Researchers Urge Prenatal Screening for Toxoplasmosis


All pregnant women should undergo screening for Toxoplasma gondii infection once each trimester, and all newborns should be screened for congenital toxoplasmosis, Kenneth M. Boyer, M.D., and colleagues have recommended.

Even a thorough history fails to identify about half of pregnant women who have an acute infection, according to Dr. Boyer of Rush University Medical Center, Chicago. Only a serologic screening process would identify all infected women and newborns in time to administer the medical treatment necessary to prevent neurologic sequelae of the illness in these infants (Am. J. Obstet. Gynecol. 2005;192:564-71).

“It is difficult to imagine that any informed mother or father would choose not to include this screening in their prenatal care, considering that almost all untreated infants who are infected … in utero experience ophthalmologic and/or neurologic disease, and that treatment of the fetus and infant clearly reduces these risks,” they said.

The researchers retrospectively analyzed the medical records of 131 infants and children with congenital toxoplasmosis who were referred to the Chicago Collaborative Treatment Trial. The study focused on demographic data and the mothers' understanding of factors surrounding their exposure to the parasite.

The women were questioned about their exposure during pregnancy to cats, cat litter, gardening, and sandboxes. They also were questioned about their consumption of raw or undercooked meat, eggs, or unpasteurized milk, as well as the nature and timing of their exposure; and any illness during pregnancy that was compatible with infection, especially prolonged fever, night sweats, myalgia, headache, and lymphadenopathy.

Most of the women (75%) could recall a conceivable exposure, but only 39% specifically recalled exposure to cat litter or raw meat dishes. One-quarter of the women could not identify any possible exposure to either cats or raw or undercooked foods.

More than half (52%) could not recall an infectious illness of any kind during pregnancy. Almost half (48%) noted an illness that might have been caused by the parasite; 27% recalled fever or night sweats and 23% recalled lymphadenopathy.

Ten of the women had serologic testing for toxoplasmosis before delivery. Three of those were living in France at the time, where such testing is part of routine obstetric care. Each of the remaining seven women had compatible illness or identified risk factors. One woman was tested because an ultrasound noted ascites in her twin fetuses. Three were tested because their physicians were looking for the cause of the illness, and three were tested as part of routine obstetric care.

Since only three women were tested as part of an investigation of an infectious illness, it is apparent that many physicians do not consider toxoplasmosis as a possible cause of these nonspecific symptoms during pregnancy, the authors noted. “This observation points out the importance of greater recognition by obstetricians of the pediatric implications of maternal infection and infectious symptoms during pregnancy.”

The only way to prevent or detect a higher proportion of infants with congenital infection is by systematic serologic screening, they concluded, adding that cost analyses should be performed before any decision making occurs.

However, the potentially devastating lifelong effects of congenital toxoplasmosis, and the recognized benefits of early identification and treatment, make a compelling case for systematic screening, the researchers said.

Additionally, they noted, congenital toxoplasmosis is more common than many genetic and metabolic diseases, such as phenylketonuria, congenital hypothyroidism, and congenital adrenal hyperplasia, for which mandatory neonatal screening already exists.

The American College of Obstetricians and Gynecologists recommends routine toxoplasmosis screening only in HIV-positive pregnant women. Routine screening also may be justifiable in women who are cat owners, the college says.

ACOG does not recommend routine screening for every pregnant woman, because there is a low incidence of seropositivity in the United States. Countries such as France and Austria, which have mandated screening, have high rates of seropositivity among their populations.

Serologic screening in pregnant women may yield equivocal results because IgM antibodies to the parasite can persist for long periods, according to the American College of Obstetrics and Gynecologists.

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