Contemporary Screening and Treatment Practices for Iron Deficiency in Pregnancy

Introduction: There are discrepant definitions of both iron deficiency and anemia in pregnancy. It is recognized that iron requirements increase during pregnancy, particularly in the third trimester, and that deficiencies should be corrected to avoid adverse maternal-fetal outcomes. While low dose iron supplementation is recommended for all pregnant persons (ACOG Bulletin 233), dosing through prenatal vitamins varies widely. Additionally, despite the epidemic of iron deficiency in reproductive-age females globally and availability of high-value biomarkers (e.g., ferritin), current guidelines only recommend screening for iron deficiency during pregnancy in the presence of anemia. As anemia is the terminal manifestation of iron deficiency and reference ranges vary by organization, these guidelines and practices warrant further investigation and discussion.

Methods: Retrospective review and analysis of the electronic health record at Mayo Clinic (Rochester, MN) was performed for obstetric deliveries between June 2022 and May 2023. Iron deficiency was defined as a ferritin <50 mcg/L and anemia was defined as a hemoglobin <11 g/dL.

Results: A total of 2,141 unique deliveries were identified. The median age at delivery was 31 years old (range: 15 – 45) with 82% identifying as white. Anemia was documented in 42% (n=904) of pregnancies at least once throughout gestation, with an increasing frequency of 2% (n=43) in the first trimester, 11% (n=230) in the second trimester, 17% (n=361) in the third trimester, and 38% (n=803) from admission for delivery through the peri-partum period. There were five documented pRBC transfusions prior to admission for delivery; however, from admission for delivery through the peri-partum period, there were a total of 102 documented pRBC transfusions.

In total, 15% (n=318) of pregnancies were screened for iron deficiency through ferritin testing. Ferritin levels were measured 415 times with 23% (n=96) occurring between the last menstrual period and 12 weeks gestational age (WGA), 24% (n=100) occurring between 13-27 WGA, 40% (n=164) occurring between 28-40 WGA, and 13% (n=55) occurring post-partum. Iron deficiency was found in 70% (n=67), 79% (n=79), 80% (n=164), and 78% (n=43) of measured ferritin levels, respectively.

Despite the paucity of screening, prescriptions for oral iron increased throughout gestation with supplementation in pregnancy for 8% (n=170) prior to 12 WGA, 14% (n=290) for those 13-27 WGA, and 23% (n=489) for those 28-40 WGA. Similarly, intravenous iron infusions increased throughout gestation with supplementation in pregnancy for 0.3% (n=7) prior to 12 WGA, 0.7% (n=16) for those 13-27 WGA, and 4% (n=95) for those 28-40 WGA. Prenatal vitamins were documented in over 90% of pregnancies throughout gestation, although the majority were non-prescription and contained variable amounts of elemental iron.

Conclusions: Iron deficiency in pregnancy is underrecognized and undertreated. It follows that the accuracy of current reference ranges for anemia in pregnancy are suspect without rigorous verification of replete iron stores in the reference population. Given potential implications for blood product utilization and prenatal care, additional studies are warranted to better characterize iron deficiency in pregnancy as well as clinical sequelae for both mothers and infants. Simultaneously, discussions are needed around current guidelines and recommendations for both screening and treating iron deficiency in pregnancy. Providers, institutions, and professional societies should pursue pragmatic quality improvement initiatives and equitable healthcare delivery efforts to optimize care for this vulnerable patient population at high risk of iron deficiency.