Iron Deficiency and Iron Deficiency Anemia During Pregnancy: Screening and Supplementation

The U.S. Preventive Services Task Force (USPSTF) makes recommendations about the effectiveness of specific preventive care services for patients without obvious related signs or symptoms to improve the health of people nationwide. 

It bases its recommendations on the evidence of both the benefits and harms of the service and an assessment of the balance. The USPSTF does not consider the costs of providing a service in this assessment. 

The USPSTF recognizes that clinical decisions involve more considerations than evidence alone. Clinicians should understand the evidence but individualize decision making to the specific patient or situation. Similarly, the USPSTF notes that policy and coverage decisions involve considerations in addition to the evidence of clinical benefits and harms. 

The USPSTF is committed to mitigating the health inequities that prevent many people from fully benefiting from preventive services. Systemic or structural racism results in policies and practices, including health care delivery, that can lead to inequities in health. The USPSTF recognizes that race, ethnicity, and gender are all social rather than biological constructs. However, they are also often important predictors of health risk. The USPSTF is committed to helping reverse the negative impacts of systemic and structural racism, gender-based discrimination, bias, and other sources of health inequities, and their effects on health, throughout its work.

The aim of routine screening or iron supplementation for treatment of iron deficiency and iron deficiency anemia during pregnancy is to improve maternal and infant health outcomes. Iron deficiency is the leading cause of anemia during pregnancy.¹ According to National Health and Nutrition Examination Survey (NHANES) data from 1999 to 2006, overall estimated prevalence of iron deficiency during pregnancy is near 18% and increases across the three trimesters of pregnancy (from 6.9% to 14.3% to 28.4%).² An estimated 5% of pregnant persons are anemic.^1,2 In the United States, there are disparities in prevalence of iron deficiency anemia by race, ethnicity, and social factors (e.g., socioeconomic status, nutritional status, and food insecurity).^1,2

Due to lack of available data, the USPSTF concludes that the current evidence is insufficient, and the balance of benefits and harms of screening for iron deficiency and iron deficiency anemia in asymptomatic pregnant persons on maternal and infant health outcomes cannot be determined (I statement).

Due to lack of available data, the USPSTF concludes that the current evidence is insufficient, and the balance of benefits and harms of iron supplementation in asymptomatic pregnant persons on maternal and infant health outcomes cannot be determined (I statement).

See Table 1 for more information on the USPSTF recommendation rationale and assessment. For more details on the methods the USPSTF uses to determine the net benefit, see the USPSTF Procedure Manual.³

Patient Population Under Consideration

This recommendation applies to asymptomatic pregnant adolescents and adults. This recommendation does not apply to pregnant persons who are malnourished, have symptoms of iron deficiency or iron deficiency anemia, or have specific hematologic conditions or nutritional deficiencies that may increase their need for iron.

Definitions

Iron is necessary for production of hemoglobin, an essential protein in blood required to transport oxygen throughout the body. Iron is also necessary for the production of additional proteins that are vital to various metabolic pathways.⁴ Iron deficiency refers to depletion of iron stores.¹ Depletion of iron may progress to iron deficiency anemia.¹ Increased demands for iron during pregnancy enhances vulnerability for iron deficiency and iron deficiency anemia.¹ Screening for iron deficiency and iron deficiency anemia often includes measurement of hematologic indices (e.g., hemoglobin, hematocrit, and ferritin values), and an abnormal screening test result may be followed by treatment with iron therapy.¹ Supplementation refers to routine provision of supplemental iron, without specifically measuring hematologic indices.

Suggestions for Practice Regarding the I Statements

In deciding whether to routinely screen or supplement for iron deficiency with or without anemia during pregnancy, clinicians caring for pregnant persons should consider the following.

