Although there is accumulating evidence regarding the additional protective effect of folic acid against adverse pregnancy outcomes other than neural tube defects, these effects have not been elucidated in detail. We evaluated whether folic acid supplementation is associated with favorable maternal and fetal outcomes. This was a secondary analysis of 215 pregnant women who were enrolled in our prior study. With additional data from telephone interviews regarding prenatal folic acid supplementation, existing demographic, maternal and fetal data were statistically analyzed. The concentration of folic acid in maternal blood was significantly higher following folic acid supplementation (24.6 ng/mL vs.11.8 ng/mL). In contrast, homocysteine level in maternal blood decreased with folic acid supplementation (5.5 µmol/mL vs. 6.8 µmol/mL). The rates of both preeclampsia (odds ratio [OR], 0.27; 95% confidence interval [CI], 0.09–0.76) and small for gestational age (SGA; 9.2% vs. 20.0%; OR, 0.42; 95% CI, 0.18–0.99) were lower in the folic acid supplementation group than those in the control group. Other pregnancy outcomes had no association with folic acid supplementation. The findings indicate that folic acid supplementation may help to prevent preeclampsia and SGA. Further studies are warranted to elucidate the favorable effects of folic acid supplementation on pregnancy outcomes.
Citation: Kim MW, Ahn KH, Ryu K-J, Hong S-C, Lee JS, Nava-Ocampo AA, et al. (2014) Preventive Effects of Folic Acid Supplementation on Adverse Maternal and Fetal Outcomes. PLoS ONE 9(5): e97273. https://doi.org/10.1371/journal.pone.0097273
Editor: Saeed Dastgiri, Tabriz University of Medical Sciences, Iran (Republic of Islamic)
Received: August 18, 2013; Accepted: April 17, 2014; Published: May 19, 2014
Copyright: © 2014 Kim et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Funding: This study was supported by grant No. K1220211 from Korea University College of Medicine and a grant (2012-0003134) from the National Research Foundation of Korea funded by the Ministry of Education, Science and Technology. harmacological Research and Applied Solutions– PharmaReasons provided support in the form of a salary for author AANO, but did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. The specific roles of these authors are articulated in the ‘author contributions’ section.
Competing interests: AANO is an employee of Pharmacological Research and Applied Solutions–PharmaReasons. There are no patents, products in development or marketed products to declare. This does not alter the authors’ adherence to all the PLOS ONE policies on sharing data and materials.
Overwhelming evidence supports the use of folic acid supplementation during pregnancy to prevent neural tube defects . Prenatal intake of folic acid has also been associated with better long-term neurodevelopment in offspring . However, whether the protective effects of folic acid extend to other pregnancy outcomes have not been clearly identified . In a population-based prospective cohort study, maternal hyperhomocysteinemia was linked to a higher risk of adiposity and type 2 diabetes in mothers  and their offspring .
Our prior study showed that lower folate and higher homocysteine concentrations in maternal serum at the time of delivery are associated with unfavorable pregnancy outcomes such as pre-term birth and pre-eclampsia . In this study, we determined whether antenatal folic acid supplementation is associated with favorable maternal and fetal outcomes.
Materials and Methods
This was a retrospective secondary analysis to a study group described previously . We obtained the approval of the Institutional Review Board in Korea University Anam Hospital (IRB No: ED12248). This study was exempt from participants’ informed consent because the investigator conducting research of this secondary analysis did not obtain information about research subjects via an interaction with them, nor did the investigator obtain identifiable private information. Briefly, the study population included women with singleton pregnancies who delivered at the Korea University Anam Hospital between June 1, 2009, and June 13, 2010 and provided informed consent. Maternal blood samples were collected during antenatal visits or upon admission to the hospital. Cord blood samples were obtained from the umbilical vein immediately after delivery. Plasma total homocysteine concentration was measured using an automated enzymatic assay and homocysteine methyltransferase and d-amino acid oxidase (Toshiba 200FR-NEO Auto Analyzer; Toshiba Medical Systems Co., Ltd., Tokyo, Japan). Folate level was measured using an iodine-125-based radioimmunoassay (Cobra II 5010; Packard, Meriden, CT, USA). Among a total of 227 pregnant women reviewed initially, 215 cases were included in the study. Continuous variables are expressed as mean ± standard deviation or median (interquartile range [IQR]) values, whereas categorical variables are presented using their absolute values and percentages. Student’s t-test or the Wilcoxon rank-sum test was used for continuous variables; and the chi-square test or Fisher’s exact test were used for categorical variables. We performed a multivariable logistic regression analysis to analyze the associations between folic acid supplementation with other confounding factors such as parity, familial monthly income, preeclampsia, somatic classification of newborns. All statistical analyses were performed using SAS ver. 9.3 software (SAS Institute, Cary, NC, USA), and statistical significance was defined as a two-tailed P<.05.
