Influence of maternal adiposity on iron status in pregnancy, early postpartum, and the neonatal period: A systematic review

Context: Obesity and iron deficiency are highly prevalent in pregnancy, and both can severely affect obstetric outcomes. However, the influence of obesity on iron status during the critical stages of pregnancy, postpartum, and the neonatal period remains unclear.

Objective: This systematic review seeks to examine the influence of adiposity on markers of iron status during pregnancy, postpartum, and the neonatal period.

Data sources: MEDLINE, EMBASE, Web of Science, CINAHL and Scopus databases were searched with no date restrictions. Observational or intervention human studies were included, assessing the association between adiposity and iron status in pregnancy, postpartum <6 weeks after birth, and newborns <28 days of age.

Data extraction: Screening of titles/abstracts/full text, data extraction and quality assessment were performed by two independent reviewers.

Data analysis: Seventy-six studies met the selection criteria of which sixty-one were classified as having a low risk of bias. Fourteen assessed iron status in the first trimester, twenty-four in the second trimester, twenty-four in the third trimester, sixteen in fetuses/newborns, and one in the postpartum period. Adiposity was primarily assessed by calculating BMI (n=58, 95%). The following was found in women with obesity compared to those without obesity: in the first
trimester, most studies reported similar or lower hemoglobin concentrations, similar ferritin concentrations, and higher soluble transferrin receptor (sTfR); in the second trimester, there was a trend toward increased hemoglobin, and sTfR, as well as decreased serum/plasma iron, with no differences in ferritin, transferrin saturation, or hepcidin; in the third trimester, most studies showed similar concentrations of iron markers but lower ferritin concentrations in umbilical cord blood/newborns.

Conclusions: Obesity impacts iron status during pregnancy and in newborns, with the most pronounced effects occurring in the first and second trimesters and in the neonatal period.