Potential Preventable Burden

Due to inconsistent surveillance systems to assess iron deficiency and iron deficiency anemia in the United States, overall prevalence data are limited; however, prevalence increases over the course of pregnancy.^2,5 Based on recent survey data, Black and Mexican American pregnant persons are disproportionately affected by iron deficiency anemia in pregnancy, with social determinants of health as possible contributors to these disparities.^1,2 However, factors such as nutritional status, food insecurity, or access to healthcare were not considered.^1,2

The USPSTF found limited evidence on current methods, including questionnaires and risk prediction tools, to identify pregnant persons at increased risk for iron deficiency with or without anemia. Commonly cited risk factors include a diet low in iron-rich foods (e.g., vegan diet with inadequate sources of iron), gastrointestinal conditions or medications that can decrease iron absorption (e.g., antacids), or a short interval between pregnancies.¹ Tobacco use and living at a high altitude may impact hematologic indices due to increases in hematocrit and hemoglobin values.¹ The evidence review identified three studies reporting strategies to predict iron deficiency or iron deficiency anemia during pregnancy.¹ Generally, across the three studies,^6-8 an evaluation of the tool’s utility to predict true iron deficiency or iron deficiency anemia during pregnancy was limited.¹

Potential Harms

Potential screening approaches to identify asymptomatic pregnant persons with iron deficiency or iron deficiency anemia are unlikely to cause serious harms, but evidence is limited. Common adverse effects of iron supplementation or treatment include gastrointestinal tract symptoms such as nausea, constipation, abdominal pain, and vomiting.¹

Current Practice

The USPSTF found limited evidence on current practices of screening and supplementation to prevent adverse maternal or infant health outcomes from iron deficiency or iron deficiency anemia. Clinical practice guidelines on screening and supplementation vary (see the “Recommendations of Others” section for additional information).^1,9 However, screening and supplementation are likely common. For screening, a surveillance report among Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) participants reported that more than half of enrolled pregnant persons (53%) underwent hemoglobin testing during their first trimester in 2018.^1,10 There may be other reasons that clinicians measure hematologic indices, such as to prepare for cesarean delivery or anticipated blood loss during delivery. Additionally, disparities in screening may exist. In a U.S. study¹¹ (n=268,594) of Medicaid recipients across four states, Black, Hispanic, and Asian/Pacific Islander participants were less likely (odds ratio [OR], 0.51 to 0.92) to receive a complete blood count in three of four states surveyed compared with White participants.¹ For supplementation, according to NHANES data from 1996 to 2006, many pregnant persons (77%) reported using a supplement, often containing iron, within the previous 30 days.^1,12 Use of iron supplements may differ by race, geography, and social factors.¹ For example, in a study using NHANES survey data from 1999 to 2010, pregnant persons who were food insecure had lower mean iron intake from supplements compared with pregnant persons who were food secure.^1,13 Pregnant persons may be screened (e.g., with measurement hematologic indices in the first trimester) or supplemented (e.g., with prenatal vitamins) concurrently. 

Additional Tools and Resources

The National Institutes of Health’s Office of Dietary Supplements provides a fact sheet on iron for consumers in English (https://ods.od.nih.gov/factsheets/Iron-Consumer) and Spanish (https://ods.od.nih.gov/factsheets/Iron-DatosEnEspanol) and for clinicians (https://ods.od.nih.gov/factsheets/Iron-HealthProfessional).

The U.S. Department of Health and Human Services’ Office on Women’s Health provides a fact sheet about iron deficiency anemia for patients (https://www.womenshealth.gov/a-z-topics/iron-deficiency-anemia).

Other Related USPSTF Recommendations

The USPSTF has issued separate recommendations on screening for iron deficiency anemia in children ages 6 to 24 months¹⁴ and folic acid supplementation to prevent neural tube defects in persons who plan to or could become pregnant.¹⁵

This recommendation is consistent with the 2015 recommendation statement on screening and supplementation for iron deficiency anemia in pregnancy. In 2015, the USPSTF concluded that the current evidence was insufficient to assess the balance of benefits and harms of screening for iron deficiency anemia in pregnant women to prevent adverse maternal health and birth outcomes (I statement).¹⁶ The USPSTF also concluded that the current evidence was insufficient to assess the balance of benefits and harms of routine iron supplementation for iron deficiency anemia in pregnant women to prevent adverse maternal health and birth outcomes (I statement).¹⁶

Scope of Review

The USPSTF commissioned a systematic review¹ to update its 2015 recommendation on screening and supplementation for iron deficiency anemia during pregnancy. In this current recommendation, the USPSTF broadened its review to include iron deficiency without anemia; it reviewed evidence on the benefits and harms of screening and supplementation for iron deficiency with and without anemia on maternal and infant health outcomes in asymptomatic pregnant persons. To assist with efforts to generalize the evidence to an asymptomatic U.S. pregnant population, the USPSTF considered studies conducted in settings similar to the United States (i.e., categorized as “high” or “very high” on the United Nations Human Development Index). In addition, to address critical gaps in the evidence identified in 2015,¹⁷ the USPSTF sought evidence on the association between change in maternal iron status and improvement in infant and maternal outcomes in pregnant persons with iron deficiency with or without anemia. 

