Figure. Flowchart of participants.
Liu J, Mei Z, Ye R, Serdula MK, Ren A, Cogswell ME. Micronutrient supplementation and pregnancy outcomes double-blind randomized controlled trial in China.. JAMA Intern Med.. Published online January 7, 2013. doi: 10.1001/jamainternmed.2013.1632.
eMethods 1. Supplement formulations
eMethods 2. Data collection procedures
eMethods 3. Outcome definitions
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Liu J, Mei Z, Ye R, Serdula MK, Ren A, Cogswell ME. Micronutrient Supplementation and Pregnancy Outcomes: Double-Blind Randomized Controlled Trial in China. JAMA Intern Med. 2013;173(4):276–282. doi:10.1001/jamainternmed.2013.1632
Author Affiliations: Institute of Reproductive and Child Health/Ministry of Health Key Laboratory of Reproductive Health and Department of Epidemiology and Biostatistics, School of Public Health, Peking University Health Science Center, Beijing, China (Drs Liu, Ye, and Ren); and Division of Nutrition, Physical Activity, and Obesity, National Center for Chronic Disease Prevention and Health Promotion, Centers for Disease Control and Prevention, Atlanta, Georgia (Drs Mei, Serdula, and Cogswell).
Background Beyond perinatal folic acid supplementation, the need for additional prenatal prophylaxis of iron with or without other micronutrients remains unclear. We aim to investigate the maternal and infant health effects of iron plus folic acid and multiple micronutrient supplements vs folic acid alone when provided to pregnant women with no or mild anemia.
Methods In this randomized double-blind controlled trial, 18 775 nulliparous pregnant women with mild or no anemia were enrolled from 5 counties of northern China from May 2006 through April 2009. Women were randomly assigned to daily folic acid (400 μg) (control), folic acid–iron (30 mg), or folic acid, iron, and 13 additional vitamins and minerals provided before 20 weeks gestation to delivery. Primary outcome was perinatal mortality. Secondary outcomes included neonatal and infant mortality, preterm delivery, birth weight, birth length, gestational duration, and maternal hemoglobin concentration and anemia.
Results A total of 92.7% of women consumed 80% to 100% of supplements as instructed. On average, women consumed 177 supplements. Compared with daily prenatal folic acid, supplementation with iron–folic acid with or without other micronutrients did not affect the rate of perinatal mortality (8.8, 8.7, and 8.3, respectively) per 1000 births, and relative risks (RRs) were 1.00 (95% CI, 0.68-1.46; P = .99) and 0.94 (95% CI, 0.64-1.39; P = .76), respectively. Risk of other adverse maternal and infant outcomes also did not differ, except that RRs for third-trimester maternal anemia were 0.72 (95% CI, 0.63-0.83; P < .001) and 0.71 (95% CI, 0.62-0.82; P < .001), respectively.
Conclusion Prenatal iron–folic acid and other micronutrient supplements provided to Chinese women with no or mild anemia prevented later pregnancy anemia beyond any benefit conferred by folic acid alone but did not affect perinatal mortality or other infant outcomes.
Trial Registration clinicaltrials.gov Identifier: NCT00133744
About 3 million stillbirths and 3 million early neonatal deaths occurred worldwide in 2004, 98% of which were in less developed countries.1 A high perinatal mortality rate was reported in rural China in 2000.2 Potential preventable causes of stillbirths and early neonatal deaths are maternal anemia and related micronutrient deficiencies.3Quiz Ref IDAside from perinatal folic acid supplements to prevent neural tube defects, multiple health organizations recommend pregnant women routinely receive iron–folic acid supplements to prevent anemia.4 Meta-analyses of randomized controlled trials (RCTs) indicate that daily prenatal iron–folic acid supplementation prevents iron deficiency and anemia.5,6 The effect of prenatal iron–folic acid supplementation on perinatal mortality and other maternal and infant outcomes remains unclear, particularly among nonanemic women. Thus, some question the added benefit of prophylactic iron supplementation.7
In some settings, other micronutrient deficiencies may limit the effectiveness of prenatal iron–folic acid supplementation,8,9 leading to trials to determine the maternal and infant health effects conferred from additional multiple micronutrients (MMN) vs iron–folic acid alone.10,11 In 2005, only 2 trials of iron–folic acid vs MMN supplements had been published, but neither was adequately powered to examine perinatal morality. A study in Xian, China,12 used cluster randomization to examine birth weight as the primary outcome; the amount of iron in the iron–folic acid supplement was 60 mg vs 30 mg in the MMN supplement. It was unknown if this higher dose of iron would affect the comparison owing to either increased gastrointestinal effects or interactions with other nutrients. In recent meta-analyses, provision of MMN supplements vs iron–folic acid improved mean birth weight and reduced the risk of low birth weight but did not benefit birth length, head circumference, or the duration of gestation.13,14 The effects of MMN supplements on fetal and infant deaths were inconsistent15-22 and may have been modified by maternal baseline nutrition.23
China is a country in nutrition transition.24 In China, 29% of pregnant women were anemic in 2002.25 In southeast China, prenatal anemia prevalence declined by more than 50% between 1993 and 2005.26 With the exception of periconceptional folic acid, prenatal iron and other micronutrients are not routinely prescribed or used by nonanemic women. Similarly, in the United States and other industrialized countries, there are conflicting recommendations about use of prophylactic iron with or without other nutrients.7
The objective of the current study is to investigate the maternal and infant health effects of iron–folic acid and MMN supplements vs iron–folic acid alone when provided to pregnant women with no or mild anemia. We hypothesized that prenatal iron–folic acid supplements with or without other micronutrients, given from the first prenatal visit through delivery, would reduce perinatal mortality beyond any reductions conferred by iron–folic acid alone.
