[1] Pfeiffer CM, Sternberg MR, Schleicher RL, Haynes BMH, Rybak ME, Pirkle JL. The CDC’s Second National Report on Biochemical Indicators of Diet and Nutrition in the U.S. Population is a valuable tool for researchers and policy makers. J Nutr 2013;143(6):938s − 47s. http://dx.doi.org/10.3945/jn.112.172858CrossRef
[2] Du YJ, Li J, Wang HL, Du JY, Qu PF, Zhang R, et al. Epidemiological characteristics of serum vitamin B12 and folate levels in women awaiting delivery. Chin J Epidemiol 2020;41(8):1359 − 64. http://dx.doi.org/10.3760/cma.j.cn112338-20190927-00707 (In Chinese). CrossRef
[3] Bulloch RE, McCowan LME, Thompson JMD, Houghton LA, Wall CR. Plasma folate and its association with folic acid supplementation, socio-demographic and lifestyle factors among New Zealand pregnant women. Br J Nutr 2019;122(8):910 − 8. http://dx.doi.org/10.1017/S0007114519001788CrossRef
[4] Marchetta CM, Hamner HC. Blood folate concentrations among women of childbearing age by race/ethnicity and acculturation, NHANES 2001-2010. Matern Child Nutr 2016;12(1):39 − 50. http://dx.doi.org/10.1111/mcn.12134CrossRef
[5] Zhu L, Ling H. National neural tube defects prevention program in China. Food Nutr Bull 2008;29(2 Suppl):S196 − 204. http://dx.doi.org/10.1177/15648265080292S123CrossRef
[6] Liu JF, Jin L, Meng QQ, Gao LL, Zhang L, Li ZW, et al. Changes in folic acid supplementation behaviour among women of reproductive age after the implementation of a massive supplementation programme in China. Public Health Nutr 2015;18(4):582 − 8. http://dx.doi.org/10.1017/S1368980014000950CrossRef
[7] McNulty B, McNulty H, Marshall B, Ward M, Molloy AM, Scott JM, et al. Impact of continuing folic acid after the first trimester of pregnancy: findings of a randomized trial of folic acid supplementation in the second and third trimesters. Am J Clin Nutr 2013;98(1):92 − 8. http://dx.doi.org/10.3945/ajcn.112.057489CrossRef
[8] Looman M, Geelen A, Samlal RAK, Heijligenberg R, Gunnewiek JMTK, Balvers MGJ, et al. Changes in micronutrient intake and status, diet quality and glucose tolerance from preconception to the second trimester of pregnancy. Nutrients 2019;11(2):460. http://dx.doi.org/10.3390/nu11020460CrossRef
[9] Dubois L, Diasparra M, Bédard B, Colapinto CK, Fontaine-Bisson B, Morisset AS, et al. Adequacy of nutritional intake from food and supplements in a cohort of pregnant women in Québec, Canada: the 3D Cohort Study (Design, Develop, Discover). Am J Clin Nutr 2017;106(2):541 − 8. http://dx.doi.org/10.3945/ajcn.117.155499CrossRef
[10] Xie QR, Fu SL, Guo F, Zhu YY, Su PY. Blood folic acid concentration and seasonal variations among progestational and pregnant women. Mod Prev Med 2015;42(1): 61-3, 71. http://d.wanfangdata.com.cn/periodical/xdyfyx201501021. (In Chinese). http://d.wanfangdata.com.cn/periodical/xdyfyx201501021
[11] Cheng TL, Mistry KB, Wang GY, Zuckerman B, Wang XB. Folate nutrition status in mothers of the boston birth cohort, sample of a US urban low-income population. Am J Public Health 2018;108(6):799 − 807. http://dx.doi.org/10.2105/ajph.2018.304355CrossRef