Frequency of human parvovirus B19 infection in intrauterine fetal death

Epidemic of parvovirus B19 and disease severity in pregnant people, Denmark, January to March 2024

We report an epidemic of parvovirus B19 infections in Denmark during the first quarter of 2024, with a peak incidence 3.5 times higher than during the most recent epidemic in 2017. In total, 20.1% (130/648) of laboratory-confirmed cases were pregnant. Severe adverse outcomes were observed among 12.3% (16/130) of pregnant people and included foetal anaemia, foetal hydrops and miscarriage. Parvovirus B19 infection is not systematically monitored, but a national laboratory-based surveillance system is currently being established in Denmark.

Globoside and the mucosal pH mediate parvovirus B19 entry through the epithelial barrier

Parvovirus B19 (B19V) is transmitted primarily via the respiratory route, however, the mechanism involved remains unknown. B19V targets a restricted receptor expressed in erythroid progenitor cells in the bone marrow. However, B19V shifts the receptor under acidic conditions and targets the widely expressed globoside. The pH-dependent interaction with globoside may allow virus entry through the naturally acidic nasal mucosa. To test this hypothesis, MDCK II cells and well-differentiated human airway epithelial cell (hAEC) cultures were grown on porous membranes and used as models to study the interaction of B19V with the epithelial barrier. Globoside expression was detected in polarized MDCK II cells and the ciliated cell population of well-differentiated hAEC cultures. Under the acidic conditions of the nasal mucosa, virus attachment and transcytosis occurred without productive infection. Neither virus attachment nor transcytosis was observed under neutral pH conditions or in globoside knockout cells, demonstrating the concerted role of globoside and acidic pH in the transcellular transport of B19V. Globoside-dependent virus uptake involved VP2 and occurred by a clathrin-independent pathway that is cholesterol and dynamin-dependent. This study provides mechanistic insight into the transmission of B19V through the respiratory route and reveals novel vulnerability factors of the epithelial barrier to viruses.

Prevalence of parvovirus B19 antibodies in pregnant women in northern Benin

OBJECTIVES

Parvovirus B19 (B19V) infection in pregnancy is generally asymptomatic, but in about 3% it can cause complications, including miscarriage, severe foetal anaemia and foetal hydrops. The seroprevalence in pregnancy ranges from 20% to 82% in Africa, but there are no data for Benin. We therefore retrospectively assessed the seroprevalence of B19V in pregnant women attending the Saint Jean de Dieu Hospital in Tanguiéta, a rural district of Atacora, in northern Benin.

METHODS

We searched for anti-B19V immunoglobulin M (IgM) and immunoglobulin G (IgG) antibodies in 227 sequential sera from as many women (mean age 26.3 years, range: 16-41) of whom 30 were in the first trimester, 66 in the second and 131 in the third. Samples that tested positive for IgM were analysed with an immunoblot test and the viral genome (DNA-B19V) was searched for using a polymerase chain reaction.

RESULTS

Of the 227 women, 153 (67.4%) were positive for IgG anti-B19V, 7 (3.1%) for IgM and 73 (32.2%) were non-immune. Six IgM-positive women were also IgG positive. The difference in IgG seroprevalence between trimesters or ages was not statistically significant. Of the seven IgM-positive samples, three were confirmed positive by immunoblot (of which two were DNA-B19V positive), three were indeterminate (DNA-B19V negative) and one was negative (DNA-B19V negative). Of the three women with confirmed positive IgM, two were in the third trimester and one in the second trimester of pregnancy.

CONCLUSIONS

The seroprevalence of anti-B19V IgG among pregnant women in Benin is high and in line with those reported in some African countries. IgM seroprevalence is also similar to that described in some African countries in non-epidemic periods. The low viral load observed depicts non-acute infections, but it is difficult to establish the precise time of the infection, especially for women tested in the second or third trimester of pregnancy, when the observed viremia could be a sign of an acute infection that occurred in the previous trimester. Consequently, clinical follow-up and further investigations to highlight possible foetal consequences are indicated.

Prevalence of anti-parvovirus B19 IgG and IgM and parvovirus B19 viremia in pregnant women in an urban area of Northern Italy

Parvovirus B19 (B19V) infection in pregnancy is mostly asymptomatic, but can cause complications including abortion and fetal hydrops. Although its infection is ubiquitous, seroprevalence among pregnant women varies according to different geographical areas. Since seroprevalence data in Italy are limited, the prevalence of antibodies and DNA in pregnant women was evaluated retrospectively, correlating the clinical situation of mothers and newborns. One thousand eight hundred and ninety-three sequential sera were examined from pregnant women (60.8% in the first trimester, 16.6% in the second one, and 22.6% in the third one, respectively) for anti-B19V IgG and IgM (confirmed by immunoblot); 1402 (74.1%) were of Italian origin and 491 (25.9%) non-Italian women. Molecular tests were used to search for viral genome. One thousand three hundred and fifteen (69.5%) samples were IgG-positive, 21 (1.1%) IgM-positive, and 578 (30.5%) nonimmune. The difference in IgG seroprevalence between Italian (71.1%) and non-Italian women (64.8%) was statistically significant. Of the 21 IgM-positive women, 16 were confirmed positive also by immunoblot (prevalence: 0.8%), of which 11 were viraemic (prevalence: 0.6%; mean 1.3 × 10⁴  geq/ml). Mothers were asymptomatic, and the newborns had no clinical signs of congenital infection. IgG seroprevalence in Italy is high, with differences between Italian women and non-Italian women from geographic areas with lower endemic levels of B19V. The consistent migratory flows in place could lead to an increase in the number of susceptible women. The prevalence of viremia is low, and has not been associated with evident fetal damage at birth.

Investigation and management of stillbirth: a descriptive review of major guidelines

Stillbirth is a common and devastating pregnancy complication. The aim of this study was to review and compare the recommendations of the most recently published guidelines on the investigation and management of this adverse outcome. A descriptive review of guidelines from the American College of Obstetricians and Gynecologists (ACOG), the Royal College of Obstetricians and Gynecologists (RCOG), the Perinatal Society of Australia and New Zealand (PSANZ), the Society of Obstetricians and Gynecologists of Canada (SOGC) on stillbirth was carried out. Regarding investigation, there is consensus that medical history and postmortem examination are crucial and that determining the etiology may improve care in a subsequent pregnancy. All guidelines recommend histopathological examination of the placenta, genetic analysis and microbiology of fetal and placental tissues, offering less invasive techniques when autopsy is declined and a Kleihauer test to detect large feto-maternal hemorrhage, whereas they discourage routine screening for inherited thrombophilias. RCOG and SOGC also recommend a complete blood count, coagulopathies' testing, anti-Ro and anti-La antibodies' measurement in cases of hydrops and parental karyotyping. Discrepancies exist among the reviewed guidelines on the definition of stillbirth and the usefulness of thyroid function tests and maternal viral screening. Moreover, only ACOG and RCOG discuss the management of stillbirth. They agree that, in the absence of coagulopathies, expectant management should be considered and encourage vaginal birth, but they suggest different labor induction protocols and different management in subsequent pregnancies. It is important to develop consistent international practice protocols, in order to allow effective determination of the underlying causes and optimal management of stillbirths, while identifying the gaps in the current literature may highlight the need for future research.

