TABLE 1.
Characteristics of the analytical sample, stratified by low, intermediate and high maternal ferritin during pregnancy
| Low ferritin (SDS <−1, n = 387) |
Intermediate ferritin ( n = 1700) |
High ferritin (SDS >1, n = 392) | |
|---|---|---|---|
| Maternal characteristics | |||
| Ferritin, µg/L, mean (SD) | 20.6 (6.6) | 64.6 (24.3) | 170.3 (53.6) |
| Haemoglobin, g/dl, mean (SD) | 12.5 (0.8) | 12.6 (0.8) | 12.6 (0.8) |
| Age at enrolment, years, mean (SD) | 31.7 (4.6) | 31.4 (4.1) | 31.4 (3.6) |
| Pre‐pregnancy BMI, kg/m2, mean (SD) | 23.0 (3.6) | 23.2 (4.0) | 23.6 (4.0) |
| Estimated IQ, mean (SD) | 101.7 (12.5) | 100.9 (12.7) | 100.2 (12.5) |
| Education, tertiary, n (%) | 237 (61.6) | 1032 (61.6) | 248 (64.1) |
| Parity, primiparous, n (%) | 138 (35.8) | 1076 (63.4) | 325 (82.9) |
| Smoking during pregnancy | |||
| None, n (%) | 290 (80.8) | 1144 (73.6) | 261 (73.5) |
| Quit in early pregnancy, n (%) | 18 (5.0) | 160 (10.3) | 49 (13.8) |
| Continued, n (%) | 51 (14.2) | 250 (16.1) | 45 (12.7) |
| Alcohol use during pregnancy | |||
| None, n (%) | 125 (33.3) | 473 (29.2) | 84 (22.6) |
| Quit in early pregnancy | 60 (16.0) | 272 (16.8) | 71 (19.1) |
| Occasional, n (%) | 150 (40.0) | 678 (41.9) | 156 (41.9) |
| Weekly, n (%) | 40 (10.7) | 196 (12.1) | 61 (16.4) |
| Prenatal folic acid supplementation, n (%) | 288 (88.9) | 1270 (91.4) | 298 (94.3) |
| Prenatal multivitamin supplementation, n (%) | 101 (29.8) | 577 (38.8) | 122 (35.9) |
| Early‐pregnancy CRP <5 mg/L, n (%) | 232 (61.9) | 973 (58.6) | 214 (55.6) |
| Child characteristics | |||
| Sex, female, n (%) | 183 (47.3) | 863 (50.8) | 196 (50.0) |
| Characteristics at the 6‐year follow‐up | |||
| Age at cognitive assessment, years, mean (SD) | 6.1 (0.4) | 6.1 (0.4) | 6.1 (0.4) |
| Non‐verbal IQ, points, mean (SD) | 106.4 (13.2) | 105.1 (14.4) | 103.0 (15.0) |
| Language ability score, points, mean (SD) | 0.24 (0.93) | 0.26 (0.86) | 0.21 (0.94) |
| Characteristics at the 9‐year follow‐up | |||
| Age at motor assessment, years, mean (SD) | 9.8 (0.3) | 9.8 (0.3) | 9.8 (0.3) |
| Finger‐tapping score, taps, mean (SD) | 38.2 (6.5) | 38.3 (6.4) | 37.9 (6.5) |
| Balance performance score, steps, mean (SD) | 27.1 (8.1) | 26.8 (8.6) | 26.0 (8.9) |
| Characteristics at the MRI visit | |||
| Age at MRI, years, mean (SD) | 10.1 (0.6) | 10.1 (0.6) | 10.2 (0.6) |
| Total brain volume, cm3, mean (SD) | 1232.2 (102.6) | 1235.2 (105.8) | 1223.1 (117.4) |
| Cortical grey matter volume, cm3, mean (SD) | 592.4 (49.3) | 592.7 (51.5) | 586.6 (55.6) |
| Subcortical grey matter volume, cm3, mean (SD) | 60.8 (4.3) | 61.2 (4.4) | 60.9 (4.7) |
| Cerebral white matter volume, cm3, mean (SD) | 430.5 (47.3) | 432.2 (48.2) | 427.6 (52.6) |
| Cerebellar volume, cm3, mean (SD) | 146.3 (13.3) | 147.0 (12.6) | 145.7 (14.0) |
Abbreviations: %, proportion of cases in relation to all participants with data available; BMI, Body‐mass‐index; CRP, C‐reactive protein; IQ, Intelligence Quotient; MRI, Magnetic resonance imaging; n, number of cases; SD, Standard deviation; SDS, standard deviation score (ferritin and haemoglobin were standardised for gestational age at the time of venepuncture).