Effects of Iron and Vitamin A Levels on Pregnant Women and Birth Outcomes: Complex Relationships Untangled Using a Birth Cohort Study in Uganda

Abstract

Introduction Women and infants are among the most vulnerable groups for micronutrient deficiencies. Pregnancy micronutrient status can affect birth outcomes and subsequent infants’ growth. Methods We determined the relationship between maternal iron and vitamin A status at delivery using several biomarkers (ferritin, soluble transferrin receptor [sTFR], body iron stores [BIS], hemoglobin and retinol binding protein [RBP]) and birth outcomes (body weight, Z-scores, head circumference, small-for-gestational-age and preterm birth) in rural Uganda. We investigated women who had serum results at the point of delivery and paired them to their infants at birth (n = 1244). We employed multivariable linear and logistic regression, adjusting for clustering at the subcounty level to determine the relationship between maternal micronutrients and birth outcomes. Results After adjusting for relevant factors, we found that maternal iron status (ferritin and BIS) and anemia (hemoglobin) were not significantly associated with the assessed birth outcomes. However, there was a significant association between serum sTFR and preterm births (AOR: 0.67; 95% CI 0.48–0.94). For Vitamin A, we observed a significant positive association between RBP and length-for-age (LAZ) at birth (β = 0.12, p < 0.030). Discussion These findings indicate that the relationship between maternal iron status and birth outcomes needs to be further investigated, because depending on the biomarker used the associations were either in favor of an adverse birth outcome or not significant. Additionally, they confirm that higher maternal RBP levels could be beneficial for birth outcomes. Clinicaltrials.gov as NCT04233944.

Associations of maternal serum concentration of iron-related indicators with birth outcomes in Chinese: a pilot prospective cohort study

“…Although higher ferritin levels (> 90th percentile vs. 10th-90th percentile) tended to be associated with shorter body length, the p-value is marginal ( p = 0.055) rather than significant. Our findings were supported by several studies that found no significant associations between iron exposure and body length/height [ 25 , 41 ] or head circumference [ 22 , 23 , 25 ]. However, other studies have found positive [ 7 , 8 , 19 ] or negative [ 29 – 31 ] associations between iron exposure and these two anthropometric indicators.…”

“…Two systematic reviews [ 22 , 23 ] did not find any significant associations between iron supplementation (mostly combined with folic acid) and anthropometric indicators in infants, children, and adolescents. These results were further supported by several other studies investigating iron exposure from dietary intake [ 24 ], blood [ 25 ], and amniotic fluid [ 26 ]. Conversely, several studies have suggested potential adverse associations between higher blood or placental iron status and anthropometric indicators [ 27 – 31 ].…”

The association between umbilical cord blood fat-soluble vitamin concentrations and infant birth weight

“…Vitamin A is critical to ensure proper embryonic development and is involved in several metabolic pathways (18). Observational studies have found that cord blood and maternal vitamin A levels were significantly correlated with birth weight and length (19)(20)(21)(22). The largest study investigating untargeted metabolic profiles showed that cord blood vitamin A levels were associated with birthweight (23), after controlling for hereditary factors such as parental size.…”

Plasma Retinol Concentrations and Dietary Intakes of Mother–Infant Sets in Singleton versus Twin Pregnancy

“…However, vitamin A deficiency (VAD) remains one of the leading nutritional deficiencies worldwide, especially among pregnant women [9]. VAD during pregnancy can have various adverse consequences for both mothers and infants [10][11][12][13]. Studies have found an association between VAD and two adverse outcomes in mothers: maternal anemia [11] and night blindness [10].…”

“…VAD during pregnancy can have various adverse consequences for both mothers and infants [10][11][12][13]. Studies have found an association between VAD and two adverse outcomes in mothers: maternal anemia [11] and night blindness [10]. One possible explanation for the anemia is that vitamin A plays a role in the absorption and utilization of non-heme iron, and a deficiency in vitamin A can lead to anemia [11].…”