Parvovirus B19 Intrauterine Infection and Eventration of the Diaphragm

Parvovirus B19 infection in pregnancy may have a poor outcome for the fetus. Ocular anomalies, brain damage with hydrocephalus and central nervous system (CNS) scarring, cleft lip and hypospadias, as well myocarditis and congenital heart disease have been reported. We present a case of a preterm female neonate born with ascites, hydrothorax and congenital diaphragmatic eventration (CDE), with a prenatal diagnosis of congenital diaphragmatic hernia (CDH). The neonate was born prematurely at 32 weeks gestation with caesarean section due to a previous caesarean delivery. She was immediately intubated in the delivery room, transferred in the Neonatal Intensive Care Unit (NICU) and supported with high frequency oscillatory ventilation (HFOV). The diagnosis of CDH was sonographically estimated from the 20th week of gestation and surgical correction was decided. During surgery CDE was diagnosed instead of CDH and despite postoperatively care the neonate developed disseminated intravascular coagulation and finally died in the 40th hour of life. Along with the identification of parvovirus B19 in the pleural fluid by PCR, the biopsy of the diaphragm revealed connective tissue, full of vasculature and absence muscle tissue. Although only cytomegalovirus, rubella, and toxoplasmosis were considered to be associated with CDE, parvovirus B19 might also be related to this congenital diaphragmatic malformation. In CDE, the function of the lungs can be compromised as a consequence of the compression applied by the abdominal organs. The neonatologists should include this condition in their differential diagnosis for a more direct and effective management.

Fusion of parvovirus B19 receptor-binding domain and pneumococcal surface protein A induces protective immunity against parvovirus B19 and Streptococcus pneumoniae

BACKGROUND

Parvovirus B19 (B19) is a well-known cause of fifth disease in children, but infection during pregnancy may cause hydrops fetalis and stillbirth. The receptor-binding domain (RBD) of the VP1 unique capsid plays a pivotal role in infection. Here, we aimed to improve the immunogenicity of an RBD-based vaccine by genetically fusing it with Streptococcus pneumoniae surface protein A (PspA).

METHODS

Mice were intramuscularly injected with RBD-based vaccines. Antigen-specific antibodies and neutralizing activity against B19 were measured. Protective immunity against S. pneumoniae was evaluated by monitoring the survival of mice nasally challenged with bacteria and determining antigen-specific T cell activation in splenic cells.

RESULTS

RBD alone failed to generate neutralizing antibodies against B19, but fusion with PspA induced higher levels of neutralizing IgG compared to B19 virus-like particles. Furthermore, a comparable level of PspA-specific IgG was induced by RBD-PspA and PspA alone, which was sufficient to protect mice against pneumococcal infection. Stimulation with PspA, but not RBD, induced cytokine production in splenic cells from mice immunized with RBD-PspA, suggesting that PspA-specific T cells supported immunoglobulin class switching of both RBD- and PspA-specific B cells.

CONCLUSIONS

RBD-PspA should be an effective bivalent vaccine against B19 and S. pneumoniae infections.

Enhanced Cell-Based Detection of Parvovirus B19V Infectious Units According to Cell Cycle Status

Human parvovirus B19 (B19V) causes various human diseases, ranging from childhood benign infection to arthropathies, severe anemia and fetal hydrops, depending on the health state and hematological status of the patient. To counteract B19V blood-borne contamination, evaluation of B19 DNA in plasma pools and viral inactivation/removal steps are performed, but nucleic acid testing does not correctly reflect B19V infectivity. There is currently no appropriate cellular model for detection of infectious units of B19V. We describe here an improved cell-based method for detecting B19V infectious units by evaluating its host transcription. We evaluated the ability of various cell lines to support B19V infection. Of all tested, UT7/Epo cell line, UT7/Epo-STI, showed the greatest sensitivity to B19 infection combined with ease of performance. We generated stable clones by limiting dilution on the UT7/Epo-STI cell line with graduated permissiveness for B19V and demonstrated a direct correlation between infectivity and S/G2/M cell cycle stage. Two of the clones tested, B12 and E2, reached sensitivity levels higher than those of UT7/Epo-S1 and CD36⁺ erythroid progenitor cells. These findings highlight the importance of cell cycle status for sensitivity to B19V, and we propose a promising new straightforward cell-based method for quantifying B19V infectious units.

Mechanisms and evidence of vertical transmission of infections in pregnancy including SARS-CoV-2s

There remain unanswered questions concerning mother‐to‐child‐transmission of SARS‐CoV‐2. Despite reports of neonatal COVID‐19, SARS‐CoV‐2 has not been consistently isolated in perinatal samples, thus definitive proof of transplacental infection is still lacking. To address these questions, we assessed investigative tools used to confirm maternal‐fetal infection and known protective mechanisms of the placental barrier that prevent transplacental pathogen migration. Forty studies of COVID‐19 pregnancies reviewed suggest a lack of consensus on diagnostic strategy for congenital infection. Although real‐time polymerase chain reaction of neonatal swabs was universally performed, a wide range of clinical samples was screened including vaginal secretions (22.5%), amniotic fluid (35%), breast milk (22.5%) and umbilical cord blood. Neonatal COVID‐19 was reported in eight studies, two of which were based on the detection of SARS‐CoV‐2 IgM in neonatal blood. Histological examination demonstrated sparse viral particles, vascular malperfusion and inflammation in the placenta from pregnant women with COVID‐19. The paucity of placental co‐expression of ACE‐2 and TMPRSS2, two receptors involved in cytoplasmic entry of SARS‐CoV‐2, may explain its relative insensitivity to transplacental infection. Viral interactions may utilise membrane receptors other than ACE‐2 thus, tissue susceptibility may be broader than currently known. Further spatial‐temporal studies are needed to determine the true potential for transplacental migration.

