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Postpartum iron status in nonlactating participants and
nonparticipants in the Special Supplemental Nutrition
1–4
Program for Women, Infants, and Children
Pamela R Pehrsson, Phylis B Moser-Veillon, Laura S Sims, Carol W Suitor, and Estelle Russek-Cohen Downloaded from https://academic.oup.com/ajcn/article/73/1/86/4729705 by guest on 06 January 2023
ABSTRACT bears. Although many women are in a nutritionally depleted state
Background: Iron deficiency, a pervasive problem among low- before and after pregnancy (1), maternal and child health services
income women of childbearing age, threatens maternal health in our society focus specifically on fetal health (2). This is a seri-
and pregnancy outcomes. The Special Supplemental Nutrition ous problem among many lower-income women, who are espe-
Program for Women, Infants, and Children (WIC) was designed cially prone to health problems such as nutritional deficiencies and
to alleviate health problems and provides supplemental nutri- obesity. The Special Supplemental Nutrition Program for Women,
tious foods, nutrition education, and health care referrals. Infants, and Children (WIC), a federally funded program, was
Objectives: The aim of this study was to examine the benefits instituted to alleviate some of the most prevalent nutritional prob-
associated with participation in WIC in terms of biochemical lems. WIC serves 7 million people, primarily pregnant women
tests of postpartum iron status in nonlactating women. and infants, through distribution of nutritious supplemental food,
Design: WIC participants (n = 57) and eligible nonparticipants nutrition education, and assistance with health care referrals.
(n = 53), matched by race and age, were followed bimonthly over A priority system was developed to identify the most critical
6 mo postpartum. Finger stick blood samples (500 L) were col- applicants who met established poverty income and nutritional
lected for measurement of plasma ferritin, transferrin receptor risk criteria (3); postpartum nonlactating women fall sixth in the
(TfR), and hemoglobin (Hb). 7-point priority system, behind pregnant and lactating women,
Results: The mean (±SE) Hb concentration of participants infants, and children. One of the most pervasive nutritional risks
exceeded that of nonparticipants from months 2 through 6. At in this population is iron deficiency.
6 mo, the mean Hb concentration of participants was signifi- Iron shortages are associated with adverse changes in many
cantly higher than that of nonparticipants (8.01 ± 0.12 and components of the immune system, including resistance to infec-
7.63 ± 0.12 mmol/L, respectively; P < 0.05) and the prevalence tion (4, 5) and changes in the function of the immune system, but
of anemia was significantly lower (17% and 51%, respectively; the exact consequences have not yet been determined (6).
P < 0.05). TfR and ferritin concentrations (consistently within Although there is no conclusive evidence that iron deficiency
the reference ranges) and dietary iron intakes did not differ signi- directly causes a higher incidence of infections, iron deficiency
ficantly between participants and nonparticipants and were not anemia and infections are prevalent in low-income populations
correlated with Hb concentrations. (7). Anemia, usually confirmed by a subnormal hemoglobin (Hb)
Conclusions: Our results suggest that WIC participants were concentration or hematocrit (for age and sex), may be caused by
significantly less likely to become anemic if uninterrupted post- infection and inflammation; laboratory changes are measurable
partum participation lasted for 6 mo. The lack of correlation even when the illness or infection is mild (8). Under these con-
among iron status indicators suggests that the lower mean Hb ditions, the release of stored iron is blocked, often resulting in
concentration in nonparticipants at 6 mo may not have been abnormally elevated ferritin and impaired delivery of iron to
related to improved iron status in participants but to other nutri-
ent deficiencies or differences in access to health care and health
and nutrition education. Am J Clin Nutr 2001;73:86–92. 1From the Department of Nutrition and Food Science and the Biometrics
Program,Department of Animal and Avian Sciences, University of Maryland,
KEY WORDS Hemoglobin, transferrin receptor, ferritin, College Park.
anemia, women, WIC, Special Supplemental Nutrition Program 2Supported by the University of Maryland and the Centers for Disease
for Women, Infants, and Children Control and Prevention (purchase order 0990-0115).
3Address reprint requests to PB Moser-Veillon, Department of Nutrition
and Food Science, University of Maryland, College Park, MD 20742.
