1. Frey, HA & Klebanoff, MA (2016) The epidemiology, etiology, and costs of preterm birth. Semin Fetal Neonatal Med 21, 68–73.
2. Bailey, LB & Gregory, JF 3rd (1999) Folate metabolism and requirements. J Nutr 129, 779–782.
3. Smits, LJ & Essed, GG (2001) Short interpregnancy intervals and unfavourable pregnancy outcome: role of folate depletion. Lancet 358, 2074–2077.
4. Zhu, BP (2005) Effect of interpregnancy interval on birth outcomes: findings from three recent US studies. Int J Gynecol Obstet 89, Suppl. 1, S25–S33.10.1016/j.ijgo.2004.08.002
5. Moussa, HN, Hosseini Nasab, S, Haidar, ZA et al. (2016) Folic acid supplementation: what is new? Fetal, obstetric, long-term benefits and risks. Future Sci OA 2, FSO116.
6. Pfeiffer, CM, Johnson, CL, Jain, RB et al. (2007) Trends in blood folate and vitamin B-12 concentrations in the United States, 1988 2004. Am J Clin Nutr 86, 718–727.
7. Crider, KS, Bailey, LB & Berry, RJ (2011) Folic acid food fortification – its history, effect, concerns, and future directions. Nutrients 3, 370–384.
8. Tinker, SC, Hamner, HC, Qi, YP et al. (2015) US women of childbearing age who are at possible increased risk of a neural tube defect-affected pregnancy due to suboptimal red blood cell folate concentrations, National Health and Nutrition Examination Survey 2007 to 2012. Birth Defects Res A Clin Mol Teratol 103, 517–526.
9. Czeizel, AE, Dudas, I, Vereczkey, A et al. (2013) Folate deficiency and folic acid supplementation: the prevention of neural-tube defects and congenital heart defects. Nutrients 5, 4760–4775.
10. Blom, HJ (2009) Folic acid, methylation and neural tube closure in humans. Birth Defects Res A Clin Mol Teratol 85, 295–302.
11. Smithells, RW, Sheppard, S, Schorah, CJ et al. (1980) Possible prevention of neural-tube defects by periconceptional vitamin supplementation. Lancet 1, 339–340.
12. Bibbins-Domingo, K, Grossman, DC, Curry, SJ et al. (2017) Folic acid supplementation for the prevention of neural tube defects: US Preventive Services Task Force Recommendation Statement. JAMA 317, 183–189.
13. Shaw, GM, Carmichael, SL, Nelson, V et al. (2004) Occurrence of low birthweight and preterm delivery among California infants before and after compulsory food fortification with folic acid. Public Health Rep 119, 170–173.
14. Scholl, TO, Hediger, ML, Schall, JI et al. (1996) Dietary and serum folate: their influence on the outcome of pregnancy. Am J Clin Nutr 63, 520–525.
15. Scholl, TO & Johnson, WG (2000) Folic acid: influence on the outcome of pregnancy. Am J Clin Nutr 71, 5 Suppl., 1295S–1303S.
16. Siega-Riz, AM, Savitz, DA, Zeisel, SH et al. (2004) Second trimester folate status and preterm birth. Am J Obstet Gynecol 191, 1851–1857.
17. Bodnar, LM, Himes, KP, Venkataramanan, R et al. (2010) Maternal serum folate species in early pregnancy and risk of preterm birth. Am J Clin Nutr 92, 864–871.
18. Bukowski, R, Malone, FD, Porter, FT et al. (2009) Preconceptional folate supplementation and the risk of spontaneous preterm birth: a cohort study. PLoS Med 6, e1000061.
19. Dunlop, AL, Taylor, RN, Tangpricha, V et al. (2012) Maternal micronutrient status and preterm versus term birth for black and white US women. Reprod Sci 19, 939–948.
20. Shaw, GM, Carmichael, SL, Yang, W et al. (2011) Periconceptional intake of folic acid and food folate and risks of preterm delivery. Am J Perinatol 28, 747–752.10.1055/s-0031-1280855
21. Raghavan, R, Riley, AW, Volk, H et al. (2017) Maternal multivitamin intake, plasma folate and vitamin B12 levels and autism spectrum disorder risk in offspring. Paediatr Perinat Epidemiol 32, 100–111.
22. Surkan, PJ, Dong, L, Ji, Y et al. (2017) Paternal involvement and support and risk of preterm birth: findings from the Boston Birth Cohort. J Psychosom Obstet Gynaecol. . doi: 10.1080/0167482X.2017.1398725.
23. Wang, X, Zuckerman, B, Pearson, C et al. (2002) Maternal cigarette smoking, metabolic gene polymorphism, and infant birth weight. JAMA 287, 195–202.10.1001/jama.287.2.195
24. Blumenfeld, YJ, El-Sayed, YY, Lyell, DJ et al. (2015) Risk factors for prolonged postpartum length of stay following cesarean delivery. Am J Perinatol 32, 825–832.
25. Organisation for Economic Co-operation and Development (2014) Average Length of Stay: Childbirth 2014/1. Paris: OECD Publishing.