Identification and management of congenital parvovirus B19 infection

Parvovirus B19 (B19V) infection is well known for its mild, self-limiting clinical presentations in children, such as erythema infectiosum. Approximately 40% of women of childbearing age are susceptible to B19V infection. While maternal B19V infection usually has a good prognosis, B19V can cause severe fetal anaemia and pregnancy loss due to its ability to suppress erythroid progenitor cells. Non-invasive ultrasound monitoring for fetal anaemia is usually performed if maternal seroconversion occurs in the first 20 weeks of gestation, with amniocentesis for fetal infection reserved for those who first present with fetal anaemia or hydrops of unknown cause. Intrauterine transfusion is the standard treatment for severe fetal anaemia and is associated with a significant improvement in survival. However, survivors of hydrops fetalis may have a higher rate of long-term neurodevelopmental complications compared with non-hydropic survivors. This review aims to synthesise published data on the diagnosis, surveillance and outcomes of congenital parvovirus infection to assist clinicians in diagnosing and managing this important condition.

Microsphere-Based IgM and IgG Avidity Assays for Human Parvovirus B19, Human Cytomegalovirus, and Toxoplasma gondii

Human parvovirus B19, human cytomegalovirus, and Toxoplasma gondii are ubiquitous pathogens. Their infections are often asymptomatic or mild in the general population yet may be transmitted from mother to fetus during pregnancy. Maternal infections by these pathogens can cause severe complications to the fetus or congenital abnormalities. As a rule, the risk of maternal transmission is critically related to the infection time; hence, it is important to determine when a pregnant woman has acquired the infection. In this study, we developed new diagnostic approaches for the timing of infections by three pathogens. All the new assays appeared to be highly sensitive and specific, providing powerful tools for medical diagnosis.

Human parvovirus B19 (here B19), human cytomegalovirus (HCMV), and Toxoplasma gondii infections during pregnancy can lead to severe complications. While traditional diagnosis of infections is mostly confined to one pathogen at a time, a multiplex array is a feasible alternative to improve diagnostic management and cost-efficiency. In the present study, for these three pathogens, we developed microsphere-based suspension immunoassays (SIAs) in multiplex and monoplex formats for the detection of antimicrobial IgM antibodies as well as corresponding chaotrope-based IgG avidity SIAs. We determined the diagnostic performances of the SIAs versus in-house and commercial reference assays using a panel of 318 serum samples from well-characterized clinical cohorts. All the newly developed assays exhibited excellent performance compared to the corresponding high-quality reference methods. The positive and negative percent agreements of the IgM SIAs in comparison with reference methods were 95 to 100% and 98 to 100%, and those of the IgG avidity SIAs were 92 to 100% and 95 to 100%, respectively. Kappa efficiency values between the SIAs and the corresponding reference assays were 0.91 to 1. Furthermore, with another panel comprising 391 clinical samples from individuals with primary infection by B19, HCMV, or T. gondii, the IgM SIAs were highly sensitive for the detection of acute infections, and the IgG avidity SIAs were highly specific for the separation of primary infections from past immunity. Altogether, the strategy of IgM multiplex screening followed by IgG avidity reflex testing can provide high-throughput and accurate means for the detection and stage determination of B19, HCMV, and T. gondii infections.

IMPORTANCE Human parvovirus B19, human cytomegalovirus, and Toxoplasma gondii are ubiquitous pathogens. Their infections are often asymptomatic or mild in the general population yet may be transmitted from mother to fetus during pregnancy. Maternal infections by these pathogens can cause severe complications to the fetus or congenital abnormalities. As a rule, the risk of maternal transmission is critically related to the infection time; hence, it is important to determine when a pregnant woman has acquired the infection. In this study, we developed new diagnostic approaches for the timing of infections by three pathogens. All the new assays appeared to be highly sensitive and specific, providing powerful tools for medical diagnosis.

Parvovirus B19 DNAemia in pregnant women in relation to perinatal death: A nested case-control study within a large population-based pregnancy cohort

INTRODUCTION

Parvovirus B19 (B19V) is the infectious cause of exanthema infectiosum. In Europe around 40% of pregnant women are susceptible to infection. Having small children at home is the main risk factor for contracting an infection during pregnancy. The association between B19V-infection and perinatal death is not yet settled. The aims of the study were to estimate the association between maternal parvovirus B19 infection in pregnancy and perinatal death, and to assess the significance of a positive B19V PCR in pregnancy.

MATERIAL AND METHODS

The study population consists of women included in the Norwegian Mother and Child Cohort Study, a prospective population-based pregnancy cohort of nearly 100 000 women. Blood samples were obtained during weeks 17-18 in pregnancy (M1), at birth, and in umbilical cord blood. Within participants in the pregnancy cohort, 138 cases of perinatal death and 1350 controls with live-born children were included in a nested case-control study. Samples were analyzed with B19V serology and B19V PCR according to a predefined test algorithm. For cases, medical records and laboratory results from hospitals were combined with the results of B19V serology and PCR. The reported causes of perinatal death were categorized using the classification system: Causes Of Death and Associated Conditions (CODAC).

RESULTS

The B19V seroconversion rates were 9.8% for cases and 6.8% for control mothers. The odds ratio for maternal B19V infection in cases compared with controls was 1.28 (95% CI 0.35-4.70), adjusted for age, parity, body mass index and tobacco use. B19V-PCR-positive samples were detected at weeks 17-18 of gestation in both cases and controls. The proportion of positive samples was similar in cases and controls, 24% and 28.2%, respectively. Mothers with PCR-positive M1 samples transmitted B19V vertically in 9.1% of cases and in 11.9% of the controls. Of all perinatal deaths, 53% were attributed to placental pathology or unknown causes.

CONCLUSIONS

B19V PCR positivity was high and similar in both cases and controls. In our study B19V DNAemia was not seen to be associated with fatal outcome of pregnancy. The clinical significance of B19V DNA detection during pregnancy is uncertain. Caution is needed when diagnosing a B19V infection based only on B19V DNAemia.

