Assessing Rubella Immunity: Seroprevalence among Pregnant Women in Brazzaville, Congo

Background: Rubella is a major public health problem because of its teratogenic effects, especially in early pregnancy. Understanding the serological profile of pregnant women is crucial to preventing congenital rubella syndrome. This study aimed to determine this profile in pregnant women affected by rubella. Methodology: We conducted a prospective descriptive study on blood plasmas from pregnant women over a period of three months, from January 1 to March 31, 2022. A total of 98 blood plasma samples from pregnant women were analyzed. Sampling was carried out systematically on all blood samples from pregnant women who had attended the laboratory of the Blanche Gomez Mother-Child Specialty Hospital in Brazzaville, Congo, for biological investigations. IgG and IgM assay were performed using the Architect i1000S Ranalyzer (ABBOTT), using the micro particle chemiluminescence immunological technique. Results: The overall IgG seropositivity of pregnant women was 91.8%. This rate was higher among women over 34 years of age, reaching 100%. The 16-24 and 25-34 age groups had 95.7% and 87.3% seropositivities, respectively. The distribution of the population by gestational age showed maximum seropositivity among women in the second trimester of pregnancy (97.5%), followed by those in the first trimester (88.4%) and third trimester (86.7%). Notably, 62.5% of pregnant women in the first trimester had a negative serology. Mean IgG titers were highest in women aged 25 to 34 years (94.3 IU/L) and in those in the third trimester of pregnancy (109.2 IU/L). IgG seroprevalence showed no statistically significant differences between age groups (p= 0.405) or between trimesters of pregnancy (p= 0.376). No pregnant women have been IgM positive. Conclusion: IgG seropositivity (91.8%) shows strong immunity against rubella. No pregnant women developed IgM, indicating the absence of recent infections. Vulnerability in the first quarter (62.5%) remains a concern. Surveillance, awareness-raising and vaccination are essential to improve vaccination coverage and protect vulnerable populations in Congo, thereby reducing transmission and protecting future generations.