When is the severity of neurological damage from toxoplasmosis most pronounced for a fetus?

The severity of neurological damage from toxoplasmosis is most pronounced during the first trimester. This is when the fetal neural structures are in the earliest stages of development, making the fetus particularly vulnerable to teratogenic effects. Exposure to the Toxoplasma gondii parasite during this period can disrupt the formation and development of the brain and central nervous system, leading to more significant and potentially irreversible damage.

Later trimesters have less severe impacts because many of the critical brain structures are already formed during the first trimester, and while infection can still pose risks, the neurodevelopmental outcomes are typically less severe than those encountered with early exposure. Additionally, at the time of delivery, the fetus may face risks from an active infection but would not necessarily experience the same level of direct neurological damage as seen in early pregnancy when the nervous system is developing.