Rubella monitoring in pregnancy as a means for evaluating a possible reemergence of rubella.

Objective: Although it is commonly accepted that rubella is well-controlled, a recent reemergence of both pertussis and measles might also predict a reemergence of rubella. This study was designed to estimate the current incidence of rubella exposure in pregnancy.

Study Design: This was a prospective, descriptive study, conducted in Houston, TX, at The Woman's Hospital of Texas. Women are typically screened for rubella immunity at the beginning of pregnancy. Rubella nonimmunity is defined as a titer less than 10 IU/mL in the US. Women who were non-immune early in pregnancy (<20 weeks) were recruited for this study and asked to be tested again for rubella immunity at the time of delivery.

Results: Of 298 women who were rubella nonimmune (IgG <10 IU/mL) early in pregnancy, 19 converted to immune status (IgG >40 IU/mL, defined as at least a 4-fold increase) at time of delivery, a rate of 6.38% (4.12% to 9.75%; 95% Wilson-Score confidence interval). For the 19 patients who converted to immune status at time of delivery, 8 patients had levels of 40-150 IU/mL, 6 patients had levels of 151-300 IU/mL, 2 patients had levels of 301-500 IU/mL, and 3 patients had levels >500 IU/mL.

Conclusion: Pregnancy is a critical time to evaluate rubella exposure. This study estimated the current incidence of rubella exposure in pregnancy to be 6.38%.