Increased risk of human parvovirus B19 infection in day-care employees: a cohort study among pregnant workers during an epidemic in Finland.

BACKGROUND: Human parvovirus B19 (B19V) infection during early pregnancy increases the risk of miscarriage. Studies have inconsistently shown an elevated risk of infection among women with occupational contacts with children. Methodological differences, particularly in defining occupational exposure and in the type of reference group, may explain the conflicting findings. METHODS: This cohort study compared B19V infections in pregnant day-care employees and healthcare professionals during a B19V epidemic in Finland. Women were identified from the files of nationwide trade unions and the National Supervisory Authority for Welfare and Health. Early-pregnancy maternal B19V IgG was analysed in 3710 women, and infections were defined as seroconversions after analysing in parallel the available umbilical cord blood samples of the 847 seronegative mothers. Independently of the serological status, the actual employment during pregnancy was assessed using registered information on employment history. RESULTS: B19V infections were more common among day-care employees (22/331, 6.6%), than among those working in healthcare (12/326, 3.7%). The adjusted HRs of B19V infection, using proportional hazard regression, was 2.63 (95% CI 1.27 to 5.46) among all women and 5.59 (95% CI 1.40 to 22.4) among nulliparous women. CONCLUSIONS: Day-care employees are at an increased risk of B19V infection, which warrants preventive measures.

Newly discovered KI, WU, and Merkel cell polyomaviruses: no evidence of mother-to-fetus transmission.

BACKGROUND: Three* human polyomaviruses have been discovered recently, KIPyV, WUPyV and MCPyV. These viruses appear to circulate ubiquitously; however, their clinical significance beyond Merkel cell carcinoma is almost completely unknown. In particular, nothing is known about their preponderance in vertical transmission. The aim of this study was to investigate the frequency of fetal infections by these viruses. We sought the three by PCR, and MCPyV also by real-time quantitative PCR (qPCR), from 535 fetal autopsy samples (heart, liver, placenta) from intrauterine fetal deaths (IUFDs) (N = 169), miscarriages (120) or induced abortions (246). We also measured the MCPyV IgG antibodies in the corresponding maternal sera (N = 462) mostly from the first trimester. RESULTS: No sample showed KIPyV or WUPyV DNA. Interestingly, one placenta was reproducibly PCR positive for MCPyV. Among the 462 corresponding pregnant women, 212 (45.9%) were MCPyV IgG seropositive. CONCLUSIONS: Our data suggest that none of the three emerging polyomaviruses often cause miscarriages or IUFDs, nor are they transmitted to fetuses. Yet, more than half the expectant mothers were susceptible to infection by the MCPyV.

Pregnancy outcomes among daycare employees in Finland.

OBJECTIVE: The aim of this study was to investigate whether working as a daycare employee increases the risk of perinatal death, pre-term birth, low birth weight, smallness for gestational age, or congenital malformations. METHODS: We conducted a register-based cohort study among daycare employees and women from various occupations of healthcare (reference group). Study subjects were identified from the files of Finnish trade unions and the National Authority for Medicolegal Affairs. Pregnancy outcomes, antenatal occupation, and working status were obtained by linkage to national registers. The final data consisted of 13 299 and 12 182 singleton births in the study and reference groups, respectively. We analyzed pregnancy outcome data using generalized estimating equations and linear regression. RESULTS: The occurrences of pre-term birth [odds ratio (OR) 0.91, 95% confidence interval (95% CI) 0.79-1.06], perinatal death (OR 0.91, 95% CI 0.62-1.34), smallness for gestational age (OR 1.01, 95% CI 0.91-1.12), and congenital malformation (OR 1.10, 95% CI 0.92-1.32) were similar among the children of the daycare employees and the reference group. The adjusted mean birth weight of the children of the daycare employees was slightly higher (14 g, 95% CI -1-29) than that of the reference group, but the difference was attenuated to 6 g in the subset of the first births. CONCLUSION: Daycare employees were not, in general, at an increased risk of an adverse pregnancy outcome. However, efforts should nevertheless be made to prevent their exposure to harmful viruses and heavy physical load during pregnancy.

Absence of human bocavirus from deceased fetuses and their mothers.

BACKGROUND: The human bocavirus (HBoV), a newly discovered parvovirus, is closely related to the bovine parvovirus and the canine minute virus, which are known to cause adverse pregnancy outcomes. Another human parvovirus, B19, can lead to fetal hydrops, miscarriage and intrauterine fetal death (IUFD). OBJECTIVES: To determine the prevalence of HBoV DNA in aborted fetuses and IUFDs. The HBoV serology of the mothers was also studied. STUDY DESIGN: We retrospectively studied all available fetuses (N=535) autopsied during 7/1992-12/1995, and 1/2003-12/2005 in Helsinki, Finland. All available formalin-fixed paraffin-embedded fetal tissues - placenta, heart and liver - of 120 miscarriages, 169 IUFDs, and 246 induced abortions were studied by quantitative PCR. We also measured the HBoV IgM and IgG antibodies in the corresponding maternal sera (N=462) mostly of the first trimester. The IgM-positive sera underwent HBoV PCR. RESULTS: None of the fetal tissues harbored HBoV DNA. A total of 97% (448/462) of the mothers were positive for IgG antibodies to HBoV, while only 0.9% (4/462) exhibited HBoV-specific IgM antibodies without viremia or respiratory symptoms. One IgM-positive mother had an unexplained fetal loss. CONCLUSIONS: We did not find HBoV DNA in any of the deceased fetuses. Almost all pregnant women were HBoV-IgG positive.

Parvovirus b19 infection in fetal deaths.

BACKGROUND: Parvovirus B19 infection during pregnancy can lead to nonimmune fetal hydrops, miscarriage, and intrauterine fetal death (IUFD). Some studies have suggested that parvovirus B19 infection may surprisingly often result in nonhydropic fetal death during the third trimester, in the absence of maternal serological evidence of acute infection. This study was conducted to investigate the prevalence of parvovirus B19 DNA among fetuses from miscarriages and IUFDs. METHODS: We retrospectively studied 535 unborn fetuses, including 120 fetuses from miscarriages and 169 from IUFDs. The control fetuses were 246 fetuses from induced abortions. All fetuses were autopsied from July 1992 through December 1995 and from January 2003 through December 2005 in Helsinki, Finland. The period included a major epidemic of parvovirus B19 infection in 1993. Formalin-fixed, paraffin-embedded fetal tissues were studied with use of a highly sensitive and specific PCR that was capable of detecting all 3 parvovirus B19 genotypes and by histologic examination. In addition, maternal parvovirus B19 serological status was determined. RESULTS: Parvovirus B19 DNA was detected in 5 fetuses with gestational ages of 14, 22, 23, 30, and 39 weeks; these included fetuses from 4 (2.4%) of the 169 IUFDs and 1 (0.8%) of the 120 miscarriages. During the epidemic year 1993, the prevalence of parvovirus B19 DNA-positive fetal deaths was 6 times the prevalence during nonepidemic years. All 5 mothers of the parvovirus B19 DNA-positive fetuses had serological signs of acute parvovirus B19 infection close to the time of fetal death. The only nonhydropic fetus was full-term. CONCLUSIONS: Our findings indicate that the prevalence of parvovirus B19 infection among fetuses from IUFDs is low. In particular, our findings did not verify the claimed high prevalence of third-trimester nonhydropic IUFDs associated with parvovirus B19.