INTRODUCTION 4Address correspondence to PR Pehrsson, Nutrient Data Lab,ARS/USDA,
10300 Baltimore Boulevard, Building 005, Room 309A, Beltsville, MD 20705.
The health of a woman during her reproductive years dramati- E-mail: ppehrsson@rbhnrc.usda.gov.
cally influences her health later in life, her fertility, her recovery Received August 24, 1999.
from pregnancy and childbirth, and the health of the children she Accepted for publication June 30, 2000.
86 Am J Clin Nutr 2001;73:86–92. Printed in USA. © 2001 American Society for Clinical Nutrition
POSTPARTUM NONLACTATING IRON STATUS 87
nationally recognized children’s store were awarded to the sub-
jects on completion of each visit.
On the basis of existing acceptance policies for postpartum
nonlactating applicants, 110 WIC-eligible women were recruited
for this study from Maryland WIC agencies. The study group
consisted of 57 WIC participants recruited from select Baltimore
City sites, which accommodated all nonlactating applicants
(Figure 1). The control group consisted of 52 WIC-eligible non-
participants recruited from Prince Georges County and 1 non-
participant recruited from Montgomery County. Postpartum risk
assessment for low-risk applicants in Prince Georges and Mont-
gomery County sites was based on the applicants’risk codes dur-
ing pregnancy. Because most English-speaking WIC participants
(both counties) were African American, only white and African
American women were recruited. Downloaded from https://academic.oup.com/ajcn/article/73/1/86/4729705 by guest on 06 January 2023
All subjects were free-living in an urban geographic location.
Eligibility criteria for inclusion in the study or control group
were 1) delivery of a full-term infant within the previous month,
2) absence of breast-feeding, 3) freedom from major medical
problems likely to affect the results (eg, heart disease and dia-
betes), and 4) qualification as a low-risk nonlactating postpartum
applicant or lack of adequate screening at the point of postpar-
FIGURE 1. Study design. Personal history includes information on tum recertification but previous certification (during pregnancy)
breast-feeding status; smoking status; maternal age; age at onset of men- with low-risk criteria codes. Women aged <19 y were excluded
struation; race; date of first prenatal visit; delivery weight; gestational because of the potential for the physiologic effects of growth to
duration and delivery date; number and ages of other children; number confound the results.
and dates of stillbirths, abortions, and miscarriages; participation in the The first visit (baseline) was conducted within 30 d of deliv-
Special Supplemental Nutrition Program for Women, Infants, and Chil-
dren (WIC) during pregnancy; participation in the Food Stamp Program; ery; each subject was interviewed to assess health and reproduc-
and use of vitamin and mineral supplements. tive history, past WIC participation, and characteristics of the
household. Height and weight were measured for each subject
and blood samples were drawn for the determination of Hb,
bone marrow for synthesis of heme (iron-deficient erythro- plasma TfR, and ferritin. Except for height, all measurements
poiesis) (9). However, in some cases iron stores may remain were repeated at 2, 4, and 6 mo postpartum (second, third, and
unchanged even if ferritin is elevated, and a misleading assess- fourth visits) and timed with recertification (first visit) and
ment of iron status may thus occur. voucher pickups (maternal-infant or infant) to maximize compli-
Numerous studies showed a positive effect of WIC participa- ance (Figure 1). Subjects with only one measurement were elim-
tion on the iron status of pregnant and lactating women and on inated from the analysis.
the pregnancy outcomes of low-income women (10–14). How- Much of the demographic and health background information
ever, evidence of the effect of participation on the iron status of was verified with WIC screening forms that had been completed
postpartum nonlactating mothers is lacking. The 1999 Review of during WIC recertification by a WIC staff member (Table 1).
the Nutritional Status of WIC Participants reported that nonlac- Self-reported weight at the first prenatal visit and weight at deliv-
tating postpartum participants continued to report low energy ery were recorded for each subject. Information on smoking sta-
and iron intakes [30% and 84% of the recommended dietary tus and use of vitamin and mineral supplements was documented
allowance (RDA), respectively] (15). This research was designed because of the potential effect of these practices on iron status.
to assess the effect of WIC participation on the postpartum iron Hemoglobin, transferrin receptor, and ferritin analysis
status of nonlactating women through measurement of Hb, trans-
ferrin receptor (TfR), serum ferritin, and iron intake over the Hb was measured in duplicate with a photometer system
6 mo after delivery. (HemoCue, Ängelholm, Sweden; 17); the Hb cutoff for anemia
classification was 120 g/L or 7.45 mmol/L, which is the gener-
ally accepted concentration for nonpregnant women (18–20).
