Congenital CMV infection is the most common congenital infection worldwide and a major cause of neurological impairment and sensorineural hearing loss. Fetal CMV infection is confirmed by a positive PCR test in the amniotic fluid (amniocentesis performed after 18–20 weeks of gestation and at least 8 weeks after maternal infection). However, despite a negative antenatal CMV PCR result, some newborns can be tested positive at birth. Although not widely documented, the prognosis for these babies appears to be good.

The aim of this study is to evaluate the long-term prognosis of fetuses with a false-negative AFS for cCMV, with a minimum follow-up period of 6 years.

This is a retrospective cohort study of false-negative amniocentesis reported at the CUB-Hôpital Erasme and Hôpital CHIREC in Brussels between 1985 and 2017.

Of the 712 negative CMV PCR amniocenteses, 24 had a CMV PCR positive at birth. The false negative rate was 8.6 %. Of the 24 cases, 9 primary maternal infections occurred in the first trimester, 14 in the second trimester and 1 in the third trimester. Among the 24 children, 2 had symptoms at birth (hyperbilirubinemia and left paraventricular cysts), but all had normal follow-up (minimum 4 years, mean 16,6 years).

Only 2 cases could be explained by early amniocentesis. Among the others, the false-negative results could be attributed to a low viral load, a delayed infection or, less likely, to a sample degradation.

Despite the false-negative results, all 24 children had a normal long-term follow-up.