Benefits of Screening (Early Detection) and Treatment

The review found no evidence on the benefits of screening and treatment for screen-detected iron deficiency and iron deficiency anemia during pregnancy on maternal and infant health outcomes.¹ A single observational study addressed the association between change in maternal iron status in pregnant persons with iron deficiency with or without anemia and clinical outcomes. ¹ In the study (n=20,690)¹⁸ in pregnant persons responding to treatment (defined as persons with a normal hemoglobin value at delivery who reported taking iron supplementation), therapy was associated with reduction in the odds of preeclampsia (adjusted OR [aOR], 0.75 [95% CI, 0.61 to 0.91]) and preterm birth (aOR, 0.59 [95% CI, 0.47 to 0.72]) compared with nonanemic persons.^1,18 Nonresponse to therapy or untreated anemia was also associated with increased risk of preterm birth and preeclampsia (aOR, 1.44 [95% CI, 1.16 to 1.76] and 1.45 [95% CI, 1.26 to 1.67], respectively) compared with no anemia.^1,18 Comparison on these outcomes between pregnant persons taking iron therapy (whether or not successfully treated) with persons not taking iron therapy was not reported, limiting assessment of the association between iron therapy and improvement in health outcomes.¹ Additional limitations to generalizing the study’s findings included the definition of anemia (based on reported iron intake) and unclear or unreported iron dose, timing, and therapy duration.¹

Benefits of Supplementation 

Maternal Health Outcomes

The review identified 16 studies comparing the effects of routine iron supplementation with no supplementation during pregnancy.¹ Timing of starting supplementation varied across studies, from the first prenatal visit to 20 weeks’ gestation, and continued to delivery.¹ Across the 16 studies, evidence on the effects of iron supplementation during pregnancy on maternal or infant health outcomes was limited, inconsistent, or without clear benefit.¹ One trial (n=430) reported no differences in maternal quality of life (across eight health concepts) with iron supplementation compared with placebo.^1,19 Five trials^20-24 (N=13,610) found no statistically significant differences on rates of hypertensive disorders of pregnancy with iron supplementation compared with placebo or no iron (4.7% vs. 3.1% [pooled, weighted rates]; relative risk [RR], 1.24 [95% CI, 0.75 to 2.06]; I²=48.0%).¹ Based on a pooled analysis, eight trials^19,20,23-28 (N=4,919) found no statistically significant differences in rates of cesarean delivery (42.8% vs. 41.5%; RR, 1.01 [95% CI, 0.90 to 1.14]; I²=42.7%).¹ Generally, studies of cesarean delivery did not report procedure indications, which could reflect practice variability, limiting interpretation of this evidence.¹ In four trials reporting maternal gestational diabetes and maternal hemorrhage, results were imprecise and uncertain.¹ Two trials^23,25 (N=2,214) found no differences in rates of maternal gestational diabetes in pregnant persons receiving iron supplementation vs. placebo and two trials^20,28 (N=341) found no statistically significant differences in rates of maternal hemorrhage; however, these rates were low.¹

