diagnosed on systolic blood pressure greater than or equal to 140 mm Hg and/or diastolic greater than or equal to 90 mm Hg. The classification systems separate chronic and gestational hypertension from preeclampsia. Significant uncertainty regarding optimal management is reflected in the differing major international society recommendations. Blood pressure treatment is designed to minimize maternal end-organ damage. Methyldopa, labetalol, hydralazine, and nifedipine are oral options; angiotensin-converting enzyme inhibitors and angiotensin receptor antagonists are contraindicated. Women with preeclampsia should be closely monitored and receive intravenous magnesium sulfate.