Abstract
Lassa fever is a zoonotic infection endemic to West Africa and is known to have adverse effects in pregnancy. We sought to synthesize and critically appraise currently available evidence on the effects of Lassa fever in pregnancy. An exhaustive bibliographic search from dates of inception to 30 September 2019 yielded 13 studies, from which individual patient data were extracted. The absolute risk of maternal death associated with Lassa fever was estimated at 33.73% (95% CI 22.05 to 46.42%, I2=72.40%, p=0.0014). The relative risk of death in pregnant women compared with non-pregnant women was estimated at 2·86 (95% CI 1.77 to 4.63, I2=27.27%, p=0.239). The formal gap analysis shows imprecise data on the risk of Lassa-related maternal and perinatal mortality and insufficient data for other pregnancy outcomes. The currently available evidence for the use of ribavirin in pregnant patients is not conclusive. With a threefold increased risk of mortality, there is a need to prioritize pregnant women as a special subgroup of interest for Lassa research. Robust prospective studies estimating the true incidence of adverse maternal and perinatal outcomes and randomized controlled trials to evaluate the efficacy of therapeutics for maternal Lassa virus infection are urgently needed.
Highlights
Lassa fever is a zoonotic infection endemic to West Africa
An initial search of systematic review databases showed that there was no systematic review on the effects of Lassa fever during pregnancy
We identified a total of 3610 records and excluded 1371 due to lack of primary data and inapplicability to the review objectives (Figure 1)
Summary
Lassa fever is a zoonotic infection endemic to West Africa. Most infections are asymptomatic with estimates of over 300 000 infections occurring in the region each year.[1,2] In the general population, mortality rates range from 1–2% in mild cases[2,3] to 15–20% in severe cases.[3,4,5] The crude case fatality rate in confirmed cases, in the 2019 Lassa fever outbreak in Nigeria, was 21.4%.6. Reports of Lassa fever in pregnant women indicate a poorer prognosis with maternal case fatality rates ranging from 7% in early pregnancy to 30% in late pregnancy.[7] Neonatal and fetal losses are reportedly high at 75 and 92%, respectively, with most fetal losses occurring in early pregnancy.[7]
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