Ferritin levels at 15 weeks can detect third-trimester deficiencies
The protein indicates how much iron is stored in the body and is therefore a key indicator of iron levels during pregnancy.
“Screening for iron deficiency at any time during pregnancy is not routine,” wrote researchers from University College Cork, Ireland and the University of Minnesota. “The most recent recommendation from the United States Preventive Services Task Force states that ‘the current evidence is insufficient to assess the balance of benefits and harms of screening for iron deficiency anemia in pregnant persons.’”
They noted that anemia in pregnant women is associated with an increased risk of both adverse perinatal and maternal outcomes, including preterm birth, low birth weight, postpartum depression and postpartum hemorrhage.
As such, the study aimed to evaluate the longitudinal changes in iron biomarkers across pregnancy and prevalence of iron deficiency in first-time mothers in a high-resource setting and propose early pregnancy iron status cutoffs that predict iron deficiency in the third trimester.
“Although often thought of as a problem in low-resource areas only, recent studies have documented rates of 33-42% iron deficiency in high-resource settings,” the researchers wrote.
Study details
This longitudinal study was a secondary analysis of data from IMproved PRegnancy Outcomes via Early Detection that helped develop screening for preeclampsia.
It analyzed data from 629 pregnant women who attended three study visits (15, 20 and 33 weeks of gestation) at an Irish study site. During these visits, iron, total body iron and inflammatory markers were measured.
The researchers found that iron deficiencies increased throughout the pregnancies. At 15 weeks, 4.5% of participants had an iron deficiency; at 20 weeks, 13.7%; and at 30 weeks, 51.2%.
Only 4.3% of participant used a higher-dose iron supplement, while 76.3% took a multivitamin that contained iron either pre-pregnancy or during the first trimester. Participants who were taking the multivitamins with iron had a significantly lower prevalence of deficiency.
“Pregnancy places a remarkable strain on maternal iron status even in a high-resource, generally iron-supplemented population,” the researchers wrote. “Women should be screened early in pregnancy for iron status, with a suggested target ferritin concentration of >60 μg/L.”
This 60ug/L of ferritin or lower at 15 weeks helped predict an iron efficiency at 33 weeks (defined as less than 15 ug/L). Of note, none of the participants had anemia at the start of the study, but many had low iron levels by the end.
While few differences in inflammation and iron biomarkers were detected, the researchers found that α-glycoprotein (AGP) was mainly only elevated for those who had CRP of more than 10 mg/L.
"We observed little difference in iron biomarkers or AGP between those with CRP of ≤5 mg/L compared with those with CRP of ≤10 mg/L, with the most pronounced effect on iron biomarkers in those with CRP >10 mg/L," they wrote. "Interestingly, AGP was largely only elevated in participants with CRP of >10 mg/L. Current thresholds used for the nonpregnant population to identify inflammation may not be suitable during pregnancy."
The study also analyzed whether participants who were obese or smoking had differences in deficiencies. There was a higher prevalence of iron deficiency in those who smoked at 15 weeks gestation and a significantly higher rate at 20 weeks. Obese participants had no changes in iron deficiencies compared to normal BMI participants.
Source: The American Journal of Clinical Nutrition 2024, Sept. 26
doi: https://doi.org/10.1016/j.ajcnut.2024.08.010
“Longitudinal evaluation of iron status during pregnancy: a prospective cohort study in a high-resource setting”
Authors: McCarthy, E.K., et al.
