In the past decade, consistent evidence has been reported on supplemental folic acid use for the prevention of neural tube defects.1–4 This has led national health authorities in the Netherlands in 1992 and 1993 and worldwide to recommend periconceptional folic acid intake and to initiate various campaigns to promote its use. Media activities, women's magazines, leaflets, and information added to oral contraceptives and provided by health care workers have contributed to increased knowledge and adequate folic acid intake.5,6 However, the impact of such efforts is disappointing considering that 50–97% of women planning pregnancy are still not taking folic acid in the recommended period (4 weeks before until 8 weeks after conception) or do not take supplements at all.7–11 Poor compliance has led to folate fortification of foods in different countries to increase folate status, though this policy has not been implemented in most European countries including the Netherlands. In addition, consumption of extra folate as natural food folates has been shown to be ineffective in optimizing folate status.12 This dependence on supplemental folic acid to improve periconceptional folate status emphasizes the need for a stronger, or possibly an alternative, approach to reach a larger group of women.
A prepregnancy consultation is an ideal opportunity to address the use of folic acid among the target population and may be more effective than large population-based campaigns. Instead of assessing reported folic acid intake to ascertain compliance, measuring blood folate concentrations to determine long-term folate status may be more reliable because women who do not follow the recommendation could feel guilty and may give biased answers. As part of a study on preconception counseling in the Netherlands, we evaluated whether periconceptional folic acid supplementation recommendation has a positive effect on folate status of women planning pregnancy. Therefore, we chose to question supplement use only before counseling and to evaluate changes in folate concentrations in blood to assess compliance after intervention. Furthermore, folate status of women already taking supplements was evaluated biochemically to assess whether they continue to use supplements, regardless of time until pregnancy. Red cell folate was chosen as the primary outcome measure of this study because it represents tissue stores and, therefore, more accurately reflects long-term folate status than does serum folate.13
MATERIALS AND METHODS
Between September 1997 and April 1999, couples with a scheduled appointment at the fertility clinic (because of the inability to become pregnant within 1 year) or at the clinic for preconception care (because of previous obstetric complications or other maternal risk factors) of the University Medical Center Nijmegen were approached by letter to take part in a study on preconception counseling. After giving their informed consent, 193 couples were invited for participation of which 186 couples attended the first intake visit. Because of pregnancy, 18 women were excluded, which resulted in 168 women eligible for participation in this study. The Medical Ethical Committee of the University Medical Center Nijmegen approved the study.
Before the first visit to the outpatient department (the intake visit), couples were asked to complete a Dutch version of the Preconceptional Health Assessment form developed by Cefalo and Moos,14 which includes a section on folic acid or other vitamin use. Based on the answers obtained from this questionnaire, women were categorized as reported “users” or “nonusers” of supplements before counseling. A physician verified the responses given in the questionnaire during the intake visit to assess prepregnancy risk factors. After 4–6 weeks, the counseling visit took place, at which time relevant aspects of health promotion were discussed, including smoking cessation, nutritional habits, antenatal care, and folic acid supplement intake. All women were advised to start taking a tablet of Matrilon daily, a multivitamin supplement containing 400 μg of folic acid, until 8 weeks after conception. They were provided with the supplements so that they could start the same day. Women who reported using folic acid already were encouraged to continue doing so, and also received a supply of Matrilon to last until the next visit. Blood samples for the analysis of red cell and serum folate levels were taken at the intake and counseling visits to assess folate status before advice to start or continue folic acid supplementation (precounseling folate status), and then every 3–4 months after counseling and in the 6th, 8th, and 12th week of pregnancy. The longest follow-up was 18 months.
Blood samples were drawn in ethylenediaminetetraacetic acid vacutainer tubes and centrifuged within 2 hours for 10 minutes at 3000 × g. Plasma was separated and stored at −35C until analysis. Hematocrit was measured, and whole blood was diluted five-fold with sodium ascorbate (1 g per 100 mL) and stored at −35C. Folate concentrations in red cells and serum were determined using the IMx Folic Acid Assay, based on the Microparticle Enzyme Immunoassay technology for the IMx immunoassay system (Abbott Laboratories, North Chicago, IL). The hemolysates were further diluted with IMx Folate RBC Lysis Reagent (Abbott Laboratories, North Chicago, IL). The intra-assay coefficients of variation for means of duplicate measurements were between 3% and 6%, and the interassay coefficients of variation for different pools of serum ranged from 6% to 10%.
