RBC Folate and Serum Folate, Vitamin B-12, and Homocysteine in Chinese Couples Prepregnancy in the Shanghai Preconception Cohort

The protective effects of maternal folate on neural tube defects are well-established. Emerging evidence has shown paternal folate also is related to pregnancy outcome and offspring health. This study aimed to assess the status of red blood cell (RBC) folate and serum folate, vitamin B-12, and homocysteine (Hcy) and their associated factors in a cohort of pregnancy-preparing couples. This was a cross-sectional study involving 14,178 participants from the extension of the Shanghai Preconception Cohort conducted in 2018–2021. Circulating biomarker concentrations were measured, and the prevalence of abnormal status was reported. Linear and logistic regression analyses were conducted to examine associations of demographic factors (age, education, and income), lifestyle factors (smoking, drinking, and folic acid supplement use), and BMI with concentrations of the folate-related biomarkers, abnormal status of folate (deficiency and insufficiency) and vitamin B-12 (deficiency and marginal deficiency), and hyperhomocysteinemia. The geometric mean (95% CI) concentrations of RBC folate, serum folate, vitamin B-12, and Hcy were 490 nmol/L (485, 496 nmol/L), 20.1 nmol/L (19.8, 20.3 nmol/L), 353 pmol/L (350, 357 pmol/L), and 7.54 μmol/L (7.48, 7.60 μmol/L) in females, respectively, and 405 nmol/L (401, 409 nmol/L), 13.5 nmol/L (13.4, 13.7 nmol/L), 277 pmol/L (274, 279 pmol/L), and 12.0 μmol/L (11.9, 12.2 μmol/L) in males, respectively. Prevalence of abnormal status was higher in males than females for the 4 folate-related biomarkers: RBC folate deficiency (<340 nmol/L, 32.2% compared with 18.9%), serum folate deficiency (<10.0 nmol/L, 26.5% compared with 7.3%), RBC folate insufficiency (<906 nmol/L, 96.6% compared with 90.1%), serum folate insufficiency (<15.9 nmol/L, 65.5% compared with 31.4%), vitamin B-12 marginal deficiency (148–221 pmol/L, 21.4% compared with 8.8%), and hyperhomocysteinemia (>15.0 μmol/L, 22.1% compared with 2.5%). Most pregnancy-preparing couples failed to achieve the optimal RBC folate status (>906 nmol/L) as recommended by the WHO. These findings call for attention to the insufficiency status of folate and promising strategies to improve the folate status of the pregnancy-preparing population not exposed to folic acid fortification.