Antibodies against human parvovirus B19 in pregnant women in Ogbomoso, Oyo State Nigeria

Infection caused by Human parvovirus B19 (HPVB19) during pregnancy has been associated with adverse effects on fetus such as intrauterine fetal death but there is dearth information about the seroprevalence and risk factors among pregnant women. This study was carried out to determine the incidence of specific IgM antibodies to HPVB19 among pregnant women attending Bowen University Teaching Hospital, Ogbomoso, Oyo State. A total of 185 participants, in the age range 18-49 years, who consented voluntarily after thorough explanation of the purpose of the study were recruited for the study. Specific IgM antibodies were detected using commercially available third-generation ELISA kits. Data on socio-demographic characteristics and potential risk factors were collected using structured questionnaires. Chi-square (χ²) test was utilized to assess the association between the socio-demographic variables and HPVB19 status (P ˂ 0.05). Logistic regression was done to determine the strength of association between the potential risk factors and HPVB19 status (P ˂ 0.05). The overall incidence of IgM antibody recorded was 2.70% (5/185). Pregnant women in the age group 36-45 (7.7%) years had the highest record. None of the socio-demographic characteristics and risk factor considered were significantly associated with acquiring HPVB19. However, a one-fold risk was observed among those who had previous history of blood transfusion (95% CI = 0.949-0.997, OR = 1.0) The findings in this study confirmed the presence of antibodies to HPVB19 among pregnant women in Ogbomoso. Public awareness, enlightenment, and screening for the virus should be encouraged to prevent fetal complications during pregnancy.

Parvovirus B19 infection during pregnancy and risks to the fetus

Parvovirus B19 infects 1 to 5% of pregnant women, generally with normal pregnancy outcomes. During epidemics, the rate of infection is higher. Major congenital anomalies among offspring of infected mothers are rare, as the virus does not appear to be a significant teratogen. However, parvovirus B19 infection may cause significant fetal damage, and in rare cases, brain anomalies and neurodevelopmental insults, especially if infection occurs in the first 20 weeks of pregnancy. Parvovirus B19 is also an important cause of fetal loss, especially in the second half of pregnancy when spontaneous fetal loss from other causes is relatively rare. Parvovirus B19 infection may affect many fetal organs and can cause severe anemia, following fetal erythroid progenitor cells infection and apoptosis, especially in fetuses, that have shortened half-life of erythrocytes. Severe anemia may cause high output cardiac failure and nonimmune hydrops fetalis. In addition, parvovirus B19 may directly infect myocardial cells and produce myocarditis that further aggravates the cardiac failure. Intrauterine fetal transfusion is commonly used for the treatment of severe fetal anemia with survival rates of 75 to 90% and significant reduction of fetal morbidity. Only 66 cases were evaluated neurodevelopmentally, of which 10 (16%) had slight or severe neurodevelopmental problems. Because parvovirus B19 infection can cause severe fetal morbidity and mortality, it should be part of the routine work-up of pregnant women who have been exposed to the virus or of pregnancies with suspected fetal hydrops. Assessment for maternal infection during pregnancy is especially important during epidemics, when sero-conversion rates are high. Birth Defects Research 109:311-323, 2017. © 2017 Wiley Periodicals, Inc.

Parvovirus B19 infection in pregnancy-awareness and opportunities

Parvovirus B19 (B19V) is a human pathogenic virus associated with a wide range of clinical conditions. In pregnancy, B19V poses a potential hazard to the fetus as crossing the placental barrier and infecting erythroid progenitor cells in bone marrow and liver, it blocks fetal erythropoiesis leading to profound anemia, hydrops and/or fetal death. The virus is not regarded as a teratogen, however more scientific awareness is emerging on mechanisms and consequences of intrauterine infection and possible sequelae in the neonatal development. Reliable diagnostic procedures and fetal management strategies, including intrauterine transfusion, are established. In spite of being a recognized fetotropic agent possibly leading to fetal loss, testing for B19V is not routinely included in preconception or antenatal screenings, possibly delaying the management of B19V-complicated pregnancies. Continuous advances in B19V research will provide for better diagnostic methods and algorithms, as well as for the development of effective prophylactic interventions and novel therapeutic options.

The Role of Infection and Inflammation in Stillbirths: Parallels with SIDS?

It has been suggested that stillbirths are part of the spectrum of infant deaths that includes sudden infant death syndrome (SIDS). This paper examines the hypothesis that risk factors associated with stillbirths might contribute to dysregulation of inflammatory responses to infections that could trigger the physiological responses leading to fetal loss. These include genetic factors (ethnic group, sex), environmental (infection, cigarette smoke, obesity), and developmental (testosterone levels) factors. Interactions between the genetic, environmental, and developmental risk factors are also considered, e.g., the excess of male stillborn infants in relation to the effects of testosterone levels during development on pro-inflammatory responses. In contrast to SIDS, inflammatory responses of both mother and fetus need to be considered. Approaches for examining the hypothesis are proposed.

Clinical features of 10 fetuses with prenatally diagnosed parvovirus b19 infection and fetal hydrops

OBJECTIVES

To evaluate the clinical features of fetuses with prenatally diagnosed parvovirus B19 infection and fetal hydrops.

METHODS

Parvovirus infection was diagnosed by PCR analysis of amniotic fluid or fetal blood. Fetal anemia was assessed by Doppler measurements of the middle cerebral artery peak systolic velocity (MCA-PSV) and confirmed by fetal blood. Intrauterine transfusions (IUT) were performed only if the MCA-PSV was > 1.5°MoM.

RESULTS

In our study population 10 cases of parvovirus infection which were associated with fetal hydrops were reviewed. The median gestational age at diagnosis was 21 (16.3-24.2) weeks. Five of our cases received IUT and four fetuses survived. The remaining five cases were managed conservatively and two fetuses survived.

CONCLUSIONS

The survival rate for parvovirus infection associated with fetal hydrops was 60%. MCA-PSV and IUT are useful for the management and treatment of fetal anemia due to parvovirus infection.

Quantitative analysis of human parvovirus B19 DNA in maternal and fetal serum, and amniotic fluid during an early stage of pregnancy

Simple and accurate diagnosis of vertical transmission of human parvovirus B19 (B19V) infection remains an important issue in pregnancy. There are few reports on quantitative analysis of B19V in amniotic fluids. Quantitative estimation of B19V DNA in amniotic fluids was comparerd with those in maternal or fetal serum obtained at an early stage of pregnancy with possible mother-to-fetus transmission. All pregnant women contracted B19V infection between 13 to 14 weeks gestation. The B19V DNA amount in 3 maternal serum and amniotic fluid sample pairs collected between 16 to 27 weeks gestation was quantified by a real-time polymerase chain reaction assay. Serum from 2 fetuses was included. The B19V DNA concentrations in maternal sera and amniotic fluids ranged from 10(4) to 10(5) copies/ml and from 10(7) to 10(8) copies/ml, respectively. The B19V DNA in the amniotic fluids concentration coincided with those of each fetal serum. The concentrations in amniotic fluids are 100 to 5,000 times higher than in those of maternal sera, and corresponded to the matching fetal serum. Amniotic fluids may substitute for the fetal sera in terms of quantitative estimation of fetal B19V infection at an early stage of pregnancy.

