Declining Malaria Transmission and Adverse Pregnancy Outcomes

Summary and Comment |
October 21, 2015

Declining Malaria Transmission and Adverse Pregnancy Outcomes

  1. Mary E. Wilson, MD

Although clearly beneficial, reducing malaria transmission decreases immunity in pregnant women and increases risk for adverse outcomes in those who are infected.

  1. Mary E. Wilson, MD

Impressive gains have been achieved in malaria control, but with reduced exposure comes delayed acquisition of immunity. Pregnant women and their offspring are unusually vulnerable to this disease.

To examine the consequences of decreased malaria transmission on pregnant women, investigators assessed the prevalence of Plasmodium falciparum infection in Mozambican women who delivered infants between 2003 and 2012, a period of marked decline in such transmission. The 1819 women involved in the study were participants in earlier clinical trials of antimalarial drugs (2003–2005, 2010–2012), during which specimens were obtained.

The prevalence of maternal malaria by microscopic exam at delivery decreased from 12% in 2003–2004 to 1% in 2010 but increased to 4% in 2012. By quantitative polymerase chain reaction assay, P. falciparum positivity decreased from 33% in 2003–2004 to 2% in 2010 but increased to 6% in 2012. Parasite densities in peripheral and placental blood were higher — and the malaria-related reduction in maternal hemoglobin was greater — in 2010–2012 than in 2003–2005. The malaria-associated reduction in birth weight was greater during the later years. Pregnancy-specific antimalarial antibodies also declined significantly over the study period. Although in 2003–2005 higher parity was associated with reduced parasite densities, in 2010–2012 densities were similar between primigravid and multigravid women.

Comment

The consequences of declining malaria prevalence are complex, and reduced transmission intensity can extend the age for symptomatic infection. This study clearly shows the adverse consequences for pregnant women and their offspring. Lower–birth-weight infants have a lower likelihood of survival. The weakening of antimalarial immunity also means that multigravid women may be as susceptible to malaria as primigravid ones. As noted by an editorialist, escalating parasite resistance to antimalarial agents (including sulfadoxine-pyrimethamine, which is administered for intermittent prophylactic treatment during pregnancy) increasingly hinders preventive efforts.

Editor Disclosures at Time of Publication

  • Disclosures for Mary E. Wilson, MD at time of publication Consultant / Advisory board GeoSentinel Surveillance Network (Special Advisor) Editorial boards UpToDate; Clinical Infectious Diseases; International Health; Infectious Diseases in Clinical Practice; Travel Medicine and Infectious Diseases

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