Infant Health Outcomes

Across six supplementation trials^{19,20,22,24,26,29} reporting infant health outcomes, evidence was limited or demonstrated no benefit.¹ Five trials reported no association between supplementation and infant mortality. In post-hoc analysis, one trial reported a statistically significant difference in rates of neonatal deaths in the supplementation group compared with the control group (1.1% vs. 2.0%; RR, 0.53 [95% CI, 0.29 to 0.97]).¹ Five trials^{21,23,25,29,30} (N=16,827) of maternal iron supplementation reported no statistically significant differences in risk of preterm birth (5 trials; 5.5% vs. 6.0%; RR, 0.92 [95% CI, 0.81 to 1.04]; I²=0.0%).¹ Pooled analysis of six trials^{19-21,26,29,30} (N=15,591) of maternal iron supplementation reported no statistically significant differences in infants with low birth weight (6 trials; 2.7% vs. 2.9%; RR, 0.95 [95% CI, 0.79 to 1.14]; I²=0.0%).¹  Across four trials^23-25,29 (N=5,386) reporting infants small for gestational age, evidence was inconsistent and imprecise, with most studies reporting no differences (4 trials; 15.3% vs. 15.2%; RR, 0.94 [95% CI, 0.67 to 1.31]; I²=75.5%).¹ A pooled analysis reported few differences between supplementation compared with placebo.¹ Low birth weight was defined as less than 2,500 g and small for gestational age or intrauterine growth restriction was defined as birth weight less than 10th percentile for gestational age.¹ 

Maternal Hematologic Outcomes

While the USPSTF found inconsistent evidence on maternal iron supplementation during pregnancy to improve maternal and infant health outcomes, across 16 trials^19-41 there was evidence of an association between supplementation and improved maternal hematologic indices (e.g., hemoglobin and ferritin values) and decreased risk of maternal iron deficiency anemia, iron deficiency, and anemia compared with placebo or no therapy.¹ Seven trials^{19,21,26,27,31,37,40} (N=4,045) reported on maternal iron deficiency anemia with supplementation; iron supplementation was associated with decreased risk of maternal iron deficiency anemia during the third trimester (3 trials; N=330; 9.1% vs. 13.8%; RR, 0.63 [95% CI, 0.41 to 0.97]; I²=0%; absolute risk difference [ARD], -4% [95% CI, -8% to 0%]) and at term (4 trials; N=2,230; 8.6% vs. 19.8%; RR, 0.40 [95% CI, 0.26 to 0.61]; I²=20.5%; ARD, -10% [95% CI, -16% to -3%]).¹ Nine trials^{19,21,27,30-32,35,38,40} (N=16,556) reported on maternal iron deficiency with supplementation; iron supplementation was associated with decreased risk of maternal iron deficiency during the third trimester (4 trials; N=1,220; 40.3% vs. 57.1%; RR, 0.70 [95% CI, 0.53 to 0.92]; I²=77.4%; ARD, -17% [95% CI, -24% to -10%]) and at term (6 trials; N=2,361; 46% vs. 70%; RR, 0.47 [95% CI, 0.33 to 0.67]; I²=81.9%; ARD, -34% [95% CI, -46% to -22%]).¹ Nine trials^{19,27,29-32,35,38,40} (N=20,330) reported on maternal anemia; iron supplementation was associated with decreased risk of maternal anemia during the third trimester (7 studies; N=2,148; 18.1% vs. 26.0%; RR, 0.71 [95% CI, 0.51 to 0.97]; I²=64.2%; ARD, -7.97% [95% CI, -15.28% to -0.66%]) and at term (4 trials; N=2,261; 10.9% vs. 22.5%; RR, 0.43 [95% CI, 0.26 to 0.72]; I²=43.7%; ARD, -11.73% [95% CI, -14.87% to -8.60%]).¹ Fifteen trials^{20,21,23-29,31,38,40} (N=20,069) reported maternal hemoglobin values and 13 trials^{19-21,23,25-28,30,31,38,40} (N=19,075) reported maternal ferritin values compared with placebo; most studies found higher hemoglobin and serum ferritin values at term compared with placebo, with inconsistent findings at other time points.¹

Infant Hematologic Outcomes

Evidence of intermediate outcomes in infants was limited to two trials^19,30 (N=12,943) reporting no differences in infant hematologic indices at 6 months or 1 year.¹

Maternal and Infant Hematologic Outcomes

Evidence on the association between maternal supplementation and change in maternal iron status on improvement in infant and maternal outcomes was limited to the same single study (n=20,690)¹⁸ of pregnant persons discussed in the screening section. 

