WHO recommendation on preventive anthelminthic treatment

WHO recommendation on preventive anthelminthic treatment


In endemic areas preventive anthelminthic treatment is recommended for pregnant women after the first trimester as part of worm infection reduction programmes.

(Context-specific recommendation)


Publication history

First published: December 2016

Updated: No update planned

Assessed as up-to-date: December 2016



  • This recommendation should be considered alongside the recommendation on ASB diagnosis
  • This recommendation is consistent with the WHO Guideline: preventive chemotherapy to control soil transmitted helminth infections in high-risk groups (1), which states that:

 "Preventive chemotherapy (deworming), using single-dose albendazole (400 mg) or mebendazole (500 mg) is recommended as a public health intervention for pregnant women, after the first trimester, living in areas where both: (1) the baseline prevalence of hookworm and/or T. trichiura infection is 20% or more and (2) where anaemia is a severe public health problem, with prevalence of 40% or higher among pregnant women, in order to reduce the burden of hookworm and T. trichiura infection (conditional recommendation, moderate quality of evidence).”

  • Endemic areas are areas where the prevalence of hookworm and/or whipworm infection is 20% or more.
  • Anaemia is considered a severe public health problem when the prevalence among pregnant women is 40% or higher.
  • Infected pregnant women in non-endemic areas should receive anthelminthic treatment in the second or third trimester on a case-by-case basis (1). A single dose of albendazole (400 mg) or mebendazole (500 mg) should be used (1, 2).
  • The safety of these drugs in pregnancy has not been unequivocally established; however, the benefits are considered to outweigh the disadvantages (2, 3).
  • WHO recommends a treatment strategy comprising two treatments per year in high-risk settings with a prevalence of 50% for soil-transmitted helminthiasis, and once per year in areas with a 20–50% prevalence (1).
  • For further guidance on soil-transmitted helminth infections, refer to the WHO Guideline: preventive chemotherapy to control soil-transmitted helminth infections in high-risk groups (currently in press) (1).



Over 50% of pregnant women in LMICs suffer from anaemia, and helminthiasis is a major contributory cause in endemic areas (4). Soil-transmitted helminths are parasitic infections caused mainly by roundworms (Ascaris lumbricoides), hookworms (Necator americanus and Ancylostoma duodenale), and whipworms (Trichuris trichiura). These worms (particularly hookworms) feed on blood and cause further bleeding by releasing anticoagulant compounds, thereby causing iron-deficiency anaemia (5). They may also reduce the absorption of iron and other nutrients by causing anorexia, vomiting and diarrhoea (6).



The ANC recommendations are intended to inform the development of relevant health-care policies and clinical protocols. These recommendations were developed in accordance with the methods described in the WHO handbook for guideline development (7). In summary, the process included: identification of priority questions and outcomes, retrieval of evidence, assessment and synthesis of the evidence, formulation of recommendations, and planning for the implementation, dissemination, impact evaluation and updating of the guideline.

The quality of the scientific evidence underpinning the recommendations was graded using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) (8) and Confidence in the Evidence from Reviews of Qualitative research (GRADE-CERQual) (9) approaches, for quantitative and qualitative evidence, respectively. Up-to-date systematic reviews were used to prepare evidence profiles for priority questions. The DECIDE (Developing and Evaluating Communication Strategies to support Informed Decisions and Practice based on Evidence) (10) framework, an evidence-to-decision tool that includes intervention effects, values, resources, equity, acceptability and feasibility criteria, was used to guide the formulation and approval of recommendations by the Guideline Development Group (GDG) – an international group of experts assembled for the purpose of developing this guideline – at three Technical Consultations between October 2015 and March 2016.

To ensure that each recommendation is correctly understood and applied in practice, the context of all context-specific recommendations is clearly stated within each recommendation, and the contributing experts provided additional remarks where needed.

In accordance with WHO guideline development standards, these recommendations will be reviewed and updated following the identification of new evidence, with major reviews and updates at least every five years.

Further information on procedures for developing this recommendation are available here.


Recommendation question

For this recommendation, we aimed to answer the following question:

  • For pregnant women (P), does prophylactic anthelminthic treatment (I) compared with no intervention (C) improve maternal and perinatal outcomes (O)?


