Rubella Hemagglutination Inhibition Titers

To the Editor.— We would like to illustrate the desirability of having prenatal rubella serology specimens available for retesting (1981; 245:1647). 1 Report of a Case.— On May 2, 1981, a 24-year-old woman (gravida 1, para 0, abortus 0) was seen by her obstetrician at ten weeks' gestation. At that time, the patient was found to have a rubella hemagglutination inhibition (HI) titer of less than 1:8. She had no history of a previous vaccination. Approximately eight weeks later the patient had another rubella HI determination as part of her hospital's routine employee rubella screening program. On Aug 3 the hospital-based laboratory reported back an HI titer of 1:32. The patient had no known recent exposure to rubella and had not experienced any rash. Since the patient's HI titer of 1:32 was thought to be lower than that expected after a recent rubella infection (1981; 245:1647), a third serum specimen