Two linear mixed models for repeated measurements were used to analyze the change in folate status among the study population (ie, at 4 months and 1 year after counseling, respectively). In both models, a fixed linear relation with time after counseling was postulated, as well as individual random linear coefficients. The first model was used for analysis of red cell folate changes among initial nonusers of supplements after a time period of 4 months, corresponding with the duration of erythropoiesis and incorporation of folate in maturing red cells. The second model included all red cell measurements up to 1 year after counseling and was used to interpret long-term compliance of initial supplement users. Because a linear increase in folate concentrations is not expected after the incorporation of supplemental folic acid in maturing erythrocytes, this second model was not considered applicable to women who were not using supplements before counseling as this could result in unrealistically high estimated red cell levels. Additionally, changes in serum folate were analyzed using both models.
An indicator variable to discriminate between reported users and nonusers of supplements before counseling was used, and another determinant based on precounseling folate status was added to the model. Though studies on folate status have reported a vast range in folate levels after various interventions,15–22 values were evaluated that would discriminate between users and nonusers. Because of the impossibility to give normative data on red cell and serum folate levels before and/or after folic acid supplementation, we assumed supplement use using cutoff levels assessed in the 2-month intervention study of 500 μg of folic acid daily previously carried out at our department.14 Folate concentrations of greater than or equal to 590 nmol/L in red cells and greater than or equal to 20 nmol/L in serum were found in all supplemented nonpregnant healthy women (n = 49) at the same laboratory in a similar setting.14
Folate status of men joining their partners at the counseling and following visits were also analyzed after 4 months as well as after 1 year, using the two previously described models. Because men were not counseled to take supplements, red cell folate data were entered into the 4-month as well as the 1-year model, thereby not accounting for the time necessary for incorporation of supplemental folic acid into red cells. Finally, blood samples taken at the intake and at the counseling visit (to determine precounseling folate status) were compared using the Wilcoxon signed-rank test. All analyses were carried out using version 6.12 of the SAS package (SAS Institute Inc., Cary, NC). P < .05 was considered statistically significant.
Among the 168 eligible women, 23 withdrew between the intake and the counseling visit, 33 were lost to follow-up, and one participant was excluded because of missing precounseling data. This resulted in 111 women (66%) with multiple sample data for further analysis (77 women from the fertility clinic and 34 women from the preconception care clinic). Of these women, 63 became pregnant over the course of the study period. The age of participants ranged from 25 to 42 years, with a mean age (standard deviation) of 32.5 (3.5) years. Demographic characteristics were obtained from the Preconceptional Health Assessment form and are shown in Table 1.
Folate concentrations measured in samples collected at the counseling visit were chosen to represent the precounseling folate status of the study population. Estimated red cell folate levels at the intake and counseling visits did not differ significantly (P = .285). Therefore, it is very unlikely that women already started to use folic acid during the period between the two visits. The number of women in which the folate status after 4 months was evaluated (n = 97) is slightly lower than the number that was evaluated over the 1-year period (n = 111). This results from an interval longer than 4 months between the counseling visit and the subsequent sampling visit(s) in 14 cases. In 138 counseling consultations, the partner was present, and follow-up of 98 men was achieved.
A total of 62 women (56%) indicated in the Preconceptional Health Assessment form that they were not using folic acid supplements. Among women who were biochemically evaluated after 4 months, 52 (54%) were reported nonusers of supplemental folic acid. As measured in red cells, folate status of these reported nonusers improved significantly 4 months after they were encouraged to start folic acid-containing supplementation (Table 2). In the analysis based on cutoff values, an even higher increase in red cell folate was seen among women with precounseling folate levels below 590 nmol/L. Estimated red cell folate levels of these assumed nonusers of supplements were comparable with those of initial reported nonusers 4 months after counseling, 689 nmol/L and 680 nmol/L, respectively. Red cell folate concentrations of 49 women (44%) reporting supplement use before counseling did not change significantly over time (Table 3). Women with precounseling folate levels above 590 nmol/L (assumed supplement users) also maintained this folate status after 1 year.