Evidence summary

The following evidence on the effects of prophylactic anthelminthic treatment was derived from a Cochrane review that included four trials conducted in Peru, Sierra Leone and Uganda, involving 4265 pregnant women (3). In two trials (Peru and Sierra Leone), the anthelminthic medication (albendazole or mebendazole) was administered as a single dose in the second trimester, with or without daily iron and folic acid supplements, irrespective of the presence of proven helminthiasis. The frequency of anaemia (Hb < 110 g/L) in these two trials was 56% and 47%, respectively, and the frequency of intestinal worms ranged from 20% to 64.2% for roundworm, 46.4% to 65.6% for hookworm, and 74.4% to 82% for whipworm. One small Ugandan trial administered a single dose of albendazole (400 mg) or placebo to women in the second trimester, irrespective of the proven presence of helminthiasis; baseline prevalence was 15%, 38% and 6% for ascariasis, hookworm and trichuriasis, respectively. The other Ugandan RCT contributed data on albendazole plus ivermectin versus ivermectin only, administered as single doses to pregnant women in the second trimester; all women were infected with an intestinal helminth at trial entry.

Maternal outcomes

Low-certainty evidence suggests that a single dose of albendazole or mebendazole in the second trimester of pregnancy may have little or no effect on maternal anaemia (defined as Hb < 11 g/dL) (4 trials, 3266 women; RR: 0.94; 95% CI: 0.81–1.10).

Fetal and neonatal outcomes

Moderate-certainty evidence indicates that a single dose of albendazole or mebendazole in the second trimester of pregnancy probably has little or no effect on preterm birth (2 trials, 1318 women; RR: 0.88, 95% CI: 0.43–1.78) or perinatal mortality (2 trials, 3385 women; RR: 1.09, 95% CI: 0.71–1.67). No other ANC guideline outcomes were reported in the review.


Additional considerations

None of the trials in the Cochrane review evaluated effects of more than one dose of anthelminthics. Findings from large non-randomized studies (NRSs) suggest that prophylactic anthelminthic treatment may have beneficial effects for mothers and newborns living in endemic areas (11, 12):

––One NRS, including approximately 5000 pregnant women in Nepal with a 74% prevalence of hookworm infection, reported a 41% reduction in six-month infant mortality among women receiving two doses of albendazole (one each in the second and third trimesters) compared with no treatment (95% CI: 18–57%) (11). This study also showed reductions in severe maternal anaemia with albendazole.

––A study from Sri Lanka involving approximately 7000 women compared mebendazole with no treatment and found fewer stillbirths and perinatal deaths among women receiving mebendazole (1.9% vs 3.3%; OR: 0.55, 95% CI: 0.40–0.77), and little difference in the occurrence of congenital anomalies (1.8% vs 1.5%, for intervention and controls, respectively; OR: 1.24, 95% CI: 0.80–1.91), even among the 407 women who had taken mebendazole in the first trimester against medical advice (12).

The WHO manual on Preventive chemotherapy in human helminthiasis stresses that every opportunity should be taken to reach at-risk populations through existing channels (2).

Cross-referencing other WHO guidelines, the upcoming 2016 WHO Guideline: preventive chemotherapy to control soil-transmitted helminth infections in high-risk groups recommends that a single dose of albendazole or mebendazole should be offered to pregnant women in the second and third trimesters of pregnancy where the prevalence of any soil-transmitted helminth infection (roundworm, hookworm and whipworm) exceeds 20% (1).

Preventive helminthic treatment helps to lessen the burden of other infections, e.g. HIV, malaria and TB, and contributes to a sustained reduction of transmission (3).


Preventive chemotherapy against helminthic infections is a cost–effective intervention. The market price of a single tablet of generic albendazole (400 mg) or mebendazole (500 mg) is about US$ 0.02–0.03 (2).


Helminthic infections are widely prevalent in povertystricken regions and control of this disease aims to alleviate suffering, reduce poverty and support equity (2).


Affected women are often asymptomatic and may not perceive the need for treatment. Therefore, the prevalence of soil-based helminthiasis in a particular setting is likely to influence women’s and providers’ preferences. Studies of anthelminthic programmes among non-pregnant cohorts, e.g. schoolchildren, in endemic areas have shown high levels of acceptability (13). For women receiving preventive treatment in endemic areas, worms are often visible in the stools the day after treatment, and this may reinforce the value of the intervention. However, where there are likely to be additional costs associated with treatment (high confidence in the evidence) or where the intervention is unavailable because of resource constraints (low confidence in the evidence) women may be less likely to engage with services (14).


In a number of LMIC settings providers feel that a lack of resources, both in terms of the availability of the medicines and the lack of suitably trained staff to provide relevant information, may limit implementation of recommended interventions (high confidence in the evidence) (14).