Parvovirus infection: an immunohistochemical study using fetal and placental tissue

Parvovirus B19 infection causes 5% to 15% of cases of nonimmune hydrops fetalis. The aim of our study was to evaluate the use of immunohistochemistry in diagnosing parvovirus infection in fetal and placental tissue during routine fetal and perinatal autopsies. Histology slides of 20 cases of confirmed parvovirus infection were reviewed, and immunohistochemistry was applied to selected blocks of fetal and placental tissue. Immunohistochemistry was positive in all 20 cases, and histologic viral inclusions were seen in 19 cases. Immunohistochemical staining was closely correlated with histology and was more sensitive than histology in detecting virally infected cells, especially in autolyzed tissue. All cases also had confirmatory evidence of parvovirus infection by polymerase chain reaction of fetal liver and positive maternal serology, where it was available. We conclude that parvovirus immunohistochemistry is a reliable method for diagnosing parvovirus infection, especially in autolyzed tissue where histologic assessment may be suboptimal.

Intrauterine infection with parvovirus B19 and CMV: implications in early and late gestation fetal demise

In utero viral infections have been associated with an adverse pregnancy outcome and may have a causative role in the unexplained fetal death file. Parvovirus B19 and cytomegalovirus are among the most common pathogens implicated in fetal loss cases. Parvovirus B19 has been reported to account for cases of spontaneous abortions, intrauterine fetal death and nonimmune hydrops fetalis, whereas cytomegalovirus accounts for nonimmune hydrops fetalis, intrauterine growth retardation and congenital anomalies. This review aims to summarize the current literature in an attempt to underline the need for routine screening, close follow-up and prevention. A better understanding of the pathogenetic mechanisms of viral infections during the crucial time of organogenesis, along with early detection, may contribute to the reduction in stillbirth rate.

Viral infections: contributions to late fetal death, stillbirth, and infant death

OBJECTIVE

To determine the role of viral infections in causing fetal and infant death.

STUDY DESIGN

We assessed a well-validated population database of fetal (≥20 weeks gestation) and infant death for infective deaths and deaths from viruses over a 21-year period (1988-2008). We analyzed by specific viral cause, timing (late fetal loss [20-23 weeks], stillbirth [≥24 weeks], neonatal death [0-27 days], and post-neonatal infant death [28-364 days]) and across time.

RESULTS

Of the 989 total infective deaths, 108 were attributable to viral causes (6.5% of late fetal losses, 14.5% of stillbirths, 6.5% of neonatal deaths, and 19.4% of postneonatal infant deaths). Global loss (combined fetal and infant losses per 100,000 registerable births) was 139.6 (95% CI, 130.9-148.3) for any infective cause and 15.2 (95% CI, 12.3-18.1) for viral infections. More than one-third (37%) of viral-attributed deaths were before live birth, from parvovirus (63%) or cytomegalovirus (33%). Parvovirus accounted for 26% (28 of 108) of all viral deaths. Cytomegalovirus was associated with a global loss rate of 3.1 (95% CI, 1.8-4.4) and an infant mortality rate of 1.3 (95% CI, 0.4-2.1) per 100,000 live births; 91% of cases were congenital infections. Herpes simplex virus caused death only after live births (infant mortality rate, 1.4; 95% CI, 0.5-2.3). No changes in rates were seen over time.

CONCLUSION

We have identified a substantial contribution of viral infections to global fetal and infant losses. More than one-third of these losses occurred before live births. Considering our methodology, our estimates represent the minimum contribution of viral illness. Strategies to reduce this burden are needed.

Parvovirus B19 Achievements and Challenges

Parvovirus B19 is a widespread human pathogenic virus, member of the Erythrovirus genus in the Parvoviridae family. Infection can be associated with an ample range of pathologies and clinical manifestations, whose characteristics and outcomes depend on the interplay between the pathogenetic potential of the virus, its adaptation to different cellular environments, and the physiological and immune status of the infected individuals. The scope of this review is the advances in knowledge on the biological characteristics of the virus and of virus-host relationships; in particular, the interactions of the virus with different cellular environments in terms of tropism and ability to achieve a productive replicative cycle, or, on the contrary, to establish persistence; the consequences of infection in terms of interference with the cell physiology; the process of recognition of the virus by the innate or adaptive immune system, hence the role of the immune system in controlling the infection or in the development of clinical manifestations. Linked to these issues is the continuous effort to develop better diagnostic algorithms and methods and the need for development of prophylactic and therapeutic options for B19V infections.

Diagnosis of in utero Parvovirus B19 infection and maternal immune response - the relevance of linear epitopes and advanced serologic testing

IMPORTANCE OF THE FIELD

Parvovirus B19 (B19V) infection in utero causing fetal anemia and non-immune hydrops fetalis (NIHF) is a potentially life-threatening event for the fetus. Postexpositional non-invasive diagnosis is based on maternal IgG/IgM response and detection of viral genome in maternal blood. Serologic testing directs prenatal follow-up. Fetal infection is confirmed by polymerase chain reaction or in situ hybridization in fetal blood and/or amniotic fluid cells. The performance of serologic tests is significant in order to direct pre- and perinatal care at rational use of resources. Timing of diagnostic procedures and knowledge of the time course of infection in pregnant, asymptomatic women are critical. IgM negative testing in the presence of prolonged viremia may complicate individual risk analysis in pregnancy. Recently, advanced IgG avidity assays and epitope-type specific assays (IgG ETS EIA) have been re-evaluated.

AREAS COVERED IN THIS REVIEW

Epidemiology, clinical relevance and management of B19V infection in pregnancy. A review of the current literature (November 1984 - May 2009) and evaluation of current information on performance and predictive value of molecular and VP1/VP2 antigen-based IgG tests directed at the diagnosis of materno-fetal B19V infection and detection of past immunity. New aspects of B19V-associated fetal disease other than anemia/NIHF are also covered.

WHAT THE READER WILL GAIN

An overview of immunology and clinical relevance of B19V infection in pregnancy, of the potential value of advanced serologic testing and fields of future research.

TAKE HOME MESSAGE

In the absence of a commercially available vaccine, serologic tests remain important tools in individual risk analysis of pregnant women exposed to B19V. Sequential application of IgG avidity and IgG ETS EIAs may improve risk stratification and timing of invasive testing in B19V-exposed pregnancies, in particular with IgM-negativity and/or persistent DNAemia. Prospective evaluation of these test systems correlated to fetal outcome in order to reduce fetal morbidity and mortality as well as the overall burden of disease of B19V with regard to fetal malformation may be subject to future research.