The trial took place nearby Beijing in 5 rural counties in Hebei Province, China, where basic health services were provided through 3-tier (county, township, and village) health care networks. Village clinics and township hospitals provided basic prenatal health care services, and county hospitals provided delivery service. Health facility and service capacity were similar in 5 counties, and the same guidelines or procedures for prenatal health care and delivery were used. The population at the time of the study was about 2.5 million, and gross domestic product per capita about $4700.
Eligible pregnant women were enrolled from May 2006 through April 2009 and individually randomized in a 1:1:1 ratio to receive a daily supplement containing folic acid, iron–folic acid, or MMN from early pregnancy through delivery. The study protocol was approved by the institutional review boards of the Centers for Disease Control and Prevention, Atlanta, Georgia, and Peking University, Beijing, China, and renewed annually.
To be eligible, pregnant women (1) recorded dates of their menstruation for 2 or more months before they became pregnant, (2) were nulliparous, (3) were at least 20 years old, (4) were not more than 20 weeks gestation, (5) were legally competent, (6) had not consumed micronutrient supplements other than folic acid in the prior 6 months, (7) had a hemoglobin (Hb) level greater than 10.0 g/dL, (8) resided in and received prenatal care in 1 of 5 counties, and (9) consented to participate. (To convert Hb to grams per liter, multiply by 10.0.)
Before the study started, the project was publicized in each participating county using pamphlets, posters, radio, and television. During the first prenatal visit, the consent form was read to each woman by a physician trained in informed consent procedures. After the woman provided verbal consent, the form was signed by the physician plus a witness.
Randomization was stratified by county, and random block sizes of 3, 6, and 9 were used to ensure geographical balance with an approximately equal distribution of treatments within and across study counties. A statistician external to the study randomly assigned ten 4-digit lot numbers to each of the 3 supplement types (masked to the formulation and allocation) and generated the assignment list for each county proportional to the expected number of participants; within each county and block, lot numbers were randomly assigned using RANUNI in SAS statistics software (SAS Institute Inc). Aside from a pharmaceutical engineer who ensured allocation of lot numbers to the correct supplement formulations, all others (ie, participants, local physicians, study personnel, and investigators) were masked to the identity of the supplements. Treatment codes were broken after completion of the study and main analyses.
At enrollment, the physician assigned women the next lot number on the randomization schedule. Each woman received 2 bottles of supplements at enrollment and 1 at monthly follow-up visits. Each bottle contained 31 supplements, including 1 of the supplements (see eMethods 1 for supplement formulations) according to lot number. The capsules were of the same size, color, and shape, and bottles were identical except for the lot number. Study participants were instructed to take 1 supplement daily from enrollment until delivery. Supplements were provided at no cost; otherwise, no compensation was given for participation.
Trained county or township physicians completed relevant measurements and collected data based on a perinatal and child health care surveillance system (see eMethods 2 for detailed data collection procedures). To ensure data quality, Peking University staff conducted various training programs, performed monthly site supervisions, and cross-checked all death events. The primary outcome was perinatal mortality. Secondary outcomes included neonatal deaths, infant deaths, maternal Hb concentration and anemia at 24 to 28 weeks of gestation, birth weight, birth length, duration of gestation, and preterm delivery. (Outcome definitions are provided in eMethods 3.)