SUBJECTS AND METHODS The instrument automatically reset itself to zero after each meas-
The Maryland WIC program served 89673 clients in financial urement and checked the intensity of the light source and the
year 1995 at a cost of $44 million (16). At the time of the study operation of the photocell. The instrument was calibrated with
(1994–1995), major cutbacks in federal funding required that the the control cuvette before each set of measurements.
Maryland WIC program admit postpartum women in selected The precision, accuracy, and reliability of capillary Hb
counties only if they were of high priority (eg, anemic). Risk measurements can be complicated by significant within-subject
profiles and criteria for WIC eligibility were consistent among variability, over both time and site to site, leading to potential
counties, enabling recruitment of the control group for this study. misclassification of iron status (21). For this reason, duplicate
The study was approved by the Human Subjects Review Boards Hb sampling was performed; if duplicates were highly variable
of the State of Maryland Department of Health and Mental or one measurement was in the anemic range and one in the
Hygiene and the University of Maryland. Gift certificates to a normal range, a third measurement was taken. For measurement
88 PEHRSSON ET AL
TABLE 1 Dietary intake
Demographic, health, and reproductive characteristics of nonlactating Assessment of supportive data on consumption of foods that
postpartum WIC participants and nonparticipants within 30 d of delivery1
affect iron status was performed with a low-literacy self-adminis-
Participants Nonparticipants tered food-frequency questionnaire (FFQ) designed for and tested
Baseline variable (n = 57) (n = 53) on women participating in WIC (24–26). The FFQ was used to
2 estimate the consumption of foods contributing iron and vitamin
Age (y) 24.9 ± 0.6 25.4 ± 0.6
Race C. The US Department of Agriculture (Agricultural Research Ser-
White 7 (13)3 12 (21) vice) Nutrient Data Bank was used to support the software for
African American 46 (87) 45 (79) determining nutrient intakes. We assumed that the 1989 RDA (6)
Onset of menses (y) 13.0 ± 0.2 13.6 ± 0.3 for nonpregnant women was appropriate for nonlactating women
Gynecologic age (y)4 12.4 ± 0.7 11.2 ± 0.6 postpartum, primarily because no other standards have been ade-
5
Family size quately documented and because the postpartum nonlactating
2–3 40 (70) 43 (81) state most closely matches the nonpregnant state.
≥4 17 (30) 10 (19)
Smoking status (cigarettes/d) Statistical analysis Downloaded from https://academic.oup.com/ajcn/article/73/1/86/4729705 by guest on 06 January 2023
0 43 (75) 46 (87) Data were analyzed with use of SAS, version 6.04 (27). Stu-
<10 10 (18) 3 (6) dent’s t tests were conducted to assess differences between par-
≥10 4 (7) 4 (7) ticipants and nonparticipants in time intervals between delivery
Gestation (wk)
<38 5 (9) 1 (2) and visits. Student’s t and chi-square tests were performed to
38–42 52 (91) 52 (98) assess differences at baseline and at each visit between the
6
Short interpregnancy interval 21 (39.6) 23 (40.3) 2 groups in smoking status, race, use of iron supplements, par-
Use of prenatal supplements 30 (53) 26 (49) ticipation in the Food Stamp Program, WIC participation, gesta-
during pregnancy tion, household size, and dietary iron intakes. Analysis of variance
Participation in food stamp program 28 (49) 24 (45) was conducted to assess differences in all iron-status indicators
1WIC, Special Supplemental Nutrition Program for Women, Infants when smoking status, participation in the Food Stamp Program,
and Children. use of iron supplements, and the length of the interpregnancy
2–
x ± SE. interval were considered. Because only a few women in either
3n (%). group smoked ≥10 cigarettes/d, heavy and moderate smokers
4Gynecologic age=date of most recent delivery age at onset of menses.
