Hypertensive disorders during pregnancy have been increasing over the past 10 years. In 2019, 5.4% of women who gave birth were diagnosed with chronic hypertension and 3.1% with pregnancy-induced hypertension (PIH). [1] 

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The maternal mortality due to PIH was 0.15% (5/3,263) based on nationwide multi-center data of 49 hospitals. [2]

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The PIH incidence increased with age, especially among women over 40 years of age. Among pregnant women over 40 years of age (n=22,300), the PIH incidence was 1.5% in 2011. [3] 

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PIH is one of several hypertensive disorders of pregnancy (HDPs), which are classified into four categories: gestational hypertension, preeclampsia, chronic hypertension, and chronic hypertension with superimposed preeclampsia. In terms of the onset of hypertension, HDPs are classified as gestational or chronic hypertension. In terms of the presence of proteinuria and abnormal systemic findings, HDPs are classified as preeclampsia and chronic hypertension with superimposed preeclampsia. [4] 

PIH can manifest clinically in several ways. Although some of the women may be asymptomatic, some may be symptomatic, and this includes hypertension, which is described as systolic blood pressure of 140 mmHg or above or diastolic of 90 mmHg or above as confirmed by two consecutive readings taken at least four hours apart. Proteinuria occurs together with the symptoms in some patients and may include headache, vision problems, and epigastric discomfort. [5] 

PIH during the current pregnancy period was found more frequently in women with gestational diabetes mellitus (GDM) compared to those without GDM (unadjusted OR = 1.64 [95% CI, 1.36, 1.99], p < 0.0001, adjusted by age OR = 1.61 [1.33, 1.95], p < 0.0001]). [6] 

Pregnancy-induced hypertension was defined as cases that did not meet the criteria for chronic hypertension but had insurance claims with a diagnosis of gestational hypertension (ICD-10: O13) or preeclampsia/eclampsia (ICD-10: O14, O15) within 40 weeks before or 12 weeks after delivery, based on the International Classification of Diseases, 10th Revision (ICD-10). [1] 

PIH is treated pharmacologically with the goals of regulating blood pressure, averting problems, and guaranteeing the safety of the fetus and mother. The degree of hypertension, the drug's effectiveness, and its safety profile during pregnancy all play a role in the selection of an antihypertensive treatment. [5]  We included 2,030,821 pregnancies, of whom 0.9%, 3.1%, and 1.8% were dispensed antihypertensives in the pre-pregnancy, pregnancy, and postpartum periods, respectively. The most frequent medications used were dihydropyridines (40.7%), beta-blockers (38.4%) and Angiotensin II Receptor Blockers (16.8%) in the first trimester, and dihydropyridines (89.7%) and vasodilators (11.5%) in the third trimester. Among women exposed to antihypertensives during pregnancy, this was the first use in 86.3% of women. [7] 

The gestational age of the PIH group was higher than that of the non-PIH group (27.3 ± 1.8 versus 28.0 ± 1.4 weeks, p <0.001). Birth weight was lower in the PIH group than that in the non-PIH group (876.4 ± 261.5 versus 1027.4 ± 250.2 g, p <0.001). Infants who were small-for-gestation age were more common in the PIH group than the non-PIH group (1.4% vs. 9.9%, p <0.001). [8] 

Genetic association data for the HDPs were obtained from 393 238 female individuals for gestational hypertension and 606 903 female individuals for preeclampsia. Seventy-five of 90 proteins (83.3%) had at least 1 valid cis-protein quantitative trait loci. Of those, 10 proteins (13.3%) were significantly associated with HDPs. Four were robust to sensitivity analyses for gestational hypertension (cluster of differentiation 40, eosinophil cationic protein, galectin 3, N-terminal pro-brain natriuretic peptide), and 2 were robust for preeclampsia (cystatin B, heat shock protein 27 [HSP27]). [9] 

[1] Korea hypertension fact sheet 2021: analysis of nationwide population-based data with special focus on hypertension in women. Clin Hypertens. 2022 Jan 3;28(1):1. [2] A clinical study of pregnancy - induced hypertension (PIH) in Korea in the last 7 years (1992-1998). Obstetrics & Gynecology Science (2000) 43: 2283-2292 [3] Korea Institute for Health and Social Affairs. Advanced Maternal Age Women and Adverse Birth Outcomes in Korea (2013). [4] Blood pressure control in hypertensive disorders of pregnancy. Cardiovasc Prev Pharmacother. 2022;4(3):99-105. [5] Pregnancy-Induced Hypertension Pathophysiology and Contemporary Management Strategies: A Narrative Review. Cureus. 2024 Jul 6;16(7):e63961. [6] Gestational diabetes in Korea: Temporal trends in prevalence, treatment, and short-term consequences from a national health insurance claims database between 2012 and 2016. Diabetes Res Clin Pract. 2021 Jan;171:108586. [7] A cohort study of antihypertensive use during pregnancy in South Korea, 2013-2017. Pregnancy Hypertens. 2020 Oct;22:167-174. [8] The Association of Pregnancy-induced Hypertension with Bronchopulmonary Dysplasia - A Retrospective Study Based on the Korean Neonatal Network database. Sci Rep. 2020 Mar 27;10(1):5600. [9] Genetic Associations of Circulating Cardiovascular Proteins With Gestational Hypertension and Preeclampsia. JAMA Cardiol. 2024 Mar 1;9(3):209-220.