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High iron deficiency prevalence yet 40% of pregnant women don’t get simple screening test

Half of pregnant women who had a simple blood test to check their iron stores had low iron levels, and one in four had severe iron deficiency, according to a paper published in the journal Blood Advances.

But despite how common iron deficiency is, 40% of pregnant women in this large regional study never had their iron levels checked, and women of lower socioeconomic status were less likely to get tested.

Researchers said the findings underscore the need to revisit clinical guidelines to ensure that ferritin testing, the standard measure of iron deficiency, is included as a routine part of maternal care and pregnancy health screenings.

One out of every two pregnancies is affected by iron deficiency, yet many women donʼt get a simple screening test to check

"Despite the very high prevalence of iron deficiency in pregnancy, and how easy it is to treat, we are not doing a very good job of checking for it," said lead study author Dr Jennifer Teichman of the University of Toronto, Canada and its affiliated hospitals including St Michael's Hospital/Unity Health Toronto, where the study was conducted. "It's not top of mind, in part, because of inconsistent recommendations for ferritin testing across clinical guidelines."

Iron requirements in pregnancy are high to support the developing foetus, the growing placenta, and the increased blood supply needed to sustain the pregnancy.

This demand for iron increases over the course of pregnancy. Iron deficiency is the most common cause of anaemia (low haemoglobin or red blood cell count) during pregnancy, which has been linked to poorer outcomes for both mother and baby, including a higher risk of premature delivery, low birth weight, post-partum depression, and even maternal death. Anaemia early in pregnancy has also been associated with neuro-developmental delays in the offspring, even as the child approaches school age and beyond, which points to potentially long- lasting effects.

Even low levels of iron alone can cause pregnant women to experience fatigue, weakness, and brain fog, Teichman explained.

The study included 44,552 pregnant women who received prenatal testing at community laboratories in Ontario, Canada, between 2013 and 2018 to determine how often ferritin testing was offered. Researchers also sought to provide more robust data about the prevalence and severity of iron deficiency among pregnant women and to identify whether certain clinical or demographic factors played a role in the likelihood of someone receiving a ferritin test.

Altogether, about 60% of patients got a ferritin test during pregnancy; 40% did not. Most tests were ordered by general practitioners (48%) and by obstetricians/gynaecologists (32%). The vast majority of ferritin testing (71%) occurred at or around the time of the first prenatal visit, when the risk of iron deficiency is lowest and, often, patients' iron levels were only checked once during their pregnancy.

"Iron deficiency becomes more common as women progress through pregnancy," said Teichman. "If we don't re-evaluate iron stores later in pregnancy, we miss a lot of women who are becoming iron deficient in later trimesters."

Teichman said the women in the study received care in Canada, a publicly funded health care system, which means patients don't incur the cost of ferritin testing. Despite this, they found that women of lower socioeconomic status were less likely to be tested for iron deficiency, which further underscores differences in access to care and how clinicians may treat these patients differently.

Based on their findings, she said pregnant women — and those planning to become pregnant — should ask about their iron levels before and during their pregnancy.

"Iron deficiency is very common, and there can be poor outcomes for both mom and baby if it isn't identified and treated," she said. "The good news is that it's easily found with a simple blood test and completely correctable with iron supplements." Standard prenatal vitamins by themselves cannot treat iron deficiency, she added.

"Prenatal vitamins contain only a sprinkling of iron and many combine iron with calcium, which can inhibit the absorption of iron. The way to address the problem is by identifying iron deficiency early on and then supplementing women with therapeutic doses of iron, which has 10 times the amount found in most prenatal vitamins."

Another important step would be to revise guidelines to ensure women were screened appropriately. Currently, the United States Preventative Services Task Force does not recommend universal screening for iron deficiency in pregnancy, citing the evidence as "insufficient to assess the balance of benefits and harms of screening for iron deficiency anaemia in pregnant women."

