Research Article: Hookworm-Related Anaemia among Pregnant Women: A Systematic Review

Date Published: September 17, 2008

Publisher: Public Library of Science

Author(s): Simon Brooker, Peter J. Hotez, Donald A. P. Bundy, Giovanna Raso

Abstract: Background and ObjectivesHookworm infection is among the major causes of anaemia in poor communities, but its importance in causing maternal anaemia is poorly understood, and this has hampered effective lobbying for the inclusion of anthelmintic treatment in maternal health packages. We sought to review existing evidence on the role of hookworm as a risk factor for anaemia among pregnant women. We also estimate the number of hookworm infections in pregnant women in sub-Saharan Africa (SSA).MethodsStructured searches using MEDLINE and EMBASE as well as manual searches of reference lists were conducted, and unpublished data were obtained by contacting authors. Papers were independently reviewed by two authors, and relevant data were extracted. We compared haemoglobin concentration (Hb) according to intensity of hookworm infection and calculated standardised mean differences and 95% confidence intervals. To estimate the number of pregnant women, we used population surfaces and a spatial model of hookworm prevalence.FindingsOne hundred and five reports were screened and 19 were eligible for inclusion: 13 cross-sectional studies, 2 randomised controlled trials, 2 non-randomised treatment trials and 2 observational studies. Comparing uninfected women and women lightly (1–1,999 eggs/gram [epg]) infected with hookworm, the standardised mean difference (SMD) was −0.24 (95% CI: −0.36 to −0.13). The SMD between women heavily (4000+ epg) infected and those lightly infected was −0.57 (95% CI: −0.87 to −0.26). All identified intervention studies showed a benefit of deworming for maternal or child health, but since a variety of outcomes measures were employed, quantitative evaluation was not possible. We estimate that 37.7 million women of reproductive age in SSA are infected with hookworm in 2005 and that approximately 6.9 million pregnant women are infected.ConclusionsEvidence indicates that increasing hookworm infection intensity is associated with lower haemoglobin levels in pregnant women in poor countries. There are insufficient data to quantify the benefits of deworming, and further studies are warranted. Given that between a quarter and a third of pregnant women in SSA are infected with hookworm and at risk of preventable hookworm-related anaemia, efforts should be made to increase the coverage of anthelmintic treatment among pregnant women.

Partial Text: Anaemia is a major factor in women’s health, especially reproductive health in developing countries. Severe anaemia during pregnancy is an important contributor to maternal mortality [1], as well as to the low birth weight which is in turn an important risk factor for infant mortality [2]–[3]. Even moderate anaemia makes women less able to work and care for their children [4]. The causes of anaemia are multi-factorial, including diet, infection and genetics, and for some of the commonest causes of anaemia there is good evidence of the effectiveness of simple interventions: for example, iron supplementation [5], long-lasting insecticide nets and intermittent preventive treatment for malaria [6]–[7].

Our literature searches identified 105 citations and from this list 30 potentially relevant research studies were identified; the remaining citations were either research studies among non-pregnant women, reviews or editorials. Of these 30 potentially relevant studies, 19 were determined to be eligible, including 13 cross-sectional studies, 2 randomised controlled trials, 2 non-randomised treatment trials and 2 observational studies.

That human hookworm infection results in intestinal blood loss which, in turn, can contribute to anaemia is well-established [8]. What has remained unclear and hindered public health policy and planning is the extent to which hookworm is associated with anaemia during pregnancy. The results of our systematic review quantify this relationship and confirm that heavy intensities of hookworm infection are associated with lower levels of haemoglobin than light infection intensities. This finding corroborates previous studies among school-aged children that show a relationship between infection intensity and haemoglobin [31]–[33].



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