Mast cell activation syndrome in pregnancy, delivery, postpartum and lactation: a narrative review

Mast cell activation syndrome (MCAS) is a chronic multisystem disease of aberrant constitutive and reactive mast cell mediator release causing generally inflammatory, allergic, and dystrophic issues. The pathobiology of MCAS drives extraordinary clinical complexity and heterogeneity, which led to only recent recognition despite increasingly apparent substantial prevalence, perhaps as high as 17%. It also has a strong female predilection. Thus, MCAS inescapably impacts pregnancy and the post-partum period in many women. No specific research in the pregnant or post-partum MCAS population has been performed yet. However, its prevalence and potential for driving substantial morbidity merit obstetric providers' acquaintance with this illness and its potential impacts on their patients during pregnancy, delivery, the post-partum period, and lactation. Extensive literature review across all medical specialities, plus direct experience in the authors' practices, provides guidance in recognising MCAS in pregnancy and diagnosing and effectively managing it. Described herein are manners in which MCAS, a protean multisystem disease, adversely affects all stages of pregnancy and post-partum. In order to reduce risks of MCAS causing complications before, during and after pregnancy, identifying and controlling the syndrome prior to pregnancy is best, but, even if the disease is not recognised until late, there may still be opportunities to mitigate its effects. There is precedent for improved outcomes if comorbid MCAS is recognised and controlled. This review provides the first comprehensive guide for obstetric providers regarding this emerging major comorbidity.