Red blood cell distribution width in pregnancy: a systematic review

Anisocytosis has been associated with the severity and prognosis of several acute and chronic diseases, as well as physiological conditions such as pregnancy. Anisocytosis is quantified by the red blood cell distribution width (RDW), expressed as the ratio, multiplied by 100, between the standard deviation (SD) of red blood cell volumes and the mean corpuscular volume, or as the SD of erythrocyte volumes (RDW-SD). The aim of the present review was to report the state of the art on the physiological values and the putative diagnostic and prognostic roles of RDW in complicated pregnancy. Literature research for articles published in the last ten years was conducted in Pubmed, Web of Science, ClinicalTrials.gov, and Scopus databases. Abstracts were independently screened by two investigators. If relevant, full articles were retrieved. References, in these articles, citing relevant reviews or original studies were also accessed to identify additional eligible studies. Any disagreement between the reviewers was resolved by a third investigator. A total of 28 studies were included in the review. These studies reported changes in RDW values during physiological pregnancy, and associations between the RDW and several pregnancy complications including anaemia, preeclampsia, gestational diabetes, and recurrent miscarriage. This review provides background information for establishing physiological and pathological RDW values in pregnancy for diagnostic and prognostic use in clinical practice.