Background and rationale {6a}
Untreated iron deficiency (ID) in pregnancy can lead to iron deficiency anaemia (IDA) [
1,
2]. ID in pregnancy is defined by low iron stores, measured by a level of circulating ferritin < 30 μg/L [
3‐
6]. Iron is essential for basic cellular processes, such as cell division and the synthesis of haemoglobin (Hb) [
7]. Anaemia in pregnancy is defined by a Hb level < 11.0 g/dL, WHO [
1,
5]. Thus, IDA in pregnancy is defined as Hb < 11.0 g/dL and serum-(
s)-ferritin < 30 g/μg/L.
In Danish pregnant women, who do not take iron supplementation, approximately 50% have ID and 21% have IDA [
8]. Anaemia (regardless the cause) is estimated to occur in 24% of Danish pregnant women (WHO).
The prevalence of ID is approximately 7% in 1st trimester, 14–40% in 2nd trimester, and 30–62% in 3rd trimester [
9,
10]. Prevalence of IDA is approximately 2% in 1st trimester, 8% in 2nd trimester and, 27% in 3rd trimester [
11,
12]. The steep increase in ID and IDA through the trimesters illustrates that women with ID in the beginning of pregnancy have a great risk of developing IDA during pregnancy.
National recommendations on routine iron supplementation in pregnancy do not necessarily prevent ID and IDA as seen in a Swizz study, where approximately 32% of pregnant women in 2nd trimester had ID and 6.2% IDA despite a recommended daily oral iron dose of 80 mg [
13].
Maternal symptoms of ID and IDA include fatigue/exhaustion, reduced physical performance, restless legs syndrome (RLS), and decreased ability to cope with blood loss during delivery. Severe anaemia may cause dizziness, shortness of breath, palpitation, orthostatism, and syncope [
14,
15]. Iron is an essential part of myoglobin, which explains why ID may compromise contractility in the uterine musculature that in turn may increase the risk for prolonged labour, caesarean section, and postpartum haemorrhage [
16,
17]. The consequence of maternal anaemia for the foetus is low birthweight, which can complicate the neonatal period [
18‐
21]. ID during foetal life may adversely affect brain development with long-term deficits. One trial showed that maternal anaemia in pregnancy could be linked to 14% of cases of mental retardation at a 7-year follow-up [
22].
Thus, isolated ID can be symptomatic and adversely affect foetal brain development. ID is a precursor for IDA, which is associated with maternal and foetal/neonatal morbidity. If treated early in pregnancy, the consequences of ID can be prevented.
In clinical practice, the standard treatment of ID and IDA in pregnancy recommended by the Danish Society of Obstetricians and Gynaecologists (DSOG) is oral iron supplementation in individualised doses based on screening values of Hb and ferritin in 1st trimester [
23].
Oral iron supplementation is associated with gastrointestinal adverse effects, affecting patient compliance [
14]. Thus, not all women treated with oral iron will respond to or comply with treatment. The recommendations are not clear on how to act in case of failure of the standard treatment. Thus, a pregnant woman with sustained ID will most likely be recommended to remain on oral iron and only receive intravenous (IV) iron if she becomes anaemic. However, it has not yet been investigated what treatment—intensified oral iron or IV iron—is most favourable in case the recommended standard treatment is not sufficient.
Treatment with intravenous ferric derisomaltose/iron isomaltoside 1000 (FDI) (Monofer®/Monoferric®, Pharmacosmos, Holbaek) is indicated when oral treatment is ineffective and when rapid iron delivery is clinically indicated. FDI is one of the newer IV iron formulations available. It was initially launched in Europe in 2010 and consists of iron and a carbohydrate moiety where the iron is tightly bound in a matrix structure. It is the matrix structure that enables a controlled and slow release of iron to iron-binding proteins, avoiding potential toxicity from release of labile iron [
24]. FDI has been studied in non-clinical reprotoxicology trials. In supra therapeutic doses, foetal malformations were seen in rabbits [Monofer® Investigators Brochure]. The risk for teratogenic or foeto-toxic effects is considered minimal at the proposed therapeutic dose. Several studies of FDI treatment of iron deficiency anaemia have been published without detected unexpected safety issues [
25‐
31]. FDI should be confined to second and third trimester if the benefit is judged to outweigh the potential risk for both the mother and the foetus [
6,
32,
33].
Ferrous fumarate containing ascorbic acid denotes a combination product administered in a film-coated tablet for oral ingestion. Ferrous fumarate is a ferrous salt. Ascorbic acid (vitamin C) facilitates iron uptake by maintaining iron in its ferrous form [
34,
35].
Previous trials have investigated the use of different IV iron preparations in pregnant women with IDA [
36‐
42]. We have not been able to identify trials investigating the use of IV iron for prevention of IDA in iron-deficient pregnant women. A recent trial where pregnant women with IDA were treated with the IV iron formulation ferric carboxymaltose reported a statistically significant improvement in Hb change from baseline in the IV iron group compared to oral iron group at 6 weeks. Overall hypersensitivity reactions were rare, IV iron treatment had a beneficial effect on Hb increase, and neonatal outcomes did not differ between groups [
40].
There are several reasons why it is important to systematically investigate if the use of IV iron is an effective and attractive mode of treatment in pregnancy compared to intensified oral iron treatment in women with sustained ID despite standard treatment: ID rarely resolves despite standard treatment, is unlikely to resolve later in pregnancy if still present after 4 weeks of standard care, is often left untreated in cases of intolerance to oral iron, is unfavourable for the foetus, and can progress into severe ID and IDA in later trimesters.
Therefore, measures to effectively treat ID early to prevent IDA are of great clinical importance.
Objectives {7}
In order to prevent IDA throughout the trial in pregnant women, who have ID after 4 weeks of standard treatment, the primary objective is to compare the efficacy of a single dose of IV administered FDI with a fixed dose of oral ferrous fumarate containing ascorbic acid.
The secondary objectives are to compare the effect of IV FDI and oral ferrous fumarate with ascorbic acid on (i) haematological indices of IDA in maternal blood, (ii) maternal fatigue and quality of life (QoL), (iii) RLS, (iv) the need for an additional IV FDI dose or (rescue) red blood cell (RBC) transfusion, and (v) safety.