We found no significant differences between the two groups regarding maternal age, body mass index, alcohol drinking history, smoking history, economic status, or occupational status. Median parity was 1 (IQR, 0–1) in the women who did not take a folic acid supplement and 0 (IQR, 0–1) in the supplementation group (Table 1). The concentration of folic acid in maternal blood was significantly higher with folic acid supplementation (24.6 ng/mL [14.4–37.0] vs. 11.8 ng/mL [7.4–18.5]; P<.0001). In contrast, homocysteine level in maternal blood decreased with folic acid supplementation (5.5 µmol/mL [3.9–8.0] vs. 6.8 µmol/mL [4.9–9.7]; P = .0163). The incidence of preeclampsia was lower in the folic acid supplementation group than that in the control group (4.2% vs. 14.1%; P = .0076). With the folic acid supplementation, the rate of small for gestational age was decreased. No differences were observed between the two groups concerning the rates of gestational diabetes, placenta previa, placental abruption, preterm births, or birth weight (Table 2). We performed multivariate logistic regression analysis after adjusting for confounding factors, which included parity, familial monthly income, preeclampsia and prenatal intake of folic acid. Based on these analyses, the risk of preeclampsia decreased with folic acid supplementation (odds ratio [OR], 0.27; 95% confidence interval [CI], 0.09–0.76; P = .014; Table 3). The risk of small for gestational age (SGA) was also lowered by folic acid intake (OR = 0.42; 95% CI = 0.18–0.99; P = .0047; Tables 4). Higher parity was associated with lower SGA (OR = 0.41; 95% CI = 0.19–0.89; P = .0023).
In our study, folic acid supplementation decreased the risk of small for gestational age. It is known that folic acid plays a role in both placental development and fetal growth, as it contributes to protein, lipid, and DNA synthesis. Folate contains a methyl group, and it can affect DNA methylation by altering 1-carbon metabolism. The epigenetic regulation of growth processes through folic acid supplementation may contribute to embryonic development and fetal growth . In this theoretical framework, folic acid has been reported to be positively related to intrauterine fetal growth –. In a population-based prospective study, the Generation R Study, birth weight was 68 g higher in women who started folic acid supplementation preconceptionally and 53 g higher in those who started after pregnancy recognition compared with the birth weight for mothers who did not take folic acid supplements . In contrast, homocysteine has been reported to be inversely related to placental and fetal growth . Considering that the homocysteine level was lower in the folic acid supplementation group, the association between folic acid level and birth weight would be affected directly or indirectly by the folate-homocysteine pathway.
In our study, the concentration of folic acid was elevated and the homocysteine level decreased significantly in women with history of folic acid supplementation. These findings inform that the study pregnant women followed their physician’s recommendations well, so they should be encouraged to consume folic acid or informed about its beneficial role. It is well known that fewer than 20% of women comply with folic acid supplementation during early pregnancy, and more than half of pregnancies are unintended or unplanned , . Moreover, there is variability in the recommended amount and duration of folic acid supplementation between countries and clinicians. Under this circumstance, the necessity of mandatory folate fortification or consensus guideline is critical , . In our study, according to the folic acid supplementation policy of our hospital (women in good health status consume a multivitamin containing folic acid (0.4–1.0 mg) daily for at least 2–3 months before conception and throughout pregnancy and the postpartum period), most women in the supplementary group were taking folic acid at the time of blood sampling. Considering the additional protective effect of folic acid against adverse pregnancy outcomes, folic acid supplementation should be recommended throughout pregnancy.
The relationship between folic acid and various pregnancy outcomes such as preeclampsia, placental abruption, abortion, preterm birth, and stillbirth has been investigated –, however, the results are still controversial. Some studies have demonstrated that folic acid prevents adverse pregnancy outcomes, whereas others have failed to confirm these favorable effects , –. Regarding the preterm birth, we demonstrated in our previous study the relationship between folate concentrations and preterm delivery , however in the current secondary analysis of that study we failed to elucidate an association between folic acid supplementation and the rate of preterm birth.