Parvovirus B19 in pregnancy: possible consequences of vertical transmission

OBJECTIVE

The aim was to determine the outcome of pregnancies complicated by maternal Parvovirus B19 (B19) infection.

METHOD

Among 175 pregnant women referred to our clinic because of suspicion of a B19 infection, 63 with confirmed laboratory diagnosis of acute/recent B19 infection were followed up by ultrasound and Doppler measurement of the middle cerebral artery peak systolic velocity.

RESULTS

The vertical transmission rate was 31.7% (20/63). Of the 20 infected, 8 had hydrops, 1 had signs suggestive of meconium peritonitis and 1 had an isolated hydrothorax. Three fetuses presenting with hydrops were treated with intrauterine blood transfusion. Two of them died while the last showed resolution of anemia. Among the five untreated hydropic fetuses, one presented with mild signs that resolved spontaneously, two died at 16 and 17 weeks of gestation and two had also cardiomegaly and the parents opted for elective termination of pregnancy. All the anemic fetuses had middle cerebral artery peak systolic velocity values more than 1.8 multiples of the median. No stillbirth occurred.

CONCLUSIONS

The outcome of uncomplicated cases with B19 infection is good. In the presence of hydrops prognosis was very poor. It seems therefore logical to attempt to pick up this ominous signs early.

Cytomegalovirus and Epstein-Barr virus may be associated with some cases of cerebral palsy

OBJECTIVE

Intrauterine infection is a risk factor for cerebral palsy. Previous work reported a high frequency of viral DNA in newborn screening cards from cerebral palsy cases and controls possibly due to contamination.

METHODS

Retrospective case-control study using improved methodologies to minimize contamination during PCR-based detection of viral DNA sequences. Newborn screening cards of 339 Caucasian children with cerebral palsy and 594 controls were examined. Viruses tested were herpes simplex viruses 1 and 2 (HSV1 and 2), varicella zoster virus (VZV), Epstein-Barr virus (EBV), cytomegalovirus (CMV), human herpes viruses 6, 7 and 8 (HHV6, HHV7 and HHV8), and parvovirus B19. Genotyping was performed on DNA extracted from dried blood spots.

RESULTS

CMV and EBV were detected in 5 (1.5%) and 3 (0.9%) of 339 cases, respectively, but not in controls (p = 0.047 and 0.006). Frequencies of detection of the other viruses examined were similar for cases and controls. DNA from at least one of the nine viruses tested was found in 4.4% of cases and 3.1% of controls [OR 1.4 95% CI (0.71-2.76)].

CONCLUSION

Evidence of congenital viral infection was uncommon in cases of cerebral palsy and controls. However, CMV and EBV were significantly associated with cerebral palsy.

Diagnosis, management and possibilities to prevent parvovirus B19 infection in pregnancy

Human parvovirus B19 (B19V) infection in pregnancy can cause severe fetal anemia and nonimmune hydrops fetalis, which may be associated with spontaneous abortion and fetal death. Approximately 30–40% of women of child-bearing age are not immune to B19V infection. The risk to fetal life is particularly high if maternal infection occurs during the first 20 weeks of gestation. In this article we intend to give an overview on the molecular biology, epidemiology and management of B19V infection during pregnancy. These data will be combined with an assessment of the clinical situation of the infected fetus and the possibilities for avoiding and/or preventing B19V infection in pregnant women. Currently B19V infection is the causative agent of one of the most frequently occurring infectious complications in pregnancy that endangers fetal life, and so the necessity to develop a preventive vaccine is discussed.

Gestational and fetal outcomes in B19 maternal infection: a problem of diagnosis

Parvovirus B19 infection during pregnancy is a potential hazard to the fetus because of the virus' ability to infect fetal erythroid precursor cells and fetal tissues. Fetal complications range from transitory fetal anemia and nonimmune fetal hydrops to miscarriage and intrauterine fetal death. In the present study, 72 pregnancies complicated by parvovirus B19 infection were followed up: fetal and neonatal specimens were investigated by serological and/or virological assays to detect fetal/congenital infection, and fetuses and neonates were clinically evaluated to monitor pregnancy outcomes following maternal infection. Analysis of serological and virological maternal B19 markers of infection demonstrated that neither B19 IgM nor B19 DNA detected all maternal infections. IgM serology correctly diagnosed 94.1% of the B19 infections, while DNA testing correctly diagnosed 96.3%. The maximum sensitivity was achieved with the combined detection of both parameters. B19 vertical transmission was observed in 39% of the pregnancies, with an overall 10.2% rate of fetal deaths. The highest rates of congenital infections and B19-related fatal outcomes were observed when maternal infections occurred by the gestational week 20. B19 fetal hydrops occurred in 11.9% of the fetuses, and 28.6% resolved the hydrops with a normal neurodevelopment outcome at 1- to 5-year follow-up. In conclusion, maternal screening based on the concurrent analysis of B19 IgM and DNA should be encouraged to reliably diagnose maternal B19 infection and correctly manage pregnancies at risk.

Interleukin 10 deficiency exacerbates toll-like receptor 3-induced preeclampsia-like symptoms in mice

Preeclampsia may result from overactivation of the maternal immune system and is characterized by endothelial dysfunction and excessive inflammation. Given the importance of maternal immune system regulation and anti-inflammatory cytokines in normotensive pregnancies, we hypothesized that maternal immune system activation via Toll-like receptor 3 during pregnancy would cause preeclampsia-like symptoms in mice, which would be made worse by deficiency of the anti-inflammatory cytokine interleukin 10. The Toll-like receptor 3 agonist polyinosine-polycytidylic acid (poly I:C) caused hypertension, endothelial dysfunction, and proteinuria in mice only when pregnant. In the absence of poly I:C, pregnant interleukin 10 knockout mice exhibited a significant increase in systolic blood pressure, endothelial dysfunction, and serum proinflammatory cytokines, as well as aortic and placental platelet-endothelial cell adhesion molecule expression compared with pregnant wild-type mice. Deficiency of interleukin 10 further augmented these measures in poly I:C-treated pregnant mice. In addition, sera from poly I:C-treated pregnant wild-type mice significantly decreased relaxation responses and increased platelet-endothelial cell adhesion molecule expression in isolated aortas from nonpregnant wild-type mice, and these effects were augmented by sera from poly I:C-treated interleukin 10 knockout mice. Coincubation with recombinant interleukin 10 normalized relaxation responses and platelet-endothelial cell adhesion molecule expression in all of the groups. Collectively, Toll-like receptor 3 activation during pregnancy causes preeclampsia-like symptoms, which are exacerbated by the absence of interleukin 10. Exogenous interleukin 10 treatment had beneficial effects on endothelial function and may be beneficial in women with preeclampsia.