Harms of Screening and Supplementation

No trials reported on harms of screening. Twelve trials^{19,23,25-27,29-32,38,40,42} (N=22,716) reported evidence on the harms of routine supplementation during pregnancy.¹ Most trials reported transient gastrointestinal effects such as nausea, constipation, and diarrhea, with five trials reporting no difference in transient gastrointestinal effects in comparison groups.^{1,19,26,27,29,42} A single trial (n=12,513) reported that iron supplementation starting in the second trimester was associated with increased risk of gastrointestinal symptoms vs. placebo (3.6% vs. 2.3%; RR, 1.59 [95% CI, 1.28 to 1.97]).^1,30 Using medication adherence as a proxy for harms, nine studies reported no statistically significant differences in adherence to supplementation between comparison groups.¹ In a separate trial, adherence to iron therapy was higher in adults taking iron supplementation compared with placebo and not statistically significant in adolescents (n=111; 2.2% vs 16.1%; p=0.036 and 4.5% vs 12.6%; p=0.320, respectively).^1,26 Infant harms were not reported in any studies.¹

See Table 2 for research needs and gaps related to screening and supplementation for iron deficiency and iron deficiency anemia during pregnancy.

The American College of Obstetricians and Gynecologists, American Academy of Family Physicians, and Centers for Disease Control and Prevention recommend that all pregnant persons be screened for anemia at their first prenatal visit, preferably during the first trimester of pregnancy.^43-45

The Centers for Disease Control and Prevention recommends universal supplementation of all pregnant persons with an oral low-dose iron supplement (30 mg/day).⁴⁵ The American College of Obstetricians and Gynecologists recommends evaluation for pregnant women who meet criteria for anemia to determine the cause, followed by treatment with supplemental iron for those with iron deficiency anemia along with prenatal vitamins.⁴³ The U.S. Department of Agriculture and U.S. Department of Health and Human Services’ “Dietary Guidelines for Americans, 2020–2025” recommends that pregnant women or women planning to become pregnant take a supplement with iron when recommended by a clinician.⁴⁶ In addition, women following a vegetarian or vegan dietary pattern should discuss with a clinician whether supplementation of iron, vitamin B₁₂, other nutrients, or some combination thereof is needed.⁴⁶

