为明确硫酸镁是否有助于预防轻度先兆子痫进行随机对比研究。轻度先兆子痫的诊断标准:问隔6 h以上2次收缩压≥140 mmHg(1 mmHg=0.133 kPa),或舒张压≥90 mmHg,合并近期发生蛋白尿(≥1+)至少2次。慢性高血压和重度先兆子痫均除外。重度先兆子痫为:2次收缩压≥160mmHg、或舒张压≥110 mmHg,或24 h尿蛋白≥5 g,或持续头痛、视力 To determine whether magnesium sulfate helps prevent mild preeclampsia in a randomized controlled study. Diagnostic criteria for mild preeclampsia: Ask 2 systolic blood pressure ≥140 mmHg (1 mmHg = 0.133 kPa) every 6 hours or diastolic blood pressure ≥90 mmHg, combined with the recent occurrence of proteinuria (≥1 +) at least 2 times. Except for chronic hypertension and severe preeclampsia. Severe preeclampsia: 2 systolic blood pressure ≥ 160 mmHg, or diastolic blood pressure ≥ 110 mmHg, or 24 h urinary protein ≥ 5 g, or persistent headache, visual acuity