Article 1 B12 deficiency 1 Carbon 1 Estradiol 1 Female 1 Folic Acid 1 Homocysteine 1 Humans 1 Menstrual Cycle 1 Pregnancy 1 S-Adenosylmethionine 1 Vitamin B 12 1 ademetionine carbon 1 carbon metabolism 1 computer model 1 concentration (parameter) 1 contraceptive agent 1 controlled study 1 cyanocobalamin 1 cystathionine beta synthase 1 dihydrofolate reductase 1 enzyme inhibition 1 enzyme substrate 1 estradiol 1 female 1 folic acid 1 folic acid deficiency 1 glutathione 1 homeostasis 1