Polymerase chain reaction (PCR) test for fetal toxoplasmosis

Polymerase chain reaction (PCR) is a method of duplicating DNA strands from a tiny sample of blood, hair, or tissue. PCR is used to identify infectious diseases, genetic conditions, and genetic links between people.

When a pregnant woman has toxoplasmosis, a PCR test on amniotic fluid is used to learn whether her fetus is also infected. PCR is preferred over a fetal blood test for antibodies because:1

  • Collecting amniotic fluid through amniocentesis is considered safer than fetal blood sampling.
  • PCR is better than antibody testing to detect toxoplasmosis.
  • PCR can be done earlier in a pregnancy than a blood test for antibodies. Because first- and second-trimester fetal infection carry the highest risk of birth defects and intellectual disability, earlier test results are important to parents who are considering ending such a pregnancy.

In rare cases PCR produces false-positive or false-negative test results. Follow-up testing and fetal ultrasound monitoring for hydrocephalus can help confirm PCR test results.

PCR is seldom used to diagnose toxoplasmosis in adults. Antibody testing of a blood sample is easier and more widely available.

Citations

  1. Davies JK, Gibbs RS (2008). Toxoplasmosis section of Obstetric and perinatal infections. In RS Gibbs et al., eds., Danforth's Obstetrics and Gynecology, 10th ed., pp. 346–350. Philadelphia: Lippincott Williams and Wilkins.

Last Updated: June 18, 2009

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