In a 2014 study, women with adequate levels of vitamin B12 and folic acid, were found to be more resistant to the detrimental effects of the environmental pollutant DDT and therefore and lower risk of early pregnancy loss.
Measuring B12 status can be done through blood testing, however, there is controversy as to whether a normal serum B12 level is indicative of a normal tissue B12 level. Urinary Methylmelonic Acid is considered to be a better test for this or an organic acid test, which identifies imbalances before any abnormal findings on a CBC or blood work. Organic acid testing can indicate the functional need for specific nutrients, diet modification, antioxidant protection, detoxification, and other therapies.
Source: F. Ouyang, M. P. Longnecker, S. A. Venners, S. Johnson, S. Korrick, J. Zhang, X. Xu, P. Christian, M.-C. Wang, X. Wang. Preconception serum 1,1,1-trichloro-2,2,bis(p-chlorophenyl)ethane and B-vitamin status: independent and joint effects on women’s reproductive outcomes. American Journal of Clinical Nutrition, 2014; 100 (6): 1470 DOI: 10.3945/ajcn.114.088377