The largest study to report the protective effect of folic acid supplementation against preterm birth was conducted by Bukowski et al. . In a secondary analysis of the FASTER trial, they described that preconceptional folic acid supplementation for 1 year or longer is associated with a 70% decrease in the risk of spontaneous preterm delivery at 20–28 weeks and a 50% decrease in the risk of spontaneous preterm delivery at 28–32 weeks compared with no supplementation. The differing results between that study and our study are believed to be due to the rate of preterm birth in the study population. They reported that 2660 women (7.7%) delivered prematurely before 37 weeks, and spontaneous preterm births before 37 weeks were reported for 1658 women (4.8%). Conversely, the rates of preterm birth in our study were 41.2% in the group without supplementation and 43.7% in the folic acid supplementation group. This high incidence of preterm birth is attributed to the fact that the patient population in our institution primarily consisted of high-risk patients who transferred from other local hospitals. Thus, the high-risk status of the patients might have diluted the effect of folic acid supplementation. In contrast, as we previously reported an association between folic acid concentration and the rate of preterm birth, this difference may also have arisen from the duration of folic acid supplementation. We did not consider the duration of supplementation, and this is a limitation of our study.
Accumulating evidence indicates the role of folic acid in fetal development and placentation , . Folic acid plays a physiological role in cell proliferation and DNA replication. If folic acid concentration is low in maternal blood, plasma homocysteine levels are elevated as a consequence. Folic acid may be involved in trophoblastic invasion during the early stage of placental development . Homocysteine, a metabolite of the amino acid methionine, is an independent risk factor for cardiovascular disease because of its adverse effects on endothelial function , . Because preeclampsia is regarded as a systematic vascular disease arising from maternal endothelial dysfunction, hyperhomocysteinemia may contribute to the incidence of preeclampsia . In this context, folic acid supplementation could decrease the prevalence of preeclampsia, as demonstrated in many studies, including ours , –. In particular, considering the vegetable-rich diet of the Korean population, this finding caused us to reevaluate the merits of folic acid supplementation. It was recently suggested that hyperhomocysteinemia alone does not sufficiently cause preeclampsia. In an animal study, no increase in the incidence of hypertension or proteinuria was observed in methylenetetrahydrofolate reductase-deficient mice. However, a low-folate diet was associated with proteinuria and growth restriction. These findings may highlight, along with our result, the importance of folic acid on pregnancy outcomes . Lastly, our result showed that higher parity is associated with lower SGA. It is consistent with the results of other studies where primiparity is an independent risk factor for SGA , .
Concerning the study’s limitations, this was an observational study conducted in a tertiary care hospital; thus, the findings may not be representative of the general population. Nonetheless, our data from reliable statistical analyses are clinically meaningful to present information about the association between folic acid supplementation and various pregnancy outcomes.
The data indicate that folic acid supplementation may be helpful in reducing the incidence of preeclampsia and SGA. To clarify the optimal amount and duration of folic acid supplementation for improving pregnancy outcomes, further studies are warranted.
This study was supported by grant No. K1220211 from Korea University College of Medicine and a grant (2012-0003134) from the National Research Foundation of Korea funded by the Ministry of Education, Science and Technology.
Conceived and designed the experiments: MWK SCH. Performed the experiments: MWK SCH. Analyzed the data: KHA JSL AANO MJO HJK KJR. Contributed reagents/materials/analysis tools: JSL MWK. Wrote the paper: MWK KHA SCH.
- 1. De-Regil LM, Fernandez-Gaxiola AC, Dowswell T, Pena-Rosas JP (2010) Effects and safety of periconceptional folate supplementation for preventing birth defects. Cochrane database of systematic reviews (Online). (10): CD007950
- 2. Christian P, Murray-Kolb LE, Khatry SK, Katz J, Schaefer BA, et al. (2010) Prenatal micronutrient supplementation and intellectual and motor function in early school-aged children in Nepal. JAMA: the journal of the American Medical Association. 304(24): 2716–23
- 3. Chiaffarino F, Ascone GB, Bortolus R, Mastroia-Covo P, Ricci E, et al.. (2010) [Effects of folic acid supplementation on pregnancy outcomes: a review of randomized clinical trials]. Minerva ginecologica. 62(4): 293–301. PubMed PMID: 20827247.
