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Hookworm-Related Anaemia among Pregnant Women: A Systematic Review

24 Oct 2008

Paul Chinnock

Source: PLoS Neglected Tropical Diseases (see original article)

Citation: Brooker S, Hotez PJ, Bundy DAP (2008). Hookworm-Related Anaemia among Pregnant Women: A Systematic Review. PLoS Negl Trop Dis 2(9): e291.

Anaemia affects large numbers of pregnant women in developing countries. It increases their risk of dying during pregnancy and delivering low birth weight babies. Hookworm infection is also common in these countries and, inevitably, some of those affected are pregnant women. But to what extent is hookworm responsible for anaemia in these women? Would improved hookworm treatment programmes be of benefit to them?

Brooker, Hotez and Bundy performed a systematic review of studies to answer these questions and found evidence indicating that increased hookworm infection intensity is associated with lower haemoglobin levels in pregnant women in poor countries. Their review is published in PLoS Neglected Tropical Diseases.

The authors followed the reporting checklist of the Meta-analysis of Observational Studies in Epidemiology (MOOSE) group (1). Their primary outcome analysis was haemoglobin concentration (Hb), and their hypothesis was that Hb concentration is associated with the intensity of hookworm infection.

The search for data produced 18 studies that met the pre-specified inclusion criteria: 13 cross-sectional studies, two randomised controlled trials, two non-randomised treatment trials and two observational studies. They found Hb levels to be higher in women who were not infected with hookworm than in those who were lightly infected; the standardised mean difference (SMD) was −0.24 (95% CI: −0.36 to −0.13). The SMD between women heavily 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.

The authors estimate that 37.7 million women of reproductive age in sub-Sahran Africa were infected with hookworm in 2005, including approximately 6.9 million pregnant women. This amounts to somewhere in the range a quarter to a third of pregnant women in the region.

Based on their findings, the authors argue that increased efforts should be made to increase the coverage of anthelmintic treatment among pregnant women.

The journal has also published a discussion article (2) which sets the findings of the systematic review in context. This article emphasises the multifactorial nature of anaemia in pregnancy and discusses the role of iron deficiency and other issues. It argues that multiple interventions will be needed to address the problem.

Reference

1. Stroup DF, Berlin JA, Morton SC, Olkin I, Williamson GD, et al. (2000) Meta-analysis of observational studies in epidemiology: a proposal for reporting. Meta-analysis Of Observational Studies in Epidemiology (MOOSE) group. JAMA 283; 2008-2012. Available from: http://www.ncbi.nlm.nih.gov/pubmed/10789670

2. Friedman JF, Acosta LP (2008). Toward Comprehensive Interventions to Improve the Health of Women of Reproductive Age. PLoS Negl Trop Dis 2(9): e295. doi:10.1371/journal.pntd.0000295. Available from: http://www.ncbi.nlm.nih.gov/pubmed/18820743

2008 Brooker et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Source

Title:
Hookworm-Related Anaemia among Pregnant Women: A Systematic Review.

Authors:
Brooker S, Hotez PJ, Bundy DA

References:
PLoS Negl Trop Dis 2008: Vol. 2 no. 9, pp. e291

Abstract:
BACKGROUND AND OBJECTIVES: Hookworm 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). METHODS: Structured 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. FINDINGS: One 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. CONCLUSIONS: Evidence 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.

PMID: 18820740
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