TABLE 1.
Infant and Family Characteristics
| Characteristic | PP (n = 288) | PI (n = 305) | IP (n = 298) | II (n = 305) | Pa |
|---|---|---|---|---|---|
| Infant characteristics at birth | |||||
| Male sex | 155/288 (54) | 141/305 (46) | 149/298 (50) | 158/305 (52) | .29 |
| Birth weight, g | 3373.3 ± 373.3 | 3368.2 ± 375.3 | 3329.5 ± 370.1 | 3379.8 ± 350.2 | .39 |
| Gestational age, wk | 39.7 ± 1.1 | 39.7 ± 1.1 | 39.8 ± 1.1 | 39.7 ± 1.1 | .69 |
| First/only child | 217/283 (77) | 235/298 (79) | 240/293 (82) | 231/300 (77) | .18 |
| ID: serum ferritin <75 µg/L or zinc protoporphyrin/heme >118 µmol/mol | 118/288 (41) | 127/305 (42) | 131/298 (44) | 127/305 (42) | .89 |
| Infant characteristics at 9 mo | |||||
| Age at testing, mo | 9.31 ± 0.42 | 9.29 ± 0.41 | 9.34 ± 0.49 | 9.25 ± 0.40 | .06 |
| 9-mo weight-for-age z score | 0.88 ± 1.02 | 0.79 ± 1.09 | 0.92 ± 0.98 | 0.97 ± 0.98 | .15 |
| Milk feeding patternb | .50 | ||||
| Only breast milk | 108/217 (50) | 115/238 (48) | 114/230 (50) | 134/237 (57) | |
| Breast milk and formula | 73/217 (34) | 78/238 (33) | 71/230 (31) | 70/237 (29) | |
| Only formula | 36/217 (17) | 45/238 (19) | 45/230 (20) | 33/237 (14) | |
| IDc | 195/286 (68)d,e | 179/298 (60)d,f | 204/296 (69)e | 175/300 (58)f | .01 |
| Anemia, hemoglobin <110 g/L | 129/286 (45)d | 101/298 (34)e | 118/296 (40)d,e | 119/300 (40)d,e | .05 |
| ID anemiag | 108/265 (41)d | 81/278 (29)e | 99/277 (36)d,e | 101/282 (36)d,e | .04 |
| Maternal and family characteristics | |||||
| Maternal age, y | 24.6 ± 4.0) | 24.8 ± 3.5) | 24.6 ± 3.8) | 25.1 ± 4.0 | .44 |
| Maternal education, high school or higher | 89/287 (31) | 115/299 (38) | 98/297 (33) | 96/302 (32) | .21 |
| Net family income, ≤50 000 yuan/y | 243/284 (86) | 245/300(82) | 236/288 (82) | 255/295 (86) | .27 |
| Maternal mood total score at 9 mo (maximum = 30, possible depression ≥10)h | 6.09 ± 4.54 | 6.06 ± 4.48) | 5.60 ± 4.37 | 6.38 ± 4.35 | .21 |
| Home Observation for Measurement of the Environment total score at 9 mo (maximum = 45) | 31.5 ± 4.0 | 31.8 ± 4.0 | 31.3 ± 4.0 | 31.5 ± 3.9 | .51 |
| Maternal ID: body iron <0 mg/kgi | 174/284 (61.3)d | 204/304 (67.1)d | 119/294 (40.5)e | 128/302 (42.4)e | <.001 |
Values are n/total (%) for categorical values and mean ± SD for continuous variables. The n values vary due to missing data. II, iron in pregnancy/iron in infancy; IP, iron in pregnancy/placebo in infancy; PI, placebo in pregnancy/iron in infancy; PP, placebo in pregnancy/placebo in infancy.
Analysis of variance for continuous variables, x2 test for categorical variables.
Feeding solid foods was generally initiated between 4 and 6 months of age. Solids were typically not iron fortified at the time.
ID was defined as ≥2 abnormal iron measurements (mean corpuscular volume <74 fl, zinc protoporphyrin/heme >69 µmol/mol heme, serum ferritin <12 µg/L).
Groups with same superscript do not differ; different letters indicate statistically significant difference (P < .05).
Groups with same superscript do not differ; different letters indicate statistically significant difference (P < .05).
Groups with same superscript do not differ; different letters indicate statistically significant difference (P < .05).
Anemia by cutoff defined as hemoglobin <110 g/L, and ID was defined as ≥2 abnormal iron measurements (mean corpuscular volume <74 fl, zinc protoporphyrin/heme >69 µmol/mol heme, serum ferritin <12 µg/L).
Maternal mood evaluated by using the Edinburgh Postnatal Depression Scale.26
Body iron was calculated by using serum ferritin and soluble transferring receptor (sTfR), according to the formula of Cook et al27: body iron (mg/kg) = – [log10(sTfR*1000/ferritin) – 2.8229]/0.1207.