The estimated perinatal mortality rate was 16 per 1000 births in the folic acid group based on our previous study.27 A 40% reduction in the iron–folic acid group compared with the folic acid group and a 50% reduction in the MMN group were hypothesized based on various observational studies.28-32 With a 2-sided significance level of P = .05, β-error specification of 0.20, and correction for continuity, 5272 per group were needed to detect a 40% reduction in the iron–folic acid group compared with the folic acid group and a 50% reduction in the MMN group compared with the iron–folic acid group. To account for the estimated 4.7% of women lost to follow-up, 4.2% of dropouts, and 4.0% of nonadherence,27 6280 women per group were needed. The statistical power was expected to be adequate for outcomes with a higher baseline prevalence (ie, low birth weight, preterm birth, and maternal anemia).
Multiple pregnancies were excluded from analyses. The denominator for perinatal mortality was live births plus stillbirths. The denominator for other study outcomes was live births. We defined mean compliance as the number of supplements consumed divided by the number of days from enrollment to birth; the number of supplements consumed was estimated from the number of supplements remaining in the bottle at each return visit.
All analyses were based on an intent-to-treat principle. All randomized women with a known birth outcome were included in analyses irrespective of compliance. We examined the distribution of key baseline characteristics among the 3 groups using χ2 tests for categorical variables and analysis of variance for continuous. χ2 Tests and independent sample t tests were used to test the differences in dichotomous and continuous outcomes between supplement groups (iron–folic acid vs folic acid, MMN vs folic acid, and MMN vs iron–folic acid), respectively. Unadjusted relative risks (RRs) with 95% confidence intervals (CIs) were calculated for mortality, low birth weight, preterm birth, and maternal anemia. Rate differences with 95% CIs were also calculated for mortality; a number needed to treat with 95% CIs was calculated for outcomes with statistical significance. Unadjusted mean differences with 95% CIs were calculated for continuous outcomes. The Data Safety Monitoring Board met 4 times during the study and reviewed 3 interim analyses by supplement group masked to allocation, in which the significance levels began lower and ended at the final analysis close to the prespecified overall significance level.33 All P values were 2-sided, and statistical significance was set at P = .05 for the final analysis without adjustment for multiple comparisons. We used SAS statistical software (version 9; SAS Institute Inc) for all analyses.
Among the 18 963 pregnant women considered for enrollment, 120 refused to participate in the study, and 68 were not eligible (Figure). Of the 18 775 women randomized, 28 moved, 33 dropped out, 2 died during pregnancy (1 from a traffic accident and 1 from autoimmune disease), and 815 had spontaneous or induced abortions. Of the 17 897 remaining women with known pregnancy outcomes (95.3%), 17 830 women (99.6%) had singleton pregnancies; 17 748 ended their pregnancy with live births, 82 with stillbirths. Among the live births, 71 early neonatal deaths, 87 neonatal deaths, and 134 infant deaths were identified. Of the 87 neonatal deaths, 24 died of asphyxia, 23 of premature birth, 15 had birth defects, 9 had pneumonia, and 16 died of other or unknown causes. The number of women having multiple pregnancies were not statistically different across the treatment groups (P = .30) (Figure).
The baseline characteristics were balanced across supplement groups (Table 1). The mean (SD) maternal age, gestation at enrollment, and Hb level were 23.7 (2.9) years, 11.9 (4.6) weeks, and 12.5 (1.0) g/dL, respectively. Almost all participants were of Han ethnicity, 1.6% had primary or less education, and 90.8% were farmers. About 5% to 6% of women had Hb concentrations of 10.0 to 10.9 g/dL.
Adherence to the assigned supplements was high, and only 20 women reported having taken additional micronutrient supplements including calcium, iron, zinc, or MMNs. A total of 92.7% women consumed 80% to 100% of supplements as instructed; the mean number of supplements consumed was 177 capsules (Table 2). No serious adverse effects were reported. The adverse effects were nausea, vomiting, or other mild gastrointestinal discomfort: 133 women in the folic acid group (2.2%) reported gastrointestinal discomfort, 212 (3.6%) in the iron–folic acid group, and 355 (6.0%) in the MMN group (P < .001).
Quiz Ref IDThe perinatal mortality rate was 8.76 of 1000 births for the folic acid group, 8.73 of 1000 for the iron–folic acid group, and 8.25 of 1000 for the MMN group. Compared with prenatal folic acid alone, neither iron–folic acid (RR, 1.00; 95% CI, 0.68-1.46; P = .99) nor MMN supplements (RR, 0.94; 95% CI, 0.64-1.39; P = .76) affected the risk of perinatal mortality (Table 3). Compared with iron–folic acid, MMN did not affect the risk of perinatal mortality (RR, 0.94; 95% CI, 0.64-1.39; P = .77). Similarly, risk of stillbirths, early neonatal deaths, neonatal deaths, or infant deaths did not differ by supplement group.