Viral detection in hydrops fetalis, spontaneous abortion, and unexplained fetal death in utero

This study was undertaken to investigate the occurrence of viral infection in fetal death by examining tissues for the presence of DNA of several viral agents. Tissue specimens including heart, kidney, liver, lung, and placenta of 73 cases of fetal death were examined with 27 cases of elective termination of pregnancy as a control group. DNA extracted from these samples was tested for the presence of HSV, CMV, EBV, VZV, HHV-6, HHV-7, and PVB19. Viral DNA was found in one or more tissue samples from 25/73 cases (34%): CMV in 20, HSV in 5, parvovirus B19 in 5, HHV-7 in 3, and HHV-6 in 2. The presence of HHV-6 in fetal tissue has been reported rarely. No study so far has reported the detection of HHV-7 in fetal tissues with normal or adverse outcomes. Viral DNA was not found in any of the termination of pregnancy samples. Among the positive cases, eight had dual infection. One further case was positive for three viruses: HSV, CMV, and HHV-7. HHV-6 was the sole infectious agent in two cases, HHV-7 in one case, PVB19 in three, and CMV in ten cases. The finding of multiple viral DNA in 12% of the cases suggests the involvement of complex risk factors in cases of fetal loss. Although the cause of fetal death often includes other factors (e.g., chromosomal abnormalities) these data suggest the incidence of viral infective etiology may be higher than considered previously. However, larger studies are required to establish this link.

Parvovirus B19 infection in human pregnancy

Human parvovirus B19 infection is widespread. Approximately 30-50% of pregnant women are nonimmune, and vertical transmission is common following maternal infection in pregnancy. Fetal infection may be associated with a normal outcome, but fetal death may also occur without ultrasound evidence of infectious sequelae. B19 infection should be considered in any case of nonimmune hydrops. Diagnosis is mainly through serology and polymerase chain reaction. Surveillance requires sequential ultrasound and Doppler screening for signs of fetal anaemia, heart failure and hydrops. Immunoglobulins, antiviral and vaccination are not yet available, but intrauterine transfusion in selected cases can be life saving.

Model structure analysis to estimate basic immunological processes and maternal risk for parvovirus B19

After a steep monotone rise with age, the seroprevalence profiles for human parvovirus B19 (PVB19) display a decrease or plateau between the ages of 20 and 40, in each of 5 European countries. We investigate whether this phenomenon is induced by waning antibodies for PVB19 and, if this is the case, whether secondary infections are plausible, or whether boosting may occur. Several immunological scenarios are tested for PVB19 by fitting different compartmental dynamic transmission models to serological data using data on social contact patterns. The social contact approach has already been shown informative to estimate transmission rates and the basic reproduction number for infections transmitted predominantly through nonsexual social contacts. Our results show that for 4 countries, model selection criteria favor the scenarios allowing for waning immunity at an age-specific rate over the assumption of lifelong immunity, assuming that the transmission rates are directly proportional to the contact rates. Different views on the evolution of the immune response to PVB19 infection lead to altered estimates of the age-specific force of infection and the basic reproduction number. The scenarios which allow for multiple infections during one lifetime predict a higher frequency of PVB19 infection in pregnant women and of associated fetal deaths. When prevaccination serological data are available, the framework developed in this paper could prove worthwhile to investigate these different scenarios for other infections as well, such as cytomegalovirus.

Risk of fetal hydrops and non-hydropic late intrauterine fetal death after gestational parvovirus B19 infection

BACKGROUND

Risk assessment of parvovirus B19 (B19)-associated fetal complications following gestational B19 infection remains controversial.

OBJECTIVES

To determine the risk of fetal hydrops or non-hydropic late intrauterine fetal death following acute maternal B19 infection at defined gestational weeks.

STUDY DESIGN

Observational cohort study of pregnant women with serologic evidence of acute B19 infection. If available, fetal or neonatal tissue samples from cases complicated by fetal loss or hydrops were investigated for the presence of B19 DNA by polymerase chain reaction (PCR) and/or in situ hybridization (ISH).

RESULTS

Of 236 women with known pregnancy outcome, 228 had a live birth and 8 a fetal loss. The observed rate of fetal hydrops for all pregnant women was 4.2% (10/236) (95% confidence interval [CI], 2.1-7.7) and 10.6% (10/94) (95% CI, 5.2-18.7) for those infected between 9 and 20 weeks gestation. Tissue samples from 8 hydrops cases were investigated by PCR or ISH and all were B19 DNA positive. Fetal death occurring during or after gestational week 22 was only observed in one case which was associated with B19-derived fetal hydrops.

CONCLUSIONS

Our findings demonstrate that although adverse fetal outcome is a rare complication of gestational B19 infection, a relevant risk of fetal hydrops exists particularly for women infected between 9 and 20 weeks' gestation. Cases of B19-derived non-hydropic late intrauterine fetal death were not observed in the present study.

Infection-related stillbirths

Infection is an important cause of stillbirths worldwide: in low-income and middle-income countries, 50% of stillbirths or more are probably caused by infection. By contrast, in high-income countries only 10-25% of stillbirths are caused by infection. Syphilis, where prevalent, causes most infectious stillbirths, and is the infection most amenable to screening and treatment. Ascending bacterial infection is a common cause of stillbirths, but prevention has proven elusive. Many viral infections cause stillbirths but aside from vaccination for common childhood diseases, we do not have a clear prevention strategy. Malaria, because of its high prevalence and extensive placental damage, accounts for large numbers of stillbirths. Intermittent malarial prophylaxis and insecticide-treated bednets should decrease stillbirths. Many infections borne by animals and vectors cause stillbirths, and these types of infections occur frequently in low-income countries. Research that better defines the relation between these infections and stillbirths, and develops strategies to reduce associated adverse outcomes, should play an important part in reduction of stillbirths in low-income countries.