26. Greenberg, JA & Bell, SJ (2011) Multivitamin supplementation during pregnancy: emphasis on folic acid and l-methylfolate. Rev Obstet Gynecol 4, 126–127.
27. Huo, Y, Li, J, Qin, X et al. (2015) Efficacy of folic acid therapy in primary prevention of stroke among adults with hypertension in China: the CSPPT randomized clinical trial. JAMA 313, 1325–1335.
28. World Health Organization (2015) Serum and Red Blood Cell Folate Concentrations for Assessing Folate Status in Populations. Geneva: WHO.
29. Wang, S, Ge, X, Zhu, B et al. (2016) Maternal continuing folic acid supplementation after the first trimester of pregnancy increased the risk of large-for-gestational-age birth: a population-based birth cohort study. Nutrients 8, 493.10.3390/nu8080493
30. Chanarin, I, Rothman, D, Ward, A et al. (1968) Folate status and requirement in pregnancy. Br Med J 2, 390–394.10.1136/bmj.2.5602.390
31. McNulty, B, McNulty, H, Marshall, B et al. (2013) 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 98, 92–98.
32. Hamilton, BE, Martin, JA, Osterman, MJ et al. (2017) Births: Provisional Data for 2016. Vital Statistics Rapid Release Report no. 2. Hyattsville, MD: National Center for Health Statistics.
33. Cheng, TL, Mistry, KB, Wang, G et al. (2018) Folate nutrition status in mothers of the Boston Birth Cohort, sample of a US urban low-income population. Am J Public Health 108, 799–807.10.2105/AJPH.2018.304355
34. Behrman, RE & Butler, AS (editors) (2007) Preterm Birth: Causes, Consequences, and Prevention. Washington, DC: National Academies Press.
35. Johnson, WG, Scholl, TO, Spychala, JR et al. (2005) Common dihydrofolate reductase 19-base pair deletion allele: a novel risk factor for preterm delivery. Am J Clin Nutr 81, 664–668.10.1093/ajcn/81.3.664
36. Chen, LW, Lim, AL, Colega, M et al. (2015) Maternal folate status, but not that of vitamins B-12 or B-6, is associated with gestational age and preterm birth risk in a multiethnic Asian population. J Nutr 145, 113–120.
37. Bergen, N, Jaddoe, V, Timmermans, S et al. (2012) Homocysteine and folate concentrations in early pregnancy and the risk of adverse pregnancy outcomes: the Generation R Study. BJOG 119, 739–751.
38. Cunningham, F, Leveno, K, Bloom, S et al. (2004) Williams Obstetrics, 24th ed. New York: McGraw-Hill Education/Medical.
39. Courtemanche, C, Elson-Schwab, I, Mashiyama, ST et al. (2004) Folate deficiency inhibits the proliferation of primary human CD8+T lymphocytes in vitro. J Immunol 173, 3186–3192.
40. Zhao, M, Chen, YH, Dong, XT et al. (2013) Folic acid protects against lipopolysaccharide-induced preterm delivery and intrauterine growth restriction through its anti-inflammatory effect in mice. PLoS One 8, e82713.
41. Ananth, CV & Vintzileos, AM (2006) Epidemiology of preterm birth and its clinical subtypes. J Matern Fetal Neonatal Med 19, 773–782.
42. Farrell, C-JL, Kirsch, SH & Herrmann, M (2013) Red cell or serum folate: what to do in clinical practice? Clin Chem Lab Med 51, 555–569.
43. Szklo, M & Nieto, FJ (2014) Epidemiology: Beyond the Basics. Burlington, MA: Jones & Bartlett Publishers.
44. Saccone, G, Sarno, L, Roman, A et al. (2016) 5-Methyl-tetrahydrofolate in prevention of recurrent preeclampsia. J Matern Fetal Neonatal Med 29, 916–920.
45. Yang, QH, Carter, HK, Mulinare, J et al. (2007) Race-ethnicity differences in folic acid intake in women of childbearing age in the United States after folic acid fortification: findings from the National Health and Nutrition Examination Survey, 2001–2002. Am J Clin Nutr 85, 1409–1416.
46. Ahluwalia, IB & Daniel, KL (2001) Are women with recent live births aware of the benefits of folic acid? MMWR Recomm Rep 50, 3–14.
47. Higgins, JR, Quinlivan, EP, McPartlin, J et al. (2000) The relationship between increased folate catabolism and the increased requirement for folate in pregnancy. BJOG 107, 1149–1154.
48. Wang, G, Hu, FB, Mistry, KB et al. (2016) Association between maternal prepregnancy body mass index and plasma folate concentrations with child metabolic health. JAMA Pediatr 170, e160845.
49. Wang, H, Mueller, NT, Li, J et al. (2017) Association of maternal plasma folate and cardiometabolic risk factors in pregnancy with elevated blood pressure of offspring in childhood. Am J Hypertens 30, 532–540.
50. Wiens, D & DeSoto, M (2017) Is high folic acid intake a risk factor for autism? – A review. Brain Sci 7, 149.