Fig 1.
Life cycle of Schistosoma haematobium with emphasis on urogenital involvement.
Schematic showing the S. haematobium life cycle in a pregnant host and a hypothesized pathway to placental involvement. After contact with contaminated freshwater, cercariae penetrate the skin, then enter blood vessels to be transported to the heart from where they reach the systemic circulation. Schistosomula mature in the liver, then adult worms typically migrate to pelvic venous plexuses (vesical, uterine, vaginal). Female worms release eggs that either pass into the bladder for excretion via urine or become entrapped in adjacent tissues. In rare cases, eggs may reach the placenta through interconnected venous plexuses of the urogenital tract and therefore, the gravid uterus.
Fig 2.
Flow diagram of screening, group allocation, follow-up, and placental results. Of 318 pregnant women screened by urine microscopy, 40 were positive for S. haematobium (infected group) and 278 were negative. A subset of negatives (n = 40) formed the non-infected control group; the remaining negatives (n = 238) were not followed up further. Placental tissue was available at delivery from 28 infected and 20 control participants (lost to follow-up: n = 12 and n = 20, respectively). Placental schistosomiasis—defined as the presence of S. haematobium eggs in placental tissue—was detected in 4/28 infected participants and 1/20 controls; the remainder were negative (24/28 and 19/20).
Table 1.
Maternal S. haematobium infection as defined by presence of eggs in urine cross-tabulated by placental schistosomiasis and age.
Table 2.
Number of eggs detected in macerated placental tissue samples (full-thickness bioptic placenta sections) and maternal urine among the five women with placental schistosomiasis.
Fig 3.
Female genital tract and placental schistosomiasis.
Adult S. haematobium pairs reside within pelvic venous plexuses (vesical, uterine, vaginal). This schematic is intended to support anatomic plausibility and does not imply a single proven route of egg migration. Schematic of the female genital tract and placenta highlighting anatomic sites affected by urogenital schistosomiasis due to S. haematobium. Eggs may get entrapped in the lower genital tract (vulva, vagina, cervix) and the upper tract (endometrium/myometrium, fallopian tubes, ovaries). The placenta panel depicts the maternal and fetal sides of the placenta, with the intervillous space; S. haematobium eggs may be found on the maternal side.