PCR for CMV, toxoplasmosis, others

Amniocentesis can help check if a baby has caught certain infections in the womb, especially cytomegalovirus (CMV) and toxoplasmosis, which can sometimes affect the baby’s brain, eyes, hearing, or overall development.​

How common?

• CMV is one of the most common infections in pregnancy; about 1% of pregnant women experience a first-time CMV infection, and a proportion of these infections are passed to the baby.​

• Toxoplasmosis in pregnancy is less common, with new infection in about 0.2% of pregnancies and an estimated 1–2 babies in 10,000 births affected by congenital toxoplasmosis.​

When amniocentesis is advised

• Amniocentesis may be recommended if the mother has blood tests suggesting a recent CMV or toxoplasma infection, especially in early or mid-pregnancy.​

• It is also considered if an ultrasound scan shows features that raise concern for infection, such as brain changes, enlarged brain cavities, calcifications, growth problems, or abnormal bowel findings.​

Purpose of the amniocentesis

• During amniocentesis, a thin needle is used to remove a small amount of the fluid around the baby (amniotic fluid); this fluid contains the baby’s cells and traces of infection if the baby is affected.​

• The fluid is tested by sensitive laboratory methods (such as PCR) to detect the genetic material of CMV or toxoplasma, which confirms whether the baby is truly infected or not.​

If the result is positive

• A positive result means the baby has caught the infection, but it does not automatically predict how severely the baby will be affected; follow-up detailed ultrasounds and sometimes fetal MRI are used to look for signs of damage or complications.​

• Depending on the findings and local practice, options may include close monitoring of the pregnancy, discussion of antiviral treatment for CMV, consideration of antibiotic treatment for toxoplasmosis, and careful counselling about prognosis and choices for the pregnancy and after birth.​

If the result is negative

• A negative result is very reassuring and usually means the baby has not been infected, even though the mother had CMV or toxoplasma during pregnancy.​

• In this situation, routine pregnancy care continues, often with some additional ultrasound monitoring, and parents are reassured that long‑term problems from CMV or toxoplasma infection are very unlikely.​