Pregnancy Salt Substitution Trial for Hypertensive Disorders of Pregnancy Prevention (PREG-Salt)

Inclusion Criteria: 1. Singleton pregnancy with a viable fetus at ≤16 weeks of gestation. 2. Meets at least one of the following criteria (enrolled sequentially): 1. Systolic Blood Pressure (SBP) ≥130 mmHg and \<160 mmHg at enrollment, OR current monotherapy with antihypertensive medications such as labetalol or nifedipine (priority enrollment). 2. At least one of the following 4 items: advanced maternal age (≥35 years), pre-pregnancy obesity (BMI ≥28 kg/m²), history of preeclampsia, or pre-existing type 1 or type 2 diabetes. 3. At least two of the following 5 items: history of adverse pregnancy outcome (e.g., fetal death, placental abruption, fetal growth restriction), personal history of gestational hypertension or family history of preeclampsia (mother or sister), history of gestational diabetes, obstructive sleep apnea, or pre-pregnancy overweight (BMI 24-28 kg/m²). 3. Routinely eats at least two meals per day at home (including meals brought from home). 4. Able to attend regular antenatal check-ups and is expected to complete the study follow-up. 5. Provides written informed consent. - Exclusion Criteria: 1. SBP ≥160 mmHg or Diastolic Blood Pressure (DBP) ≥110 mmHg at enrollment. 2. Conditions or history associated with high uterine tension (e.g., polyhydramnios, macrosomia, hydatidiform mole); autoimmune diseases (e.g., systemic lupus erythematosus, antiphospholipid syndrome). 3. History of chronic kidney disease, OR any antenatal check-up with a confirmed estimated Glomerular Filtration Rate (eGFR) \<70 ml/min/1.73m², OR dipstick urine protein ≥2+. 4. Diagnosed hyperkalemia. 5. History of hypotension or syncope. 6. A household member who shares meals has a confirmed diagnosis of chronic kidney disease or hyperkalemia.