- 4. Krishnaveni GV, Hill JC, Veena SR, Bhat DS, Wills AK, et al. (2009) Low plasma vitamin B12 in pregnancy is associated with gestational ‘diabesity’ and later diabetes. Diabetologia. 52(11): 2350–8
- 5. Yajnik CS, Deshpande SS, Jackson AA, Refsum H, Rao S, et al. (2008) Vitamin B12 and folate concentrations during pregnancy and insulin resistance in the offspring: the Pune Maternal Nutrition Study. Diabetologia. 51(1): 29–38
- 6. Kim MW, Hong SC, Choi JS, Han JY, Oh MJ, et al. (2012) Homocysteine, folate and pregnancy outcomes. Journal of obstetrics and gynaecology: the journal of the Institute of Obstetrics and Gynaecology. 32(6): 520–4
- 7. Steegers-Theunissen RP, Obermann-Borst SA, Kremer D, Lindemans J, Siebel C, et al. (2009) Periconceptional Maternal Folic Acid Use of 400 µg per Day Is Related to Increased Methylation of the IGF2 Gene in the Very Young Child. PLoS ONE 4(11): e7845
- 8. Scholl TO, Hediger ML, Schall JI, Khoo CS, Fischer RL (1996) Dietary and serum folate: their influence on the outcome of pregnancy. The American journal of clinical nutrition. 63(4): 520–5. PubMed PMID: 8599315.
- 9. Iyengar L, Rajalakshmi K (1975) Effect of folic acid supplement on birth weights of infants. Am J Obstet Gynecol. 122(3): 332–6. PubMed PMID: 1130456.
- 10. Goldenberg RL, Tamura T, Cliver SP, Cutter GR, Hoffman HJ, et al.. (1992) Serum folate and fetal growth retardation: a matter of compliance? Obstet Gynecol. 79(5 (Pt 1)): 719–22. PubMed PMID: 1565355.
- 11. Timmermans S, Jaddoe VW, Hofman A, Steegers-Theunissen RP, Steegers EA (2009) Periconception folic acid supplementation, fetal growth and the risks of low birth weight and preterm birth: the Generation R Study. The British journal of nutrition. 102(5): 777–85
- 12. van der Molen EF, Verbruggen B, Novakova I, Eskes TK, Monnens LA, et al.. (2000) Hyperhomocysteinemia and other thrombotic risk factors in women with placental vasculopathy. BJOG: an international journal of obstetrics and gynaecology. 107(6): 785–91. PubMed PMID: 10847236.
- 13. Scott J (2011) Folic acid consumption throughout pregnancy: differentiation between trimesters. Ann Nutr Metab. 59(1): 46–9
- 14. Lane IR (2011) Preventing neural tube defects with folic acid: nearly 20 years on, the majority of women remain unprotected. Journal of obstetrics and gynaecology: the journal of the Institute of Obstetrics and Gynaecology. 31(7): 581–5
- 15. Colapinto CK, O’Connor DL, Dubois L, Tremblay MS (2012) Folic acid supplement use is the most significant predictor of folate concentrations in Canadian women of childbearing age. Appl Physiol Nutr Metab. 37(2): 284–92
- 16. McNulty B, Pentieva K, Marshall B, Ward M, Molloy AM, et al. (2011) Women’s compliance with current folic acid recommendations and achievement of optimal vitamin status for preventing neural tube defects. Hum Reprod. 26(6): 1530–6
- 17. Burke G, Robinson K, Refsum H, Stuart B, Drumm J, et al.. (1992) Intrauterine growth retardation, perinatal death, and maternal homocysteine levels. The New England journal of medicine. 326(1): 69–70. PubMed PMID: 1727072.
- 18. Steegers-Theunissen RP, Boers GH, Blom HJ, Trijbels FJ, Eskes TK (1992) Hyperhomocysteinaemia and recurrent spontaneous abortion or abruptio placentae. Lancet. 339(8801): 1122–3. PubMed PMID: 1349147.
- 19. Vollset SE, Refsum H, Irgens LM, Emblem BM, Tverdal A, et al.. (2000) Plasma total homocysteine, pregnancy complications, and adverse pregnancy outcomes: the Hordaland Homocysteine study. The American journal of clinical nutrition. 71(4): 962–8. PubMed PMID: 10731504.
