A pandemic within a pandemic: Diabetes, gestational diabetes, and vitamin B12 deficiency in pregnant women during the COVID-19 era

Abstract

Background: The coronavirus disease 2019 (COVID-19) pandemic has significantly worsened health outcomes in pregnant women, a population already vulnerable due to physiological immune suppression and increased insulin resistance. Gestational diabetes mellitus (GDM) and vitamin B12 deficiency further compound these risks, creating a complex and potentially dangerous clinical picture. Aim: This review examines the interrelationships between COVID-19, GDM, and vitamin B12 deficiency in pregnancy, and evaluates the clinical implications for maternal and fetal health. Methods: A narrative review of the current literature was conducted, focusing on the mechanisms linking severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, GDM, vitamin B12 metabolism, metformin use, and nutritional status during pregnancy. Results: SARS-CoV-2 directly damages pancreatic beta cells and triggers hyperinflammation, disrupting glycemic control in pregnant women. Vitamin B12 deficiency elevates homocysteine levels, impairing insulin signaling and promoting thrombosis, thereby increasing risks of GDM, preeclampsia, and adverse fetal neurodevelopmental outcomes. Metformin, widely used in GDM and polycystic ovary syndrome (PCOS) management, further reduces B12 absorption. Pandemic-related disruptions to antenatal care, food access, and psychosocial stress accelerated B12 depletion in this population. The Mediterranean diet offers partial mitigation, though targeted supplementation remains necessary in high-risk individuals. Conclusion: Routine B12 screening should be integrated into standard antenatal care, particularly for women with GDM, PCOS, or long-term metformin use. Relevance for patients: Pregnant women with GDM or PCOS using metformin are at heightened risk of vitamin B12 deficiency, which can silently harm both mother and baby. Regular B12 monitoring and timely supplementation are simple, safe, and potentially life-changing interventions.

Keywords

COVID-19 / Gestational diabetes / Vitamin B12 deficiency / Pregnancy / Metformin / Mediterranean diet / Homocysteine / SARS-CoV-2

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