Did iron deficiency during pregnancy actually cause fetal sex reversal? Nature study reveals developmental code
Cambridge team confirms that iron ions are required to drive SRY gene expression, and that maternal iron deficiency may trigger ovarian development in male embryos. I. Reversal of cognition: abnormal sex development in an iron-deficient environment In June 2025, Nature published a breakthrough study from the National Institute of Genetics, Japan: Experimental design: Pregnant mice received a low-iron diet (iron content reduced to 40% of normal) during the critical period for sex determination (equivalent to 5-12 weeks of human pregnancy) Amazing sex reversal: 5 out of 72 XY chromosome mice developed ovarian tissue (4 were fully feminized, and 1 formed an ovary-testis chimera) Molecular mechanism: inactivation of the iron-dependent enzyme KDM3A → silencing of the SRY gene → termination of testis developmental program Developmental biologist Dr. James Wilson of the University of Oxford paraphrases, “SRY is the ‘ignition switch’ for male development, and the ferrous ion (Fe²⁺) is the key that activates this switch. When maternal iron reserves are depleted, XY embryos may shift to the female developmental pathway.” II. The Global Status of Iron Deficiency: the Neglected Crisis of Pregnancy 1 Epidemiology of iron deficiency in Asian pregnant women shore anemia rate Characteristics of high-risk groups East Asian 38.2% 12% higher in rural than urban areas Southeast Asia 45.7% Vegetarian pregnant women have a 3-fold increased risk southern Asia 52.1% High prevalence among those with <2 years between second births (Source: WHO 2025 Global Nutrition Report) 2. The hidden dangers of iron deficiency Early symptoms: fatigue, hair loss, inattention (often mistaken for “normal pregnancy reactions”) Diagnostic pitfalls: normal hemoglobin ≠ iron sufficiency! Serum ferritin <30μg/L suggests deficiency Window period specificity: fetal gender differentiation occurs in early pregnancy, while traditional iron supplementation begins in mid-pregnancy – too late! III. Lifelong imprinting of iron status on offspring: beyond gender reversal ▶…
