Many maternal immune cells populate the decidua, which is the mucosal lining of the uterus transformed during pregnancy. Here, abundant natural killer (NK) cells and macrophages help the uterine vasculature adapt to fetal demands for gas and nutrients, thereby supporting fetal growth. Fetal trophoblast cells budding off the forming placenta and invading deep into maternal tissues come into contact with these and other immune cells. Besides their homeostatic functions, decidual NK cells can respond to pathogens during infection, but in doing so, they may become conflicted between destroying the invader and sustaining fetoplacental growth. We review how maternal NK cells balance their double duty both in the local microenvironment of the uterus and systemically, during toxoplasmosis, influenza, cytomegalovirus, malaria and other infections that threat pregnancy. We also discuss recent developments in the understanding of NK-cell responses to SARS-Cov-2 infection and the possible dangers of COVID-19 during pregnancy.

许多母体免疫细胞居住在蜕膜中，蜕膜是怀孕期间转变的子宫粘膜内层。在这里，丰富的自然杀伤（NK）细胞和巨噬细胞帮助子宫脉管系统适应胎儿对气体和营养的需求，从而支持胎儿的生长。胎儿滋养层细胞从正在形成的胎盘中萌芽并深入母体组织，与这些和其他免疫细胞接触。除了其稳态功能外，蜕膜 NK 细胞还可以在感染过程中对病原体做出反应，但在此过程中，它们可能会在消灭入侵者和维持胎儿胎盘生长之间发生冲突。我们回顾了在弓形虫病、流感、巨细胞病毒、疟疾和其他威胁妊娠的感染期间，母体 NK 细胞如何在子宫局部微环境和全身系统中平衡其双重职责。我们还讨论了 NK 细胞对 SARS-Cov-2 感染反应的最新进展以及怀孕期间 COVID-19 的可能危险。