1. Cantor A, Holmes R, Bougatsos C, Atchison C, DeLoughery T, Chou R. Screening and Supplementation for Iron Deficiency and Iron Deficiency Anemia in Pregnancy: A Systematic Review for the U.S. Preventive Services Task Force. Evidence Synthesis No. 239. AHRQ Publication No. 24-05313-EF-1. Rockville, MD: Agency for Healthcare Research and Quality; 2023.
2. Mei Z, Cogswell ME, Looker AC, et al. Assessment of iron status in US pregnant women from the National Health and Nutrition Examination Survey (NHANES), 1999–2006. Am J Clin Nutr. 2011;93(6):1312-1320.
3. U.S. Preventive Services Task Force. Procedure Manual. Accessed January 24, 2024. https://uspreventiveservicestaskforce.org/uspstf/about-uspstf/methods-and-processes/procedure-manual
4. Griffin IJ, Abrams SA. Iron and breastfeeding. Pediatr Clin North Am. 2001;48(2):401-413.
5. Scholl TO. Iron status during pregnancy: setting the stage for mother and infant. Am J Clin Nutr. 2005;81(5):1218s-1222s.
6. Kirschner W, Dudenhausen JW, Henrich W. Are there anamnestic risk factors for iron deficiency in pregnancy? Results from a feasibility study. J Perinat Med. 2016;44(3):309-314.
7. Yefet E, Yossef A, Nachum Z. Prediction of anemia at delivery. Sci Rep. 2021;11(1):6309.
8. Casanova BF, Sammel MD, Macones GA. Development of a clinical prediction rule for iron deficiency anemia in pregnancy. Am J Obstet Gynecol. 2005;193(2):460-466.
9. Jefferds ME, Mei Z, Addo Y, et al. Iron deficiency in the United States: limitations in guidelines, data, and monitoring of disparities. Am J Public Health. 2022;112(S8):S826-S835.
10. Kanu FA, Hamner HC, Scanlon KS, Sharma AJ. Anemia among pregnant women participating in the Special Supplemental Nutrition Program for Women, Infants, and Children—United States, 2008–2018. MMWR Morb Mortal Wkly Rep. 2022;71:813-819.
11. Gavin NI, Adams EK, Hartmann KE, Benedict MB, Chireau M. Racial and ethnic disparities in the use of pregnancy-related health care among Medicaid pregnant women. Matern Child Health J. 2004;8(3):113-126.
12. Branum AM, Bailey R, Singer BJ. Dietary supplement use and folate status during pregnancy in the United States. J Nutr. 2013;143(4):486-492.
13. Park CY, Eicher-Miller HA. Iron deficiency is associated with food insecurity in pregnant females in the United States: National Health and Nutrition Examination Survey 1999-2010. J Acad Nutr Diet. 2014;114(12):1967-1973.
14. U.S. Preventive Services Task Force. Screening for iron deficiency anemia in young children: U.S. Preventive Services Task Force recommendation statement. Pediatrics. 2015;136(4):746-752.
15. US Preventive Services Task Force. Folic acid supplementation to prevent neural tube defects: US Preventive Services Task Force reaffirmation recommendation statement. JAMA. 2023;330(5):454-459.
16. U.S. Preventive Services Task Force. Screening for iron deficiency anemia and iron supplementation in pregnant women to improve maternal health and birth outcomes: U.S. Preventive Services Task Force recommendation statement. Ann Intern Med. 2015;163(7):529-536.
17. Kemper AR, Fan T, Grossman DC, Phipps MG. Gaps in evidence regarding iron deficiency anemia in pregnant women and young children: summary of US Preventive Services Task Force recommendations. Am J Clin Nutr. 2017;106(Suppl 6):1555s-1558s.
18. Detlefs SE, Jochum MD, Salmanian B, McKinney JR, Aagaard KM. The impact of response to iron therapy on maternal and neonatal outcomes among pregnant women with anemia. Am J Obstet Gynecol MFM. 2022;4(2):100569.
19. Makrides M, Crowther CA, Gibson RA, Gibson RS, Skeaff CM. Efficacy and tolerability of low-dose iron supplements during pregnancy: a randomized controlled trial. Am J Clin Nutr. 2003;78(1):145-153.
20. Barton DP, Joy MT, Lappin TR, et al. Maternal erythropoietin in singleton pregnancies: a randomized trial on the effect of oral hematinic supplementation. Am J Obstet Gynecol. 1994;170(3):896-901.
21. Falahi E, Akbari S, Ebrahimzade F, Gargari BP. Impact of prophylactic iron supplementation in healthy pregnant women on maternal iron status and birth outcome. Food Nutr Bull. 2011;32(3):213-217.
22. Li Z, Mei Z, Zhang L, et al. Effects of prenatal micronutrient supplementation on spontaneous preterm birth: a double-blind randomized controlled trial in China. Am J Epidemiol. 2017;186(3):318-325.
23. Ouladsahebmadarek E, Sayyah-Melli M, Taghavi S, Abbasalizadeh S, Seyedhejazie M. The effect of supplemental iron elimination on pregnancy outcome. Pakistan J Med Sci. 2011;27(3):641-645.
24. Ziaei S, Norrozi M, Faghihzadeh S, Jafarbegloo E. A randomised placebo-controlled trial to determine the effect of iron supplementation on pregnancy outcome in pregnant women with haemoglobin 13.2 g/dl. BJOG. 2007;114(6):684-688.
25. Chan KK, Chan BC, Lam KF, Tam S, Lao TT. Iron supplement in pregnancy and development of gestational diabetes—a randomised placebo-controlled trial. BJOG. 2009;116(6):789-798.
