Dynamics of pregnancy-associated polyomavirus urinary excretion: a prospective longitudinal study

Asymptomatic polyomaviruria of pregnancy has been documented in point prevalence studies, but little attention has been given to the dynamics of polyomavirus excretion during pregnancy because of its benign course. We tested the hypothesis that the frequency and/or magnitude of polyomavirus excretion would increase as pregnancy progresses. Urine specimens were obtained prospectively from 179 healthy women during uncomplicated pregnancies and 37 healthy non-pregnant women. Real-time polymerase chain reaction was used to determine BK virus (BKV) and JC virus (JCV) viral loads in urine, blood, and rectal and vaginal swabs collected during routine obstetric and gynecologic clinic visits. Asymptomatic urinary shedding of BKV and/or JCV was observed in 384 (48.0%) of 800 specimens from 100 (55.8%) pregnant women. BKV excretion was more common in pregnant than non-pregnant women (41.3% vs. 13.5%, P = 0.0026). The frequency of JCV excretion was no different in pregnant compared to non-pregnant women. The frequency and magnitude of polyomavirus shedding did not vary with gestational age. Post-partum shedding of BKV, but not JCV, rapidly decreased to undetectable levels. Pregnancy-associated BKV excretion begins early in pregnancy and terminates rapidly post-partum. Neither the frequency nor magnitude of BKV or JCV shedding increased with pregnancy progression. Further study into the host factors that regulate pregnancy-associated BKV excretion may allow identification of the host factors that predict susceptibility to BKV-associated diseases in immune compromised patients.