Preeclampsia is one of the leading causes of maternal and neonatal mortality and morbidity worldwide, affecting 2–8% of all pregnancies. Studies suggest a link between complement activation and preeclampsia. The complement system plays an essential role in the innate immunity, leading to opsonization, inflammation, and elimination of potential pathogens. The complement system also provides a link between innate and adaptive immunity and clearance of immune complexes and apoptotic cells. During pregnancy there is increased activity of the complement system systemically. However, locally at the placenta, complement inhibition is crucial for the maintenance of a normal pregnancy. Inappropriate or excessive activation of the complement system at the placenta is likely involved in placental dysfunction, and is in turn associated with pregnancy complications like preeclampsia. Therefore, modulation of the complement system could be a potential therapeutic target to prevent pregnancy complications such as preeclampsia. This review, based on a systematic literature search, gives an overview of the complement system and its activation locally in the placenta and systemically during healthy pregnancies and during complicated pregnancies, with a focus on preeclampsia. Furthermore, this review describes results of animal and human studies with a focus on the complement system in pregnancy, and the role of the complement system in placental dysfunction. Various clinical and animal studies provide evidence that dysregulation of the complement system is associated with placental dysfunction and therefore with preeclampsia. Several drugs are used for prevention and treatment of preeclampsia in humans and animal models, and some of these drugs work through complement modulation. Therefore, this review further discusses these studies examining pharmaceutical interventions as treatment for preeclampsia. These observations will help direct research to generate new target options for prevention and treatment of preeclampsia, which include direct and indirect modulation of the complement system.

子痫前症是全世界孕产妇和新生儿死亡率和发病率的主要原因之一，影响所有妊娠的2–8％。研究表明补体激活与先兆子痫之间存在联系。补体系统在先天免疫中起着至关重要的作用，导致调理作用，炎症和消除潜在病原体。补体系统还提供了先天性和适应性免疫与免疫复合物和凋亡细胞清除之间的联系。在怀孕期间，全身补体的活性增加。但是，在胎盘局部，补体抑制对于维持正常妊娠至关重要。胎盘功能异常可能与胎盘补体系统的不适当或过度激活有关，继而与子痫前期等妊娠并发症相关。因此，调节补体系统可能是预防妊娠并发症如先兆子痫的潜在治疗靶标。这项综述基于系统的文献检索，概述了补胎系统及其在胎盘中以及系统地在健康妊娠和复杂妊娠期间的全身激活，重点是先兆子痫。此外，本综述描述了动物和人体研究的结果，重点是妊娠中的补体系统以及补体系统在胎盘功能障碍中的作用。各种临床和动物研究均提供证据，证明补体系统功能异常与胎盘功能异常有关，因此与先兆子痫有关。几种药物用于预防和治疗人和动物模型中的先兆子痫，其中一些药物通过补体调节起作用。因此，本综述进一步讨论了这些研究，探讨了将药物干预作为先兆子痫的治疗方法。这些观察将有助于直接研究，以产生预防和治疗先兆子痫的新目标方案，包括直接和间接调节补体系统。