During which stage of pregnancy is the risk of cytomegalovirus transmission to the fetus highest?

The risk of cytomegalovirus (CMV) transmission to the fetus is highest during the first trimester of pregnancy. During this period, the developing fetus is particularly vulnerable because the placental barriers are still establishing and the fetal organs are forming. CMV is a type of herpes virus that can be transmitted from a mother to her baby during pregnancy, and the earlier the infection occurs, the greater the chance of transmission.

While it is true that the severity of CMV infection can be greater if the virus is contracted later in pregnancy, the likelihood of transmitting the virus to the fetus diminishes as pregnancy progresses, with the highest rates of transmission observed when the mother contracts the virus in the first trimester. Additionally, transmission at or around birth can occur, but it is significantly lower compared to the early stages of pregnancy when the fetal development and immune system are still in formative stages.

Understanding the timing of CMV infection and its implications on fetal health is critical in neonatal intensive care as it can lead to serious developmental issues if transmission occurs.