Previous small-scale studies suggest that maternal smoking lowers neonatal body iron. Our objective was to study and compare the relationship between maternal and infants’ body iron in smokers and non-smokers in a large matched-pair cohort.
This was a prospective cohort study involving 144 mothers – 72 smokers and 72 non-smokers and their respective infants. Samples were obtained from maternal blood and infants’ cord blood at delivery for serum transferrin receptor (sTfR) and ferritin levels. Serum TfR and ferritin levels were measured by RAMCO ELISA and RIA assays. The total body iron (TBI) was calculated using the sTfR/ferritin ratio.
Maternal total body iron and smoking status
Women who smoked had lower sTfR, higher ferritin and higher body iron compared to nonsmoking women.
Infant’s total body iron, measurements at birth and smoking status
In contrast to their respective mothers, we found a small but statistically significant negative correlation between smoking and infants’ total body iron. The number of PPD smoked was negatively correlated with infants’ ferritin and total body iron. The number of days smoked during pregnancy was also negatively correlated with infants’ ferritin and total body iron and positively correlated with infants' sTfR.
Birth weight was lower in babies of smokers compared to nonsmokers (mean /- SD =3270 +/-475 vs. 3393 g +/- 475 g, p=0.03). Correlation studies revealed that birth weight in infants of smokers was negatively correlated with PPD smoked and number of days smoked. Birth length in the same infants was also negatively correlated with PPD smoked and number of days smoked.
Mothers who smoked during pregnancy had higher iron stores but their newborn infants had lower iron stores than those of non-smoking mothers. There may be a negative dose-dependent response between fetal smoke exposure and infant iron stores.
No relevant conflicts of interest to declare.
Iron status markers of smoker and non smoker pregnant women
| . | sTfR (mg/L) . | Ferritin (μ/L) . | sTfR/Ferritin . | Body iron (mg/kg) . |
|---|---|---|---|---|
| Non-smokers | 6.24 SD 3.67 | 30.3 SD 26.5 | 470 SD 647 | 3.8 SD 4.27 |
| Smokers | 5.02 SD 2.64 | 36.2 SD 27.6 | 361 SD 649 | 4.9 SD 4.09 |
| . | sTfR (mg/L) . | Ferritin (μ/L) . | sTfR/Ferritin . | Body iron (mg/kg) . |
|---|---|---|---|---|
| Non-smokers | 6.24 SD 3.67 | 30.3 SD 26.5 | 470 SD 647 | 3.8 SD 4.27 |
| Smokers | 5.02 SD 2.64 | 36.2 SD 27.6 | 361 SD 649 | 4.9 SD 4.09 |
Correlation between amount of smoking and smokers’ infants iron parameters and body measurements at delivery
| . | PPD smoked During Pregnancy . | Number of Days Smoked during Pregnancy . |
|---|---|---|
| Cord STfR | NS | r 0.175 p 0.039 |
| Cord Ferritin | r -0.172 p 0.044 | r -0.199 p 0.020 |
| Total Body Iron | r -0.168 p 0.048 | r -0.215 p 0.011 |
| Birth Weight | r -0.221 p 0.008 | r -0.230 p 0.006 |
| Birth Length | r -0.201 p 0.016 | r -0.166 p 0.047 |
| . | PPD smoked During Pregnancy . | Number of Days Smoked during Pregnancy . |
|---|---|---|
| Cord STfR | NS | r 0.175 p 0.039 |
| Cord Ferritin | r -0.172 p 0.044 | r -0.199 p 0.020 |
| Total Body Iron | r -0.168 p 0.048 | r -0.215 p 0.011 |
| Birth Weight | r -0.221 p 0.008 | r -0.230 p 0.006 |
| Birth Length | r -0.201 p 0.016 | r -0.166 p 0.047 |
NS=not significant