26. Meier PR, Nickerson HJ, Olson KA, Berg RL, Meyer JA. Prevention of iron deficiency anemia in adolescent and adult pregnancies. Clin Med Res. 2003;1(1):29-36.
27. Zhao G, Xu G, Zhou M, et al. Prenatal iron supplementation reduces maternal anemia, iron deficiency, and iron deficiency anemia in a randomized clinical trial in rural China, but iron deficiency remains widespread in mothers and neonates. J Nutr. 2015;145(8):1916-1923.
28. Ziaei S, Mehrnia M, Faghihzadeh S. Iron status markers in nonanemic pregnant women with and without iron supplementation. Int J Gynaecol Obstet. 2008;100(2):130-132.
29. Zeng L, Dibley MJ, Cheng Y, et al. Impact of micronutrient supplementation during pregnancy on birth weight, duration of gestation, and perinatal mortality in rural western China: double blind cluster randomised controlled trial. BMJ. 2008;337:a2001.
30. Liu JM, 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.
31. Cogswell ME, Parvanta I, Ickes L, Yip R, Brittenham GM. Iron supplementation during pregnancy, anemia, and birth weight: a randomized controlled trial. Am J Clin Nutr. 2003;78(4):773-781.
32. Eskeland B, Malterud K, Ulvik RJ, Hunskaar S. Iron supplementation in pregnancy: is less enough? A randomized, placebo controlled trial of low dose iron supplementation with and without heme iron. Acta Obstet Gynecol Scand. 1997;76(9):822-828.
33. Chen S, Li N, Mei Z, et al. Micronutrient supplementation during pregnancy and the risk of pregnancy-induced hypertension: a randomized clinical trial. Clin Nutr. 2019;38(1):146-151.
34. Liu Y, Li N, Mei Z, et al. Effects of prenatal micronutrients supplementation timing on pregnancy-induced hypertension: secondary analysis of a double-blind randomized controlled trial. Matern Child Nutr. 2021;17(3):e13157.
35. Milman N, Agger AO, Nielsen OJ. Iron supplementation during pregnancy. Effect on iron status markers, serum erythropoietin and human placental lactogen. A placebo controlled study in 207 Danish women. Dan Med Bull. 1991;38(6):471-476.
36. Milman N, Byg KE, Agger AO. Hemoglobin and erythrocyte indices during normal pregnancy and postpartum in 206 women with and without iron supplementation. Acta Obstet Gynecol Scand. 2000;79(2):89-98.
37. Milman N, Agger AO, Nielsen OJ. Iron status markers and serum erythropoietin in 120 mothers and newborn infants. Effect of iron supplementation in normal pregnancy. Acta Obstet Gynecol Scand. 1994;73(3):200-204.
38. Romslo I, Haram K, Sagen N, Augensen K. Iron requirement in normal pregnancy as assessed by serum ferritin, serum transferrin saturation and erythrocyte protoporphyrin determinations. Br J Obstet Gynaecol. 1983;90(2):101-107.
39. Serdula MK, Zhou Y, Li H, Liu JM, Mei Z. Prenatal iron containing supplements provided to Chinese women with no or mild anemia had no effect on hemoglobin concentration in post-partum women or their infants at 6 and 12 months of age. Eur J Clin Nutr. 2019;73(11):1473-1479.
40. Siega-Riz AM, Hartzema AG, Turnbull C, Thorp J, McDonald T, Cogswell ME. The effects of prophylactic iron given in prenatal supplements on iron status and birth outcomes: a randomized controlled trial. Am J Obstet Gynecol. 2006;194(2):512-519.
41. Wang L, Mei Z, Li H, Zhang Y, Liu J, Serdula MK. Modifying effects of maternal Hb concentration on infant birth weight in women receiving prenatal iron-containing supplements: a randomised controlled trial. Br J Nutr. 2016;115(4):644-649.
42. Jafarbegloo E, Ahmari Tehran H, Dadkhah Tehrani T. Gastrointestinal complications of ferrous sulfate in pregnant women: a randomized double-blind placebo-controlled trial. Iran Red Crescent Med J. 2015;17(8):e15001.
43. Anemia in pregnancy: ACOG Practice Bulletin, Number 233. Obstet Gynecol. 2021;138(2):e55-e64.
44. Killip S, Bennett JM, Chambers MD. Iron deficiency anemia. Am Fam Physician. 2007;75(5):671-678.
45. Yip R, Parvanta I, Cogswell ME, et al. Recommendations to prevent and control iron deficiency in the United States. MMWR Morb Mortal Wkly Rep. 1998;47(RR3):1-29.
46. U.S. Department of Agriculture and U.S. Department of Health and Human Services. Dietary Guidelines for Americans, 2020-2025. Accessed January 24, 2024. https://www.dietaryguidelines.gov/

To fulfill its mission to improve health by making evidence-based recommendations for preventive services, the USPSTF routinely highlights the most critical evidence gaps for making actionable preventive services recommendations. For each evidence gap below, research should focus on settings similar to those in the United States to assist in generalizability to a U.S. primary care population. This table summarizes the key bodies of evidence needed for the USPSTF to make a recommendation for screening and supplementation for iron deficiency and iron deficiency anemia during pregnancy.