5Mother plus children. were combined. Partial correlation coefficients were determined
6Short interpregnancy interval = ≤2 y between prior pregnancy (full- between Hb, TfR, and ferritin measurements; univariate analysis
term infant, abortion, miscarriage, or stillbirth) and most recent pregnancy. of Hb was conducted to evaluate the normality of the distribu-
tion, identify potential outliers, and determine means. To allow
for the effect of missed visits on differences in Hb concentrations
of TfR and ferritin, 500 L whole blood was collected from between the groups, regression determinations of the slopes of
each subject into EDTA-treated vials from single finger sticks the lines for Hb measurements over time were computed for each
at each of the visits. The samples were stored on ice and trans- subject and these slopes were compared. Significant differences
ported to the University of Maryland. The blood was centrifuged in slopes were considered indicative of a group time interac-
for 10 min at 680 g and 4C and the plasma separated by tion. This is comparable with a repeated-measures analysis of
pipette into 2 labeled vials. Plasma samples were stored at variance except it is more powerful in that we assume that time
70C until analyzed. is continuous and that the change in Hb concentration with time
Plasma TfR was measured with the enzyme-linked immuno- is linear. Significance was set at P < 0.05.
sorbent assay (ELISA; Ramco Laboratories, Inc, Houston). A
best-fit straight line was generated from the standards by using
regression techniques. The cutoff of 8.5 mg/L was used to iden- RESULTS
tify subjects with iron deficient erythropoiesis or stage 2 iron Of the 110 subjects who completed the first visit, 94 (85%;
deficiency (22). Standards were measured during the study across 47 participants and 47 nonparticipants) completed at least the
15 standard curves: the 0 and SD of the normal control standard first and final visits. There were no significant differences
was 5.9 ± 0.6 mg/L (company-specified range: 5.6–10.4 mg/L); between groups in demographic, health, and reproductive char-
the CV was 10.8%. The 0 and SD for the high standards, meas- acteristics (Table 1). Eighty-four percent of the participants (48
ured across 18 standard curves, was 11.2 ± 2.3 mg/L (company- of 57) had received WIC vouchers during at least the last
specified range: 10.4–14.8 mg/L); the CV was 20.4%. trimester of their pregnancy; almost all of the nonparticipants
Plasma ferritin was measured by using an ELISA (Ramco (98%) had received WIC vouchers during their pregnancy.
Laboratories, Inc) (19, 21). A cutoff of 12.0 g/L (23) was used Because all but 2 nonparticipating subjects had participated in
to identify subjects with depleted iron stores or stage 1 iron defi- WIC during pregnancy, the effect of vouchers received during
ciency. A ferritin standard (Food and Agriculture Organization pregnancy on postpartum iron status could not be determined.
standard 80/578; World Health Organization International Lab Because of higher participation rates during pregnancy, nonpar-
for Biological Standards, Hertfordshire, United Kingdom) was ticipants received significantly more nutrition education before
measured in duplicate at concentrations of 9.1 and 91.0 g/L. The delivery than did participants (96% compared with 84%; P < 0.05).
lower concentration measured 9.2 g/L, or 101% of the true con- There were no significant differences in reproductive history
centration; the higher concentration measured 86.0 g/L, or 95% (age of onset of menses and gynecologic age) or in contraceptive
of the true concentration. practices between participants and nonparticipants (Table 1).
POSTPARTUM NONLACTATING IRON STATUS 89
TABLE 2 Iron measurements
Iron supplementation in nonlactating postpartum WIC participants and The mean Hb concentrations of participants and nonpartici-
nonparticipants1 pants by visit are shown in Table 3. The mean Hb concentration
Level of supplementation was the same between groups at the initial visit; over time, the
Month postpartum None ≥3 times/wk mean Hb concentration of participants tended to be greater than
n (% of group) that of nonparticipants (P < 0.05). In the 2 groups, the difference
2 increased with time; the maximum difference was significant 6 mo
0.5 postpartum (8.01 ± 0.12 compared with 7.63 ± 0.12 mmol/L; P <
Nonparticipants (n = 53) 31 (58) 22 (42) 0.05). As shown in Table 3, both means were above the Centers for
Participants (n = 57) 30 (53) 27 (47) Disease Control and Prevention cutoff for anemia of 120 g/L (7.45
3
2 mmol/L) (17) at 6 mo; however, a significantly higher percentage
Nonparticipants (n = 46) 39 (85) 7 (15) of nonparticipants than participants had concentrations below the
Participants (n = 48) 35 (73) 13 (27)
3 cutoff (51% and 17%, respectively; P < 0.05; Figure 2).