Compared with folic acid alone, iron–folic acid and MMN increased third-trimester maternal Hb concentration by 0.04 and 0.06 g/dL, respectively, and decreased the anemia prevalence by 28% and 29% (Table 4), respectively, with a number needed to treat of 47 (95% CI, 33-81) for the iron–folic acid group and 46 (95% CI, 32-77) for the MMN group. Quiz Ref IDNeither gestation duration nor birth weight or length differed significantly by supplement group.
In this primarily nonanemic rural population, prenatal supplementation with iron–folic acid or MMN vs folic acid alone did not decrease the risk of perinatal mortality or other infant or maternal outcomes except maternal anemia. Quiz Ref IDCompared with folic acid alone, iron–folic acid and MMN increased Hb concentration and reduced anemia by about 30%. Our study population was rural (91% were farmers); nearly all women had at least a secondary education, and few were undernourished or anemic. In addition, having monitored their menstrual cycle for 2 or more months before enrollment, women were cognizant of their last menstrual period and prenatal health. Once enrolled, women were followed monthly and delivered in the hospital. The lack of differences in infant outcomes with prenatal supplementation may underline the importance of secondary factors, such as nutritional status, prenatal care, and economic status in assessing the degree to which our findings can be generalized.
Our findings are consistent with 2 previous meta-analyses of RCTs in developing countries comparing the effects of iron–folic acid with MMN on neonatal and perinatal mortality.34,35 Unlike one meta-analysis36 that found a trend toward higher early neonatal mortality in the group receiving MMN vs iron–folic acid alone, we found no difference between these groups. A recent meta-analysis34 showed an increased risk of neonatal mortality with MMN compared with iron–folic acid in settings where less than 60% of births occurred in facilities; however, consistent with our trial, there was no increased risk in settings where most births occurred in facilities. Thus, our results should be interpreted in the context of the existing burden of micronutrient deficiencies, adverse pregnancy, and fetal outcomes, and the setting. Our study population had low prevalence rates of all the outcomes assessed in the study, including a low prevalence of anemia (5%-7%) in late pregnancy and a low birth weight prevalence (approximately 2%), which were even lower than those seen in many industrialized countries. At such low rates of adverse outcomes, it is not surprising that the intervention had no impact. As such, this trial is not comparable with many of the studies included in the meta-analyses. Unlike many trials conducted in poor populations in developing countries, our trial is generalizable to a well-nourished population of nonanemic or mildly anemic women with good access to health care.
In this primarily nonanemic population, the relative reduction of anemia (approximately 30%) was substantial. Although iron status was not assessed in the entire population, this reduction suggests about 30% of anemia was due to iron deficiency, and only one-third of anemic women in our population could be expected to respond to iron supplementation. Anemic women are likely to be iron deficient and would benefit from supplements containing iron. However, overall improvement in Hb concentration was limited, owing to low anemia prevalence at baseline (<6%). Because 21.7% of the population had high Hb levels (≥13.2 g/dL)37,38 at enrollment and high Hb level has been hypothesized as a risk factor, we conducted post hoc analyses to test for possible interaction between supplement groups and maternal baseline Hb status (<13.2 g/dL vs ≥13.2 g/dL) on perinatal mortality by using Breslow-Day tests. All P values for interaction tests were not significant (P > .90).
Although we did not find a significant difference in low birth weight with prenatal MMN vs iron–folic acid supplementation, the point estimate (10% reduction) was similar to that estimated (11%-14%) in the previous meta-analyses.13,35 In our study population, we excluded women with moderate anemia at enrollment, and the low birth weight incidence was smaller than that observed in previous studies, diminishing the possibility of observing a significant effect. Our findings with regard to the effect of iron differ with those of 2 trials conducted in the United States. One trial compared the effects of iron alone vs placebo and the other compared prenatal vitamins with and without iron, both in iron-replete, nonanemic pregnant women.39,40 In both US trials, the iron-supplemented group had a significantly higher mean birth weight compared with the control group; the trial comparing iron with placebo showed a significantly lower incidence of infants with low birth weight39 and increased gestational age at delivery. Although it is difficult to compare these trials owing to differences in the populations and control supplements, the low birth weight incidence among the control groups in the US studies (9.5%-16.7%) was much higher than our study (approximately 2%).