But, she explained, there were now sufficient data showing the harms of iron deficiency and anaemia in pregnancy, such that it would be unethical to conduct a study in which iron-deficient women are not given supplementation. Conversely, there are no conceivable harms to iron screening, she explained.

The study is limited to the Ontario region of Canada and didn't account for women who may have had a miscarriage, who received fragmented care, or were referred to a hospital-based obstetric practice. Information about patients' ethnicity and education levels was unavailable.

Study details

Suboptimal iron deficiency screening in pregnancy and the impact of socioeconomic status in a high-resource setting

Jennifer Teichman, Rosane Nisenbaum, Andrea Lausman, Michelle Sholzberg

Published in Blood Advances on 30 August 2021


Iron deficiency (ID) is the most widespread micro-nutritional deficiency in the world and disproportionately affects females due to increased iron requirements during menstruation, pregnancy and lactation. ID is the most common cause of anaemia in pregnancy. ID and ID anaemia (IDA) represent a spectrum that begins with depletion of iron stores and progresses to an inability to support proper red blood cell synthesis.

Estimates of the prevalence of ID among North American pregnant patients range from 16% to 77%, with rates increasing progressively across trimesters.

IDA has been associated with poor maternal and foetal outcomes including maternal fatigue, cognitive dysfunction, depression, low birth weight, premature delivery, childhood iron deficiency and anaemia and poor cognitive development in the child.

In two high-resource countries, maternal anaemia early in pregnancy has been associated with severe maternal morbidity and mortality, and with increased risk of intellectual disability, autism spectrum disorder and attention deficit/hyperactivity disorder in offspring.

Moreover, it has been shown that proper management of ID reduces the risk of maternal post-partum blood transfusions and improves neonatal birth weight.

Key Points
Iron deficiency (ID) affects over half of pregnancies in a high-resource setting, yet screening for ID is missed in 40% of pregnancies

Females of lower socioeconomic status (SES) have lower odds of ID screening in pregnancy compared to higher SES counterparts

Iron deficiency anaemia (IDA) in pregnancy is associated with poor maternal and childhood outcomes, yet ferritin testing, the standard test for iron deficiency (ID), is not considered part of routine prenatal bloodwork in Canada.

We conducted a retrospective cohort study of 44,552 pregnant patients with prenatal testing at community laboratories in Ontario, Canada to determine the prevalence of ferritin testing over five years. Secondary objectives were to determine the prevalence and severity of ID, and to identify clinical and demographic variables that influence the likelihood of ID screening. 59.4% of patients had a ferritin check during pregnancy; 71.4% were ordered in the first trimester, when the risk of ID is lowest.

Excluding patients with abnormally elevated ferritins, 25.2% were iron insufficient (30-44 µg/L) and 52.8% were iron deficient (≤29 µg/L) at least once in pregnancy. 8.3% were anaemic (haemoglobin <105 g/L). The proportion of anaemic patients with a subsequent ferritin test in pregnancy ranged from 22% to 67% in the lowest and highest anaemia severity categories, respectively.

Lower annual household income was negatively associated with the odds of a ferritin test; compared to those in the fifth (i.e. highest) income quintile, the odds of ferritin testing for patients in the first, second, and fourth quintiles were 0.83 (95% CI 0.74-0.91), 0.82 (95% CI 0.74-0.91), and 0.86 (95% CI 0.77-0.97), respectively.

These data highlight gaps in prenatal care and issues of health equity that warrant harmonisation of obstetrical guidelines to recommend routine ferritin testing in pregnancy.


Blood advances article – Suboptimal iron deficiency screening in pregnancy and the impact of socioeconomic status in a high-resource setting (Open access)


See more from MedicalBrief archives:


Inadequate iron intake affects infant brain development


Anaemia raises mortality risk in pregnant women


Low-cost, rapid test for iron and vitamin A deficiencies


Link between poor nutrition in pregnancy and HEV



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