4
Nonparticipants (n = 45) 41 (91) 4 (9) One subject had an abnormally high mean Hb concentration
3 Participants (n = 46) 36 (78) 10 (22) of 10.06 mmol/L at 4 mo (6); another subject who had hemor- Downloaded from https://academic.oup.com/ajcn/article/73/1/86/4729705 by guest on 06 January 2023
6 rhaged soon after delivery had an initial mean Hb concentration
Nonparticipants (n = 47) 43 (92) 4 (9) of 3.66 mmol/L. These values were removed from the analysis
Participants (n = 47) 40 (85) 7 (15) but the subjects continued to participate in the study.
1WIC, Special Supplemental Nutrition Program for Women, Infants, Some evidence suggests that Hb concentrations are normally
and Children. lower in African American than in white persons (29–31). Most of
2Almost all taking supplements were taking prenatal supplements. the subjects in this study were African American; Hb data for
3Supplementation shifted from prenatal supplements to multivitamin those subjects were also analyzed separately. Because no univer-
plus iron. sally accepted race-specific cutoffs for anemia have been estab-
lished (29–31), the cutoff for anemia proposed by the Committee
Most of the nonparticipants had been terminated from WIC at on the Prevention, Detection, and Management of Iron Deficiency
the point of postpartum recertification because they had been Anemia Among US Children and Women of Childbearing Age of
coded as low risk during pregnancy and had had uneventful deliv- 112 g/d (31), or 6.95 mmol/L, was used. The mean Hb concentra-
eries with no indication of anemia. Ninety-one percent of the par- tion for African American subjects in this study tended to be lower
ticipants were coded as having inadequate diets (eg, deficient in (but not significantly lower) than the mean Hb concentration of the
specific nutrients or important food groups), the most common white subjects. The percentage of African American WIC partici-
criterion used for recertifying nonlactating applicants (28). pants who were iron deficient tended to be lower (but not signifi-
At the first visit, almost half of each group (47% of partici- cantly so) than that of African American nonparticipants 6 mo
pants and 42% of nonparticipants) used iron supplements, primar- postpartum (9% compared with 20%).
ily the remaining prenatal vitamins prescribed during pregnancy In both participants and nonparticipants, the mean Hb concen-
(Table 2). These percentages dropped dramatically to 15% of tration was significantly higher in smokers 4 mo postpartum, con-
participants and 9% of nonparticipants by 6 mo postpartum (no sistent with established adjustments for Hb concentration (18).
significant difference). Almost all supplement users were con- This strongly suggests that smoking had a strong influence in the
suming nonprescription multivitamins 6 mo postpartum. There assessment of iron deficiency in the population under study.
were no significant differences in supplement use between the No significant differences were found in mean TfR between
groups at any point during the study (Table 2). participants and nonparticipants through 6 mo postpartum. The
TABLE 3
Iron status of WIC participants and nonparticipants over the first 6 mo postpartum1
Month postpartum
Iron status 0.5 2 4 6
Hemoglobin (mmol/L)
Participants 7.88 ± 0.12 [57] 7.82 ± 0.12 [48] 7.88 ± 0.12 [46] 8.01 ± 0.12 [47]
Nonparticipants 7.88 ± 0.12 [52] 7.63 ± 0.06 [46] 7.70 ± 0.12 [44] 7.63 ± 0.12 [47]2
Transferrin receptor (mg/L)
Participants 6.5 ± 0.4 [57] 6.0 ± 0.3 [47] 5.8 ± 0.3 [46] 6.1 ± 0.3 [47]
Nonparticipants 7.2 ± 0.4 [51] 6.3 ± 0.3 [46] 6.0 ± 0.3 [45] 6.5 ± 0.3 [47]
Ferritin (g/L)
Participants 56 ± 5 [57] 47 ± 6 [48] 37 ± 4 [43] 36 ± 3 [45]
Nonparticipants 59 ± 7 [53] 45 ± 4 [46] 33 ± 3 [45] 35 ± 3 [46]
Ratio of transferrin receptor to ferritin
Participants 16.3 ± 1.6 [57] 23.2 ± 3.2 [47] 21.3 ± 2.0 [43] 22.2 ± 1.9 [45]
Nonparticipants 18.6 ± 1.7 [50] 23.4 ± 3.6 [46] 28.6 ± 4.2 [44] 28.7 ± 3.7 [46]
1 –
WIC, Special Supplementation Nutrition Program for Women, Infants, and Children. x ± SE; n in brackets. Groups matched for race and age but not
hemoglobin concentration. Statistical conclusions were based on linear regression procedures.
2Significantly different from participants, P < 0.05.
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