Further information and considerations related to this recommendation can be found in the WHO guidelines, available at:



Implementation considerations

  • The successful introduction of evidence-based policies related to antenatal care into national programmes and health care services depends on well-planned and participatory consensus-driven processes of adaptation and implementation. These processes may include the development or revision of national guidelines or protocols based on this recommendation.
  • The recommendation should be adapted into locally-appropriate documents and tools that are able to meet the specific needs of each country and health service. Modifications to the recommendation, where necessary, should be justified in an explicit and transparent manner.
  • An enabling environment should be created for the use of this recommendation, including changes in the behaviour of health care practitioners to enable the use of evidence-based practices.
  • Local professional societies may play important roles in this process and an all-inclusive and participatory process should be encouraged.
  • Antenatal care models with a minimum of eight contacts are recommended to reduce perinatal mortality and improve women’s experience of care. Taking this as a foundation, the GDG reviewed how ANC should be delivered in terms of both the timing and content of each of the ANC contacts, and arrived at a new model – the 2016 WHO ANC model – which replaces the previous four-visit focused ANC (FANC) model. For the purpose of developing this new ANC model, the ANC recommendations were mapped to the eight contacts based on the evidence supporting each recommendation and the optimal timing of delivery of the recommended interventions to achieve maximal impact.


Research implications

The GDG did not identify any priority question related to this recommendation



Related links

WHO recommendations on antenatal care for a positive pregnancy experience.

(2016) - full document and evidence tables

Managing Complications in Pregnancy and Childbirth: A guide for midwives and doctors

Pregnancy, Childbirth, Postpartum and Newborn Care: A guide for essential practice

WHO Programmes: Sexual and Reproductive health

Maternal Health




  1. Guideline: preventive chemotherapy to control soil-transmitted helminth infections in high-risk groups. Geneva: World Health Organization; 2016
  2. Preventive chemotherapy in human helminthiasis: coordinated use of antihelminthic drugs in control interventions: a manual for health professionals and programme managers. Geneva: World Health Organization; 2006 (http://apps.who.int/iris/ bitstream/10665/43545/1/9241547103_eng. pdf, accessed 26 September 2016).
  3. Salam RA, Haider BA, Humayun Q, Bhutta ZA. Effect of administration of antihelminthics for soil-transmitted helminths during pregnancy. Cochrane Database Syst Rev. 2015;(6):CD005547.
  4. The global prevalence of anaemia in 2011. Geneva: World Health Organization; 2015 (http://apps.who.int/iris/bitstream/ 10665/177094/1/9789241564960_eng.pdf, accessed 29 September 2016).
  5. Salam RA, Haider BA, Humayun Q, Bhutta ZA. Effect of administration of antihelminthics for soil-transmitted helminths during pregnancy. Cochrane Database Syst Rev. 2015;(6):CD005547.
  6. Controlling disease due to helminth infections. Geneva: World Health Organization; 2003 (http://apps.who.int/iris/ bitstream/10665/42707/1/9241562390.pdf, accessed 29 September 2016).
  7. WHO handbook for guideline development, 2nd edition. Geneva: World Health Organization; 2014 (http://www.who.int/kms/handbook_2nd_ ed.pdf, accessed 6 October 2016).
  8. GRADE [website]. The GRADE Working Group; 2016 (http://gradeworkinggroup.org/, accessed 27 October 2016).
  9. GRADE-CERQual [website]. The GRADECERQual Project Group; 2016 (https://cerqual. org/, accessed 27 October 2016).
  10. The DECIDE Project; 2016 (http://www.decide-collaboration.eu/, accessed 27 October 2016).
  11. Christian P, Khatry SK, West KP, Jr. Antenatal anthelmintic treatment, birth weight, and infant survival in rural Nepal. Lancet. 2004;364(9438):981–3.
  12. de Silva N R, Sirisena JL, Gunasekera DP, Ismail MM, de Silva HJ. Effect of mebendazole therapy during pregnancy on birth outcome. Lancet. 1999;353(9159):1145–9.Downe S, Finlayson K, Tunçalp Ö, Gülmezoglu AM. Factors that influence the use of routine antenatal services by pregnant women: a qualitative evidence synthesis. Cochrane Database Syst Rev. 2016;(10):CD012392
  13. Downe S, Finlayson K, Tunçalp Ö, Gülmezoglu AM. Factors that influence the use of routine antenatal services by pregnant women: a qualitative evidence synthesis. Cochrane Database Syst Rev. 2016;(10):CD012392
  14. Downe S, Finlayson K, Tunçalp Ö, Gülmezoglu AM. Factors that influence the provision of good quality routine antenatal care services by health staff: a qualitative evidence synthesis. Cochrane Database Syst Rev. 2016


Citation: WHO Reproductive Health Library WHO recommendation on preventive anthelminthic treatment. (December 2016). The WHO Reproductive Health Library; Geneva: World Health Organization.