Pre-Pregnancy Infection Screen (TORCH)

Some of the most damaging infections a baby can face are ones the mother never felt. Toxoplasmosis, rubella, cytomegalovirus (CMV), and herpes simplex virus (HSV) can all cross the placenta or pass to a newborn during delivery. When a first infection strikes during pregnancy, the consequences range from hearing loss and vision damage to brain injury and stillbirth. The window for prevention is before conception, not after.

This panel measures immunoglobulin G (IgG) antibodies, the long-lasting immune memory proteins your body makes after it has fought off an infection or responded to a vaccine. A positive IgG result means you have already been exposed and carry some degree of protection. A negative result means you are susceptible, and a first infection during pregnancy would pose the highest risk to your baby. Knowing your status before you conceive gives you time to vaccinate when a vaccine exists, adopt specific precautions for infections without vaccines, and set up monitoring plans with your provider.

What This Panel Reveals

The five IgG tests in this panel answer one question each: have you already encountered this pathogen? Together, they build a personalized risk map for pregnancy. Where you show immunity, you can breathe easier. Where you show susceptibility, you can act.

Rubella stands apart because it is vaccine-preventable. A negative rubella IgG means you lack protective antibodies, even if you were vaccinated as a child. Roughly 9% to 10% of women of reproductive age in the United States have lost rubella immunity over time, according to national antibody surveys. The measles, mumps, and rubella (MMR) vaccine cannot be given during pregnancy, so the only time to close this gap is before conception. A single booster dose restores immunity in the vast majority of recipients, and conception should be delayed at least four weeks afterward.

CMV is the most common infection passed from mother to baby during pregnancy in developed countries, affecting an estimated 0.5% to 0.7% of all live births in the United States. That translates to roughly 20,000 to 30,000 affected newborns every year. When a woman encounters CMV for the first time during pregnancy (a primary infection), the chance of the virus crossing the placenta is between 30% and 40%. Among those infected in the womb, about 10% to 15% show symptoms at birth, including hearing loss, vision problems, and developmental delays. Another 10% to 15% of infants who appear healthy at birth go on to develop late hearing loss in childhood. A positive CMV IgG before pregnancy tells you that a primary infection is off the table; a negative result means you should take hygiene precautions around young children, the most common source of CMV.

Toxoplasma gondii is a parasite found in undercooked meat and cat feces. In the United States, antibody testing shows that approximately 11% of women of childbearing age have been exposed, meaning roughly nine out of ten women are susceptible. The risk of transmitting the parasite to the fetus increases as pregnancy progresses: about 15% in the first trimester, 30% in the second, and 60% or higher in the third. However, infections earlier in pregnancy tend to cause more severe damage, including calcium deposits in the brain, hydrocephalus (fluid buildup in the brain), and vision loss. A negative IgG means you need to be meticulous about meat preparation, hand washing, and avoiding cat litter during pregnancy.

Herpes simplex virus types 1 and 2 (HSV-1 and HSV-2) pose their greatest threat to newborns during vaginal delivery when the mother is actively shedding virus. The most dangerous scenario is a new, primary HSV infection acquired near the time of delivery, which carries a transmission risk of 30% to 50%. A recurrent outbreak in a woman who already carries the virus carries a much lower risk, typically below 3%. Knowing your HSV antibody status before pregnancy identifies whether you are already a carrier (and at low risk for primary infection during pregnancy) or whether you have never been infected and should take precautions to avoid acquiring the virus from a partner who carries it.

How to Read Your Results Together

Each test returns either a positive (reactive) or negative (non-reactive) IgG result, sometimes with a numeric value and an equivocal (borderline) zone. The pattern across all five tests tells you where your immune defenses stand and where the gaps are.

Multiple negative results do not mean something is wrong. They simply mean you have not yet encountered those pathogens and should take targeted precautions during pregnancy. The value of this panel is knowing exactly where the gaps exist rather than guessing.

When Results Can Be Misleading

IgG antibodies reflect past exposure, not current infection. A positive IgG result does not tell you when the infection occurred. If you suspect a recent exposure, an IgM antibody test (which detects the early immune response to a new infection) would need to be added. For CMV and toxoplasma in particular, distinguishing a very recent primary infection from an old one matters, because only primary infections during pregnancy carry the highest fetal risk.

IgG levels can also sit in an equivocal or borderline range, meaning the lab cannot confidently call the result positive or negative. In that situation, repeat testing in two to three weeks, or adding an IgM test, can clarify your status. Medications that suppress the immune system or conditions that impair antibody production may also produce falsely low IgG levels.

For HSV, type-specific IgG testing is highly accurate for HSV-2 but somewhat less sensitive for HSV-1. A negative HSV-1 IgG does not completely rule out prior infection, though it remains the best available blood antibody screening tool.

Tracking Over Time

For most people planning one pregnancy, a single pre-conception screen is sufficient. If all results are positive, your immune status is unlikely to change. If any results are negative, your status at the time of that test is your baseline. You would not need to repeat the positive tests before a future pregnancy, but you may want to recheck any negative results if significant time has passed or if your exposure risk has changed.

Rubella is the exception. If you receive the MMR vaccine after a negative result, retesting four to eight weeks later confirms that you developed protective antibodies. In rare cases, a single vaccine dose does not produce lasting immunity, and a second dose is needed.

If you become pregnant without having been screened, the same tests can be drawn early in the first trimester. However, the power of this panel is greatest before conception, when vaccination and behavioral changes can still prevent infection rather than simply detect it after the fact.

What to Do with Your Results

A fully positive panel is straightforward: you carry antibodies against all five pathogens, and no special pre-pregnancy interventions are needed for these infections. Share the results with your obstetrician or midwife so they become part of your prenatal record.

Any negative result should prompt a conversation with your provider before conception. For rubella, the next step is vaccination. For toxoplasma, CMV, and HSV, there are no vaccines available, so the strategy shifts to behavioral precautions and, in some cases, serial monitoring during pregnancy. If your HSV results reveal that you are antibody-negative but your partner is antibody-positive, your provider can recommend suppressive antiviral therapy for your partner and advise on reducing transmission risk.

If any result falls in the equivocal range, add an IgM test for that pathogen or repeat the IgG in two to three weeks. Do not leave borderline results unresolved before conceiving. Consider pairing this panel with syphilis screening, hepatitis B and C testing, and HIV testing, all of which are recommended as part of standard preconception or early prenatal care.