Helminth Infections in Pregnant Women

Jill E. Weatherhead, MD; Laila E. Woc-Colburn, MD, DTM&H


March 14, 2014


Schistosomiasis has a global distribution with more than 207 million cases worldwide.[1] There are 3 species -- Schistosoma haematobium, Schistosoma japonicum, and Schistosoma mansoni -- that lead to varying clinical syndromes. In general, Schistosoma infection and subsequent egg deposition generates a human immunologic response creating granulomatous inflammation and fibrosis in human tissues.[8]

Currently, data are inadequate to address schistosomiasis during pregnancy. Pregnancy schistosomiasis-associated morbidity is not included in global disability estimates.[8] However, it has been estimated that 10 million women yearly in Africa have schistosomiasis during pregnancy.[8]

S haematobium, which resides in the venous plexus surrounding the urinary bladder in humans, is the causative agent for two thirds of schistosomiasis cases. Adult S haematobium worms deposit eggs into the venules, which subsequently penetrate into the bladder, uterus, cervix, or vagina, resulting in granulomatous inflammation and bleeding. Schistosoma genitourinary disease includes cystitis, ureter obstruction, pyelonephritis, kidney failure, salpingitis, fallopian tubal obstruction, and ectopic pregnancy.[1,8,11] Lesions in the lining of the genital tract mucosa, termed "sandy patches," represent granulomas formed around a deposited egg and are also visible in genitourinary schistosomiasis.[1]

Schistosomiasis and Pregnancy

The effects on both mother and fetus can be socially and medically devastating. Women often have severe pain, stress incontinence, dyspareunia, and infertility and are at an increased risk of acquiring acute HIV infection if "sandy patches" are present along the vaginal mucosa.[1,8] Women also suffer from anemia as a result of direct blood loss, typically experiencing hematuria or vaginal bleeding, and anemia of chronic disease resulting from chronic inflammation.[8] Severe anemia can affect not only maternal morbidity and mortality but also reduce birth weight in offspring.[10]

Rodent models using females with moderately infected schistosomiasis have shown low-birth-weight offspring, increased rates of abortion, increased maternal death, and increased fetal and infant death in the experimental group vs the control group.[8] Furthermore, in animal models, congenital transmission of S japonicum has been demonstrated in piglets when a sow was infected during mid- to late pregnancy with schistosomes, and S haematobium eggs have been recognized in placental blood.[8,11] Despite the evidence from animal models, outcomes of human infants exposed prenatally to Schistosoma infections remain unclear.[8]

Treatment with praziquantel is currently being used in endemic areas with mass treatment programs. However, it is critical that girls receive medication at a young age and at repeated intervals, because once genital urinary lesions develop they are no longer reversible.[1] Infection during pregnancy is also treated with praziquantel, which has been approved by the WHO.[1] As a result of concerns surrounding the safety profile of praziquantel during pregnancy, some schistosome-endemic countries have not adopted this recommendation.[8]


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