Original article
Anemia—prevalence and risk factors in pregnancy

https://doi.org/10.1016/j.ejim.2012.04.008Get rights and content

Abstract

Background

To assess the prevalence of decreased iron stores and anemia in pregnant women. To determine whether the risk factors: socio-demographic background, age, BMI, and parity are associated with abnormal hemoglobin concentrations and/or abnormal iron status.

Methods

A longitudinal study was carried out at the Department of Obstetrics, University Hospital of Zurich to establish the risk factors and prevalence of the decreased iron stores and anemia in early pregnancy. In order to determine the hematological parameters and ferritin levels, venous blood samples of 470 singleton pregnancies between 16 and 20 pregnancy weeks were collected. According to hemoglobin and iron status, the patients were divided into four groups: patients with iron deficiency anemia, patients with decreased iron stores, patients with anemia for other reasons and normal patients. The determinants socio-demographic background, age, BMI and parity were explored using multiple logistic regression analysis.

Results

The prevalence of decreased iron stores (ferritin < 20 μg/l) was observed in 31.8% of subjects (149/470) and anemia (Hb < 110 g/l) in 18.5% (87/470). The prevalence of iron deficiency anemia was higher among women coming from former Yugoslavia and developing countries (p = 0.004 and p = 0.012). In patients coming from developing countries, a significant increase of anemia for other reasons was observed (p = 0.027) and in patients older than 30 years, a significant increase of decreased iron stores (p = 0.018).

Conclusions

In our study population with low parity, the prevalence of abnormal hemoglobin and abnormal iron status was 50.2% (236/470), and socio-demographic background was the most important risk factor of anemia.

Introduction

Decreased iron stores and anemia affect a large proportion of the population in developing and industrialised countries, particularly risk groups like children, menstruating women and pregnant women. During pregnancy there is a significant increase in the amount of iron required to increase the red cell mass, expand the plasma volume and to allow for the growth of the feto-placental unit. In pregnant women not given supplementary iron, the hemoglobin concentration (Hb) of the maternal blood falls from a non-pregnant average of about 133 g/l to an average of about 110 g/l at 36 weeks [1]. The fall is steepest up to 20 weeks of gestation; the concentration remains fairly constant up to 30 weeks and then rises slightly thereafter [2]. Thus, any estimation of hemoglobin concentration taken after the 20th week of gestation will be reasonably representative of the fall induced by pregnancy. It is becoming clear that the best time to detect any perinatal risk associated with maternal anemia may be up until 20 weeks of gestation [3].

The prevalence of iron deficiency anemia (IDA) varies with age, gender and socio-demographic background. About 6–30% of women suffer from iron deficiency anemia during pregnancy. Previous studies showed that the risk of IDA is also increased with parity; nearly three-fold higher for women with 2–3 children and four-fold greater for women with 4 or more children [4], [5], [6], [7]. On the other hand, in the study by Idowu et al. anemia were more prevalent among primigravidae than the multigravidae (p > 0.05) [8]. In other studies the risk of anemia was increased in African-American and poor women [5], [9], [10]. However, Deegan et al. demonstrated that total dietary iron intake and lifestyle determinants make no significant impact on iron status [11]. In the study by Charles et al. body mass index (BMI), mid-upper arm circumference, and the number of antenatal care visits showed a statistically significant association with anemia [12]. Al-Mehaisen et al. showed that gestational age, BMI, history of previous surgery, and multivitamin intake during pregnancy were significantly associated with anemia [13]. The major determinants identified for anemia in Ethiopia are chronic illnesses, deficiency of iron and deficiency of folic acid [14], [15].

There is evidence that an absence of iron stores has adverse consequences on feto-placental development [16]. A reduction in body iron is associated with a decrease in the level of functional compounds such as hemoglobin. There is little doubt that iron supplementation during pregnancy improves maternal iron and hematological status in pregnancy and postpartum [17], [18]. Perinatal and maternal mortality is substantially higher in anemic pregnant women, especially if their anemia is severe, but it can also occur in cases of moderate anemia. Several studies have also described a positive correlation between maternal hemoglobin levels early in pregnancy and birth weight, Apgar score and duration of pregnancy [17], [18], [19].

In the present study, the prevalence of decreased iron status, iron deficiency anemia and anemia for other reason in 470 singleton pregnancies between 16 and 20 weeks of gestation was determined. The independent risk determinants for anemia; socio-demographic background, parity, body mass index (BMI) and age were investigated using multiple logistic regression analysis.

Section snippets

Study population

In 2006, 470 pregnant women were prospectively observed at the Department of Obstetrics, University Hospital of Zurich. Venous blood samples were taken for determination of hematological status and ferritin level between 16 and 20 weeks and for hemoglobin concentration before delivery. The patients were asked for their consent to participate in our study and the informed consent was obtained before study enrolment. The study was approved by the hospital's Ethics Committee. All patients presented

Results

The demographic characteristics are shown in Table 1. A low level of education was observed in 81.1% (381/470). There was a significant difference in the level of higher education (secondary/technical or University) between patients from Europe + North America and Yugoslavia (17.3% (27/156) vs. 2% (3/147; p = 0.001); and between patients from Europe + North America and developing countries (17.3% (27/156) vs. 1.8% (3/167; p = 0.001).

The mean hemoglobin concentration at the baseline was 118 ± 9 g/l and the

Discussion

In the present study, the prevalence of abnormal hemoglobin and abnormal iron status in mid-pregnancy was 50.2% (236/470); namely anemia in 18.5% (87/470) and decreased iron stores in 31.7% (149/470). Epidemiological surveys performed in European countries showed a prevalence of decreased iron stores from 25% to 92% and iron deficiency anemia from 6% to 30% in pregnant women [16]. Although routine iron supplementation is given during pregnancy in Switzerland, in our study a relatively high

Learning points

  • Decreased iron stores and iron deficiency anemia affect a large proportion of pregnant women in industrialised countries.

  • In patients coming from developing countries, a significant increase of anemia for other reasons was observed and in patients older than 30 years, a significant increase of decreased iron stores.

  • Pregnant women should be screened for decreased iron stores and iron deficiency anemia in the first trimester and given selective iron supplementation when appropriate. This may help

Conflict of interest statement

The authors state that they have no conflicts of interest.

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