Table 2.
Effect of the intervention with iron supplementation throughout pregnancy on stratum 1 (40 or 80 mg/d) and stratum 2 (40 or 20 mg/d) regarding fetal growth characteristics (outcomes) *.
| Fetal Growth Parameters | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Period of Fetal Growth Measurement and Iron Supplementation |
Estimated Fetal Weight (g) | Femur Length (mm) |
Head Circumference (mm) | Biparietal Diameter (mm) | Abdominal Circumference (mm) | |||||
| β (95% CI) | p Value | β (95% CI) | p Value | β (95% CI) | p Value | β (95% CI) | p Value | β (95% CI) | p Value | |
| Second trimester | ||||||||||
| Stratum 1 | ||||||||||
| Iron supplementation **: (40 mg/d (ref.) vs. 80 mg/d) |
1.43 (−4.40, 7.26) | 0.630 | −0.05 (−0.40, 0.30) | 0.780 | 0.26 (−1.14, 1.67) | 0.711 | −0.12 (−0.57, 0.33) | 0.588 | 1.26 (−0.03, 2.54) | 0.056 |
| Stratum 2 | ||||||||||
| Iron supplementation **: (20 mg/d (ref.) vs. 40 mg/d) |
1.54 (−7.44, 10.53) | 0.735 | 0.28 (−0.22, 0.79) | 0.267 | 0.03 (−1.52, 1.59) | 0.965 | 0.07 (−0.51, 0.65) | 0.813 | −0.58 (−2.55, 1.38) | 0.559 |
| Third trimester | ||||||||||
| Stratum 1 | ||||||||||
| Iron supplementation †: (40 mg/d (ref.) vs. 80 mg/d) |
−9.77 (−41.11, 21.57) | 0.540 | −0.30 (−0.75, 0.14) | 0.183 | −0.15 (−1.76, 1.46) | 0.855 | −0.32 (−0.78, 0.51) | 0.184 | −0.30 (−2.32, 1.72) | 0.767 |
| Stratum 2 | ||||||||||
| Iron supplementation †: (20 mg/d (ref.) vs. 40 mg/d) |
13.51 (−27.41, 54.47) | 0.515 | 0.03 (−0.57, 0.62) | 0.929 | −0.05 (−2.42, 2.31) | 0.963 | 0.13 (−0.66, 0.92) | 0.744 | 2.36 (−0.47, 5.19) | 0.103 |
| Birth parameters | ||||||||||
| Birthweight (g) | Length (cm) | Head circumference (mm) | ||||||||
| At birth | β (95% CI) | p value | β (95% CI) | p value | β (95% CI) | p value | ||||
| Stratum 1 | ||||||||||
| Iron supplementation †: (40 mg/d (ref.) vs. 80 mg/d) |
−14.74 (−90.37, 60.89) | 0.702 | −0.02 (−0.41, 0.38) | 0.939 | −0.21 (−0.53, 0.10) | 0.180 | ||||
| Stratum 2 | ||||||||||
| Iron supplementation †: (20 mg/d (ref.) vs. 40 mg/d) |
18.53 (−98.35, 135.52) | 0.755 | −0.24 (−0.82, 0.34) | 0.414 | −0.06 (−0.56, 0.45) | 0.823 | ||||
Results are from multivariable linear regression analyses, which were run separately for each fetal growth parameter and for each period (second trimester, third trimester, at birth). Values are regression β coefficient (β) and 95% confidence intervals (CIs) and reflect the difference in growth for each fetal parameter compared to iron supplementation group of 40 mg/d for stratum 1 and 20 mg/d for stratum 2. * All fetal growth parameter values were corrected for gestational age (weeks) at the time of ultrasound measurement or for gestational age (weeks) at birth using residual method. ** Model 1: adjusted for sex of baby, maternal age (years), maternal early-pregnancy BMI categories (normal weight (ref.), overweight, obese), family SES (low (ref.), medium, high), smoking during pregnancy (no (ref.), yes), fiber intake at the first trimester, log-serum ferritin (µg/L) at the first trimester, cortisol (µg/dl) at the first trimester, and carrier of HFE gene mutation (no (ref.), yes for stratum 2). † Model 2: model 1 and additionally adjusted for gestational weight gain (kg). Ref—reference.