Estimated serum folate levels between 18.0 nmol/L and 23.9 nmol/L were found for all groups after counseling (Tables 2 and 3). No significant change was seen among initial reported nonusers after 4 months or after 1 year. Women with low precounseling serum folate levels improved significantly both after 4 months as well as 1 year after counseling. However, significantly lower estimated serum folate levels were found at both time points among women reporting supplement use as well as those with high precounseling folate levels.
Before counseling, folate status in men was lower than in all groups of women (Table 4). Mean estimated red cell folate levels did, however, improve significantly after 1 year.
This study reveals that a single preconceptional consultation appears to be an appropriate way to emphasize the importance of periconceptional folic acid and to improve the use of a folic acid-containing supplement among the target population. Furthermore, women encouraged to keep taking folic acid continue to do so. It is unlikely that supplement use changed in the 6-week interval between intake and counseling because red cell folate levels did not differ significantly between both visits.
Although folate levels were considered to reflect compliance, we should emphasize the meaning of low and high folate levels. A discrepancy exists in that 12 of the 47 women claiming to use folic acid at intake (26%) had a red cell folate concentration below 590 nmol/L, and 16 of the 60 women who indicated not using supplements (27%) had a red cell folate concentration above 590 nmol/L. It is possible that folate levels between the supplement users and nonusers overlap,21 and that a subset of women have just started using supplements and have not yet reached this red cell folate level. Although we can only speculate, it is also likely that some women falsely claim to use supplements.
The decline in serum folate levels among users of supplements and participants with high baseline serum levels is not in accordance with red cell folate data and cannot be explained. However, it has been reported that serum and red blood cell measurements of folate can be inconsistent as well as that serum levels only reflect transient folate concentrations between absorption and use or storage and are less accurate in determining true folate status than red cell levels.2
We did not study the influence of factors confounding folate status such as the methylenetetrahydrofolate reductase polymorphisms, chronic illnesses, use of antifolates, and nutritional intake. It was remarkable that though men were not advised to take supplements, their overall folate status improved over the course of the study. This may be attributed to an increased intake of dietary folate, as the importance of proper nutrition before and during pregnancy was also stressed during the counseling consultation. Although dietary changes may contribute to the improvement in folate status among women as well, the substantially higher folate levels of women as compared with the male population cannot be explained by diet alone. As enrichment of foods with folate is not allowed in the Netherlands, the only plausible source of folic acid that can explain this increase among the target group is by the supplements.
Most studies on the knowledge and use of folic acid supplements in populations of women of reproductive age conclude that awareness of its protective effect in the prevention of neural tube defects is greater than proper intake. A gap as large as 76% of women aware versus only 16% of women taking it before pregnancy was found in an Irish population.23 Considering that 51% of women in that study did take supplements once pregnant, it may not be clear that intake should be started preconceptionally and should, therefore, receive greater emphasis.
Several reasons why some women still did not take folic acid despite being aware of its benefits have been documented in previous studies among Dutch women and include a long time period between trying to conceive and actual pregnancy or forgetting to take them.4 Perhaps Dutch women consider folic acid as a drug and, therefore, hesitate to take it. This is in contrast to a study among Irish women, which illustrated that many women, had they received counseling on periconceptional folic acid, would be willing to take supplements and would prefer a pill to food fortification.8 Whereas in some populations compliance seems to be the major problem, in other populations awareness has not even been achieved. In a Canadian population of women, only 1.8% had the specific knowledge that neural tube defects could be prevented with folic acid supplementation.11 A study among Israeli women demonstrated that only 5.5% of them had heard about folic acid, and 2.8% reported to have taken it.10 Although knowledge and proper use of supplements is quite high in the Dutch population as compared with other parts of the world,4,5 we need to continue efforts to increase its intake among the target group.
Our study population consisted of couples attending our outpatient clinic. Although they may be somewhat more motivated to use folate than the population at large, addressing periconceptional folic acid use during a prepregnancy visit now has been shown to have a positive effect on folate status. Considering the additional benefits, including the opportunity to discuss other aspects of good health before pregnancy, application and expansion of preconception care should be considered to promote the message on the primary prevention of neural tube defects and other aspects of health promotion.
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© 2002 by The American College of Obstetricians and Gynecologists. Published by Wolters Kluwer Health, Inc. All rights reserved.
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