Rubella IgG

Rubella (German measles) is usually a mild viral illness, but its importance lies almost entirely in pregnancy: a rubella infection in early pregnancy can cause congenital rubella syndrome, with serious effects on the baby's heart, eyes, hearing and development. Because of this, rubella is one of the vaccines given in childhood (as part of MMR), and rubella IgG is the antibody used to confirm that a person is immune. A positive IgG means immunity — from past vaccination or, less commonly now, past infection — and generally lasts long term. The test's core use is preconception and antenatal screening: checking a woman's immunity so that, if she is found to be non-immune (IgG negative), she can be offered vaccination before pregnancy or after delivery (the vaccine is not given during pregnancy itself), and advised to avoid exposure meanwhile. It is also used in immunity checks for some healthcare workers. Unlike the IgM test (which would suggest a recent infection), the IgG test is not about diagnosing an illness but about documenting protection. So a positive result is the reassuring, desired outcome.

• Positive rubella IgG (immune) — protection against rubella from past vaccination or infection; the reassuring, desired result.
• A documented immune status — what antenatal and preconception screening aims to confirm.
• Positive IgM (a separate test) — would instead suggest a recent rubella infection, important in pregnancy.

• Negative rubella IgG (non-immune) — no protection; the person is susceptible to rubella.
• A non-immune result before pregnancy — vaccination can be offered beforehand.
• A non-immune result during pregnancy — the vaccine cannot be given then, so exposure is avoided and vaccination offered after delivery.