The inconsistent results between our study and those of other studies may relate to the modifying effects of maternal socioeconomic and nutritional status in response to micronutrient supplementation. In an RCT in rural western China,41 effects of micronutrient supplementation were observed in the poorest one-third of households but not in wealthier households. Compared with folic acid alone, women from the poorest households who received iron–folic acid had significant reductions in both preterm birth and early neonatal mortality; women who received MMN had a significant reduction in preterm births and low birth weight. In the large-scale SUMMIT trial in Indonesia,22 effects on early infant mortality (0-90 days) were observed among undernourished or anemic women; compared with women receiving iron–folic acid, women who received MMN showed significant reductions in early infant mortality (25% in undernourished women and 38% in anemic women, respectively).
Quiz Ref IDAside from the lack of a placebo group and information on the micronutrient status, the major limitation of the study was that the actual power was not adequate to detect a difference in perinatal mortality by supplement group, primarily because the observed perinatal mortality rate dramatically decreased during the past decade with the rapid socioeconomic development in China. Although there were no evident differences in perinatal mortality, we cannot rule out small differences because of inadequate sample size. Our study has several strengths. Supplements were randomized by individual. Capsule-taking was confirmed by independent household visits, and the compliance was greater than 90%. All pregnancy outcomes, including stillbirths, abortions, and early neonatal deaths, were ascertained by active community surveillance, review of vital registration certificates, and review of hospital records. Assessment of birth weight was conducted using standardized and accurate equipment and trained staff. Finally, less than 1% of those enrolled were lost to follow-up.
In summary, our study is, to our knowledge, the first large-scale, double-blind, individual RCT to directly assess the impact of prenatal supplementation on perinatal mortality in a well-nourished Chinese population with good access to health care. Given perinatal and infant mortality were similar across supplement groups, the slight improvement in Hb status with iron–folic acid and MMN supplements among nonanemic or mildly anemic women provides some limited additional support for prophylactic iron supplementation to prevent third-trimester maternal anemia.
Correspondence: Jian-meng Liu, PhD, Institute of Reproductive and Child Health, Peking University Health Science Center, Department of Epidemiology, 38 College Rd, Haidian District, Beijing 100191, China (firstname.lastname@example.org).
Accepted for Publication: September 8, 2012.
Published Online: January 7, 2013. doi:10.1001/jamainternmed.2013.1632
Author Contributions: Dr Liu had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis. Study concept and design: Liu, Mei, and Cogswell. Acquisition of data: Liu, Mei, and Ren. Analysis and interpretation of data: Liu, Mei, Ye, Serdula, Ren, and Cogswell. Drafting of the manuscript: Liu, Mei, Serdula, and Cogswell. Critical revision of the manuscript for important intellectual content: Liu, Mei, Ye, Serdula, Ren, and Cogswell. Statistical analysis: Liu and Mei. Obtained funding: Liu, Mei, and Cogswell. Administrative, technical, and material support: Liu, Mei, Ye, Serdula, Ren, and Cogswell. Study supervision: Liu, Mei, Ren, and Cogswell.
Conflict of Interest Disclosures: None reported.
Funding/Support: The study is supported by a cooperative agreement between Peking University Health Science Center and the Centers for Disease Control and Prevention.
Role of the Sponsor: The findings and conclusions in this report are those of the authors and do not necessarily represent the official position of Centers for Disease Control and Prevention. The sponsor had a role in study design, data collection, data analysis and interpretation, and writing of the report.
Additional Contributions: We are grateful to all study participants and the hundreds of health care workers from Yuanshi, Mancheng, Xianghe, Fengrun, and Laoting counties in China who made the project possible. We thank Wei-cheng You, MD, Michael A. Brown, MPH, Ibrahim Parvanta, MS, Robert J. Berry, MD, and Jacqueline Gindler, MD, and the members of the data safety and monitoring board (Michael J. Dibley [chair], MPH, Sean Lynch, PhD, Christine McClaren, PhD, Shuigao Jin, PhD, and Zhenglai Wu, MD) for their support of this project. We also thank Zhiwen Li, PhD, Hongtian Li, MD, Lei Jin, PhD, Le Zhang, PhD, Linlin Wang, PhD, Quangang Qu, PhD,Yali Zhang, PhD, Juan Wang, MD, Weixian Gao, BS, Zheng Yao, MD, and all other staff who have currently or previously worked on the project at the Peking University Institute of Reproductive and Child Health.