More than 80% of pregnant women experienced iron deficiency by the third trimester of their pregnancies in an observational study published in the American Journal of Clinical Nutrition.
 
According to the authors of the study, while iron deficiency impacts a large proportion of pregnant women worldwide with potentially serious outcomes for mothers and infants, there is scarce data breaking down the prevalence of this deficiency.
 
The authors of the study set out to track iron deficiency rates in a group of more than 600 women who had low-risk, singleton pregnancies. Women with anemia at their first routine visit were excluded from analysis. At the 15-week visit, participants were interviewed by a research midwife to gather health information, including whether the participants were taking supplements containing iron. In total, 73% of participants took a supplement containing iron either pre-pregnancy or in the first trimester.
 
Blood measurements were taken at 15, 20, and 33 weeks into gestation. The prevalence of iron deficiency as less than 15 nanograms per liter increased from 4.5% to 13.7% and then 51.2%, at each respective visit. Using a ferritin threshold of less than 30 nanograms per liter, rates of iron deficiency were 20.7%, then 43.7%, and then 83.7% at the different time points, respectively. “A lack of consensus regarding biomarkers and thresholds used to define iron deficiency make it difficult to interpret findings across studies,” the authors noted.
 
Iron-containing supplements, mainly multivitamins, which were taken pre-pregnancy and in early pregnancy, were associated with a reduced risk of iron deficiency throughout the pregnancy, including in the third trimester, according to the authors. “This study highlighted a possible prophylactic role of multivitamin supplements that contain iron at lower doses. Concerns have been raised with the risk of excess iron following iron supplementation, but the nutrient dose contained in the supplements used by our participants was not associated with abnormally high ferritin concentrations.”
 
“Pregnancy places a remarkable strain on maternal iron status even in a high-resource, generally iron-supplemented population,” the authors of the study concluded. “Women should be screened early in pregnancy for iron status, with a suggested target ferritin concentration of over 60 nanograms per liter.”