Hyperemesis gravidarum (HG), severe nausea and vomiting in pregnancy, can lead to vitamin deficiencies. Little is known about HG-related vitamin K deficiency. We aimed to summarise available evidence on the occurrence of HG-related vitamin K deficiency and corresponding maternal and neonatal complications. A systematic review was conducted, searching Medline and EMBASE from inception to 12 November 2020. We identified 1564 articles, of which we included fifteen in this study: fourteen case reports (n 21 women) and one retrospective cohort study (n 109 women). Nine out of twenty-one women reported in case reports had a prolonged prothrombin time (PT). The cohort study measured PT in 39/109 women with HG, of whom 10/39 women (26 %) had prolonged PT. In total, 30–50 % women received vitamin K supplementation after vitamin K deficiency had been diagnosed. Four case reports (n 4 women) reported corresponding maternal complications, all consisting of coagulopathy-related haemorrhage. Nine case reports (n 16 neonates) reported corresponding neonatal complications including intracranial haemorrhage (n 2 neonates) and embryopathy (n 14 neonates), which consisted of Binder phenotype (n 14 neonates), chondrodysplasia punctata (n 9 neonates) and grey matter heterotopia (n 3 neonates). In conclusion, vitamin K deficiency and related complications occur among women with HG. In our systematic review, we were unable to assess the incidence rate.
