Changing patterns of cytomegalovirus seroprevalence among pregnant women in Norway between 1995 and 2009 examined in the Norwegian Mother and Child Cohort Study and two cohorts from Sør-Trøndelag County: a cross-sectional study

OBJECTIVES: To examine cytomegalovirus (CMV) seroprevalence and associated risk factors for CMV seropositivity in pregnant Norwegian women. DESIGN: Cross-sectional study. SETTING: The Norwegian Mother and Child Cohort Study (MoBa) in addition to two random samples of pregnant women from Sør-Trøndelag County in Norway. PARTICIPANTS: Study group 1 were 1000 pregnant women, randomly selected among 46 127 pregnancies in the MoBa (1999–2006) at 17/18 week of gestation. Non-ethnic Norwegian women were excluded. Study groups 2 (n=1013 from 1995) and 3 (n=979 from 2009) were pregnant women at 12 weeks of gestation from Sør-Trøndelag County. OUTCOME MEASURES: CMV seropositivity in blood samples from pregnant Norwegian women. RESULTS: CMV-IgG antibodies were detected in 59.9% and CMV-IgM antibodies in 1.3% of pregnant Norwegian women in study group 1. Women from North Norway demonstrated a higher CMV-IgG seroprevalence (72.1%) than women from South Norway (58.5%) (OR 1.83, 95% CI 1.17 to 2.88). The CMV-IgG seroprevalence was higher among women with low education (70.5%) compared to women with higher education (OR 2.20, 95% CI 1.24 to 3.90). Between 1995 and 2009 the CMV-IgG seroprevalence increased from 63.1% to 71.4% in pregnant women from Sør-Trøndelag County (study groups 2 and 3; p<0.001). The highest CMV-IgG seroprevalence (79.0%) was observed among the youngest pregnant women (<25 years) from Sør-Trøndelag County in 2009 (study group 3). CONCLUSIONS: The CMV-IgG seroprevalence of pregnant Norwegian women varies with geographic location and educational level. Additionally, the CMV-IgG seroprevalence appears to have increased over the last years, particularly among young pregnant women.