- 20. Wouters MG, Boers GH, Blom HJ, Trijbels FJ, Thomas CM, et al.. (1993) Hyperhomocysteinemia: a risk factor in women with unexplained recurrent early pregnancy loss. Fertility and sterility. 60(5): 820–5. PubMed PMID: 8224267.
- 21. Bukowski R, Malone FD, Porter FT, Nyberg DA, Comstock CH, et al. (2009) Preconceptional folate supplementation and the risk of spontaneous preterm birth: a cohort study. PLoS medicine. 6(5): e1000061
- 22. Czeizel AE, Puho EH, Langmar Z, Acs N, Banhidy F (2010) Possible association of folic acid supplementation during pregnancy with reduction of preterm birth: a population-based study. Eur J Obstet Gynecol Reprod Biol. 148(2): 135–40
- 23. Charles DH, Ness AR, Campbell D, Smith GD, Whitley E, et al. (2005) Folic acid supplements in pregnancy and birth outcome: re-analysis of a large randomised controlled trial and update of Cochrane review. Paediatr Perinat Epidemiol. 19(2): 112–24
- 24. Solanky N, Requena Jimenez A, D’Souza SW, Sibley CP, Glazier JD (2010) Expression of folate transporters in human placenta and implications for homocysteine metabolism. Placenta. 31(2): 134–43
- 25. Mislanova C, Martsenyuk O, Huppertz B, Obolenskaya M (2011) Placental markers of folate-related metabolism in preeclampsia. Reproduction. 142(3): 467–76
- 26. Williams PJ, Bulmer JN, Innes BA, Broughton Pipkin F (2011) Possible roles for folic acid in the regulation of trophoblast invasion and placental development in normal early human pregnancy. Biology of reproduction. 84(6): 1148–53
- 27. McNulty H, Pentieva K, Hoey L, Ward M (2008) Homocysteine, B-vitamins and CVD. Proc Nutr Soc. 67(2): 232–7
- 28. McDowell IF, Lang D (2000) Homocysteine and endothelial dysfunction: a link with cardiovascular disease. J Nutr. 130(2S Suppl): 369S–72S. PubMed PMID: 10721909.
- 29. Wang J, Trudinger BJ, Duarte N, Wilcken DE, Li Wang X (2000) Elevated circulating homocyst(e)ine levels in placental vascular disease and associated pre-eclampsia. BJOG: An International Journal of Obstetrics & Gynaecology. 107(7): 935–8
- 30. Dekker GA, de Vries JI, Doelitzsch PM, Huijgens PC, von Blomberg BM, et al.. (1995) Underlying disorders associated with severe early-onset preeclampsia. Am J Obstet Gynecol. 173(4): 1042–8. PubMed PMID: 7485291.
- 31. Rajkovic A, Mahomed K, Malinow MR, Sorenson TK, Woelk GB, et al.. (1999) Plasma homocyst(e)ine concentrations in eclamptic and preeclamptic African women postpartum. Obstet Gynecol. 94(3): 355–60. PubMed PMID: 10472859.
- 32. Wen SW, Chen XK, Rodger M, White RR, Yang Q, et al.. (2008) Folic acid supplementation in early second trimester and the risk of preeclampsia. Am J Obstet Gynecol. 198(1): 45 e1–7. doi: 10.1016/j.ajog.2007.06.067. PubMed PMID: 18166303.
- 33. Falcao S, Bisotto S, Gutkowska J, Lavoie JL (2008) Hyperhomocysteinemia is not sufficient to cause preeclampsia in an animal model: the importance of folate intake. Am J Obstet Gynecol. 200(2): 198 e1–5. doi: 10.1016/j.ajog.2008.10.003. PubMed PMID: 19110222.
- 34. Cnattingius S, Forman MR, Berendes HW, Graubard BI, Isotalo L (1993) Effect of age, parity, and smoking on pregnancy outcome: a population-based study. Am J Obstet Gynecol. Jan; 168(1 Pt 1): 16–21. PubMed PMID: 8420320.
- 35. Shoham-Vardi I, Leiberman JR, Kopernik G (1994) The association of primiparity with intrauterine growth retardation. Eur J Obstet Gynecol Reprod Biol. Feb; 53(2): 95–101. ubMed PMID: 8194656.