Association of catechol-o-methyltransferase gene polymorphism with preeclampsia and biomarkers of oxidative stress: Study protocol for a prospective case-control study in Pakistan

儿茶酚-O-甲基转移酶基因多态性与先兆子痫及氧化应激生物标志物的关联：巴基斯坦一项前瞻性病例对照研究的研究方案