Increased risk of cytomegalovirus transmission in utero during late gestation

Objective: To determine whether the rate of human cytomegalovirus transmiss ion in utero is related to the gestational age at the time of maternal infe ction. Methods: One hundred twenty-three pregnant women followed in our units betw een 1988 and 1998 were studied retrospectively. Each had developed a primar y infection with cytomegalovirus evidenced by a seroconversion, confirmed b y specific enzyme immunoassays. Infants were diagnosed by urine culture. Results: Regardless of gestational age at the time of maternal cytomegalovi rus seroconversion, the mean rate of intrauterine transmission was 57.5%. T here was a statistically significant difference between early seroconversio n (during the first trimester) and late seroconversion (during the third tr imester) (36.0% versus 77.6%; P <.001). The risk of transmission calculated for seroconversion during the second trimester was intermediate (44.9%). Conclusion: A statistically significant difference in the rate of intrauter ine cytomegalovirus transmission was observed according to the duration of pregnancy at which primary infection occurred. The rate of transmission inc reased with gestational age. (C) 1999 by The American College of Obstetrici ans and Gynecologists.