Diagnosis of Rubella in Pregnancy

Serologic Confirmation Methods

The Centers for Disease Control and Prevention recommends diagnosing rubella in pregnant women through serologic confirmation using rubella-specific IgM antibody testing or demonstration of a significant rise in IgG antibody levels between acute and convalescent sera, with timing of specimen collection being critical for accurate results 1, 2
Draw the serum specimen between 1-2 weeks after rash onset for optimal IgM detection 1, 2
IgM antibody is less likely to be detected if the specimen is drawn earlier than 1 week or later than 4-5 weeks following rash onset 1, 3
False-negative IgM results may also occur even when specimens are appropriately timed 1, 4

Demonstrate a fourfold rise in IgG antibody titer between acute and convalescent specimens 1, 5
Draw the acute-phase specimen as soon after rash onset as possible, preferably within the first 7 days 1, 2
Draw the convalescent-phase specimen 10 or more days after the acute-phase specimen 1, 3
Test both specimens simultaneously in the same laboratory to ensure accurate comparison 1, 5

If the acute-phase specimen is drawn more than 7 days after rash onset, a significant antibody rise may not be detected by most commonly used tests 1, 2
In this scenario, complement fixation (CF) testing may be especially useful because CF antibodies appear later than HI, EIA, or IFA antibodies 1, 5
Obtain the acute-phase serum specimen as soon as possible after exposure 1, 3
Draw the convalescent-phase specimen 28 or more days after exposure 1, 4

Confirmation of rubella infection in pregnant women of unknown immune status following rash illness or exposure is often difficult, and serologic results are frequently nonconfirmatory 1, 4
Obtain a serum specimen as soon as possible when infection is suspected 1, 5
Perform prenatal serologies routinely to establish baseline immune status 1, 4
Request that laboratories performing prenatal screening retain specimens until delivery so that retesting can be done if necessary 1, 2

In adults, joint symptoms (arthralgia/arthritis) occur in up to 70% of infected women 6
The risk of congenital defects is up to 85% when infection occurs in the first 8 weeks of gestation 6