What this test measures
IgG antibodies for the 5 classical TORCH infections — indicating past exposure (and usually immunity) for each. Adding only IgG is cheaper than full IgM + IgG and is appropriate for pre-pregnancy / preconception screening to identify women who are non-immune to rubella (vaccine candidates), CMV (counsel about precautions), or HSV.
Why it matters
Pre-conception and early-pregnancy screening is when IgG-only TORCH is most useful: rubella IgG negative → counsel pre-pregnancy and offer MMR vaccination (one month before conception). CMV IgG negative → counsel on hygiene to reduce primary infection in pregnancy. Toxoplasma IgG negative → avoid raw meat, cat litter. HSV IgG positive → not concerning for vertical transmission except in active lesions at delivery.
How to prepare
No fasting required. Disclose pregnancy stage, MMR vaccination history, recent immunisations.
Markers & reference ranges
Reference ranges below are typical adult values. Your lab's reported range may differ slightly based on the assay platform and patient demographics — always read your report against the range printed on it.
| Marker | Normal range | If low | If high |
|---|---|---|---|
| Toxoplasma IgG (IU/mL) | > 7 = positive (past exposure) | Negative — susceptible; counsel about prevention (avoid raw meat, cat litter, contaminated soil). | Positive — past infection, generally protective. Maternal seropositivity before pregnancy is favorable. |
| Rubella IgG (IU/mL)[1] | ≥ 10 = immune | < 10 IU/mL — non-immune; recommend MMR vaccination pre-conception (avoid pregnancy 1 month after). | ≥ 10 IU/mL — immune from prior infection or vaccination. |
| CMV IgG (AU/mL) | Reactive (most adults positive) | Negative — susceptible; counsel on hygiene to reduce primary infection in pregnancy. | Positive — past infection. Reactivation risk in pregnancy is lower than primary infection. |
| HSV-1 IgG / HSV-2 IgG (reactive / non-reactive) | Non-reactive | Negative — no past HSV. | Positive — past infection. Manage active lesions at delivery (caesarean if active genital herpes; suppression from 36 weeks). |
IgG-only TORCH action by result
| Marker | Negative (susceptible) | Positive (immune / past) |
|---|---|---|
| Toxoplasma | Counsel: no raw meat, no cat litter | No action |
| Rubella | MMR vaccination pre-conception | No action — immune |
| CMV | Hygiene counselling in pregnancy | Lower risk; reactivation possible |
| HSV-1 / 2 | No action | Manage active lesions at delivery |
Frequently asked questions
Why only IgG, not IgM too?
IgG-only panels are cheaper and answer the most useful pre-conception question — "Am I immune or susceptible?". IgM is useful when acute infection is suspected; for routine pre-pregnancy screening it adds little.
Should I get this before getting pregnant?
Yes — pre-conception TORCH IgG identifies rubella non-immunity (vaccinate before conception) and CMV / toxoplasma non-immunity (counselling for behavioural prevention). It is more useful then than during pregnancy.
If I am rubella non-immune, what should I do?
Get MMR vaccination at least 1 month before trying to conceive. MMR is a live vaccine and contraindicated during pregnancy.
Will pregnancy lower my IgG?
Slightly — IgG dilutes with pregnancy plasma volume expansion (~30%). Borderline values can move; clear positives remain positive.
Is herpes IgG positive a problem?
Not for vertical transmission unless there is an active lesion at delivery. Recurrent genital herpes near term may warrant suppressive aciclovir from 36 weeks.
Related Immunology tests
Tests commonly ordered alongside TORCH-5 IgG, or that help interpret an unexpected result.
Sources & references
- RCOG — Antenatal Infection Screening · accessed 2026-05-30T00:00:00.000Z
- CDC — TORCH Infections · accessed 2026-05-30T00:00:00.000Z
- FOGSI — Antenatal Care · accessed 2026-05-30T00:00:00.000Z
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