MS-2253

A 28-year-old woman, with two children, visits her doctor at 32 weeks gestation to receive her pertussis vaccine. She consents to participate in a research study that aims to assess the levels of immunoglobulins produced in response to the vaccine.

Following the vaccination, a specific immunoglobulin is observed to have a significantly elevated concentration. This immunoglobulin is capable of fixing complement and crossing the blood-placental barrier to enter the fetal circulation.

Which immunoglobulin is being referred to in this scenario?