Reactivation of BK polyomavirus during pregnancy, vertical transmission, and clinical significance: A meta-analysis.

BACKGROUND: Studies have shown conflicting results on the prevalence and the risks of BK reactivation among pregnant women. In addition, the prevalence of vertical transmission and its clinical significance during pregnancy are not well studied.

OBJECTIVES: The study's aims were (1) to investigate the prevalence, and (2) to assess the risk of BK Polyomavirus reactivation and its clinical significance in pregnant women and fetuses.

STUDY DESIGN: A literature search was performed using MEDLINE, EMBASE and Cochrane Database from inception through May 31, 2017. We included studies that reported prevalence, relative risks, odds ratios, or hazard ratios of BK Polyomavirus reactivation during pregnancy. Pooled odds ratios (ORs) and 95% CI were calculated using a random-effect model. The protocol for this study is registered with PROSPERO (International Prospective Register of Systematic Reviews; no. CRD42017063919).

RESULTS: 17 observational studies with a total of 2553 pregnant women were enrolled. The estimated prevalence of BK seropositivity and BK in urine (viruria) among pregnant women were 79.2% (95%CI: 69.6%-86.4%) and 18.9% (95%CI: 10.4%-31.8%). When compared to non-pregnant women, the pooled ORs of BK seropositivity and BK viruria in pregnant women were 1.84 (95%CI: 1.05-3.22) and 6.02 (95%CI: 2.43-14.92), respectively. The estimated prevalence of positive BK-specific IgM antibody in cord blood was 4.9% (95%CI: 0.5%-36.2%). The data on the fetal effects of BK virus were limited. Although BK was detected in fetal organs, available data suggested no association between BK infection and adverse consequences such as miscarriage during pregnancy or childhood malignancy.

CONCLUSION: Our meta-analysis demonstrates a significantly increased risk of BK Polyomavirus reactivation during pregnancy. Although vertical transmission can occur with an overall estimated prevalence of 4.9%, there are currently no data suggesting harm to pregnant women and fetuses from BK Polyomavirus.