Unexpected intrauterine fetal death in parvovirus B19 fetal infection

Parvovirus B19 infection during pregnancy can be transmitted to the fetus through the placenta. The consequences for the health of the fetus are very variable and can be very serious. They include intrauterine fetal death (IUFD) and miscarriage, which can lead to medico-forensic questions. For the most part, cases of IUFD take place during the second trimester of gestation and present an anatomopathologic picture characteristic of fetal infection with hydrops, placental edema, serous effusion, and erythroblastosis with nuclear inclusions. Endocardial fibroelastosis, medullar and thymic hypoplasia, and hepatic hemosiderosis are frequently present. In the third trimester, the cases are less frequent, not accompanied by hydrops, and can depend more on placental compromise than on direct infection of the fetus. We present 5 cases of IUFD resulting from parvovirus B19 and we discuss the pathogenetic and anatomopathologic aspects and obstetric liability. In 4 cases, the IUFD took place suddenly, in the absence of symptoms, in women who had not previously shown any symptom of the viral infection. In one case, the patient was hospitalized following an ultrasound diagnosis of fetal hydrops and IUFD took place 5 days after admission. Of these cases 3 were verified in the second trimester and 2 in the third trimester. Only the cases of the second trimester and one of the 2 cases of the third trimester presented the characteristic aspects of fetal infection. The other case of third trimester was characterized by placental involvement.

Maternal human parvovirus B19 infection and the risk of fetal death and low birthweight: a case-control study within 35 940 pregnant women

OBJECTIVES

To assess the association between maternal parvovirus B19 infection and fetal death, birthweight and length of gestation.

DESIGN

Case-control study.

SETTING

Population based.

POPULATION

Cases were all 281 women with fetal death within a cohort of 35 940 pregnant woxmen in Norway. The control group consisted of a random sample of 957 women with a live born child.

METHOD

Information on pregnancy outcome was obtained from the Medical Birth Registry of Norway. First trimester serum samples were tested for antibodies against parvovirus B19 (IgM and IgG). In seronegative women, further serum was analysed to detect seroconversion during pregnancy.

MAIN OUTCOME MEASURES

Fetal death, length of gestation and birthweight.

RESULTS

Two of 281 (0.7%) of the women who experienced fetal death and nine of 957 (0.9%) of the controls had presence of IgM antibodies, crude odds ratio 0.8; 95% CI (0.2-3.5). In initially, seronegative women, 3.1% (2/65) with fetal death and 2.6% (8/307) with a live birth seroconverted, crude odds ratio 1.2; 95% CI (0.2-5.7). Presence of maternal parvovirus-specific IgG or IgM antibodies in the first trimester, or seroconversion during pregnancy were not associated with lower birthweight or reduced length of gestation in live born children, but was associated with low birthweight in stillborn offspring.

CONCLUSION

Maternal parvovirus B19 infection was not associated with fetal death in our study. Very few cases of fetal death may be attributed to maternal parvovirus B19 infection.

Infections in Pregnancy

Despite advances in peripartum care, maternal morbidity and mortality associated with infections in pregnancy are increasing even in developed countries. Recently published data from the Center for Disease Control's Pregnancy Mortality Surveillance System indicates that although maternal mortality from hemorrhage, embolism, and anesthesia has declined in the United States, the proportion of maternal deaths due to infections has increased. During 1991–7 infection accounted for 13.2% of pregnancy-related deaths overall and 36.3% of abortion-related deaths. The greatest infection risk is found in blacks, older women, women without prenatal care, and women with multiple pregnancy. In the United States pregnancy rates are stable or increasing in these groups. Infection is also a major cause of morbidity and mortality for the fetus and newborn. Many perinatal infections are associated with intra-uterine growth retardation and low birthweight, or cause fetal and neonatal brain injury. Infections, particularly bacterial vaginosis and chorioamnionitis, can result in preterm delivery of live-born infants (delivery before 37 weeks gestation), or stillbirth. A multitude of immunologic, endocrinologic, metabolic, physiologic, and anatomic changes influence the likelihood and course of many infections during pregnancy. Some of these changes are intrinsic, and occur in all normal pregnancies, while others occur to varying degrees in normal and abnormal pregnancies.

The detection of parvoviruses

Parvovirus B19 is a single-stranded DNA virus which causes severe disease in immunocompromised patients and foetal loss in pregnant women. It is classified as an Erythrovirus and this genus also comprises two related viral genotypes (so-called LaLi/A6 (genotype 2) and V9 (genotype 3)) which appear to be immunologically indistinguishable from Parvovirus B19. Serological and nucleic acid test (NAT) systems to detect Parvovirus B19-mediated infection are commercially available; however, some NAT systems are genotype-specific. International standard preparations of Parvovirus B19 IgG and DNA have been produced for assay standardisation purposes, and to ensure consistency of assay manufacture and performance. Immunological assays, such as B-cell ELISpot, T-cell stimulation, and cytokine detection can also be used to confirm exposure to Parvovirus B19. Immunohistochemical techniques, employing commercially available monoclonal antibodies, are used to localise the virus in infected tissue and Parvovirus B19 viral antigen can also be detected in serum and plasma using antigen-specific ELISA. NAT systems have also been described to detect newly identified parvoviruses such as human bocavirus (HBoV), PARV4, and PARV5, although absolute confirmation of clinical diseases associated with these agents is required. This chapter describes the current status of detection systems for all the aforementioned parvoviruses, with particular emphasis on Erythrovirus detection by serological, NAT, and immunological approaches.

Toll-like receptor 3 activation during pregnancy elicits preeclampsia-like symptoms in rats

BACKGROUND

Preeclampsia (PE), a pregnancy-specific hypertensive syndrome, is one of the leading causes of premature births as well as fetal and maternal death. There is strong evidence that maternal immune system activation, of which Toll-like receptors (TLRs) play a major role, contributes to the development of PE. Viral infections, sensed by TLR3, are associated with hypertensive disorders of pregnancy. We tested the hypothesis that TLR3 activation during pregnancy would cause hypertension, endothelial dysfunction, proteinuria, and intrauterine growth restriction in normal pregnant rats.

METHODS

We treated pregnant and nonpregnant rats with the viral mimetic polyinosinic:polycytidylic acid (poly I:C) or vehicle every other day beginning at day 10 of gestation and measured systolic blood pressure, aortic vasodilation, urinary protein concentration, fetal growth, and serum and placental cytokine levels.

RESULTS

Pregnant rats treated with poly I:C displayed significantly elevated systolic blood pressures compared to pregnant rats and nonpregnant rats treated with poly I:C on day 18 of gestation. Poly I:C-treated pregnant rats also exhibited significantly decreased aortic vasodilation, significantly increased urinary protein concentrations, and had more malformed pups/litter. Additionally, poly I:C-treated rats exhibited a significant increase in placental TLR3 expression and proinflammatory/anti-inflammatory cytokine ratio compared to vehicle-treated rats. Poly I:C treatment of nonpregnant control rats had no effect on systolic blood pressure, aortic vasodilation, or urinary protein concentrations.

CONCLUSION

These findings demonstrate that sustained maternal immune system activation via TLR3 during pregnancy causes PE-like symptoms in rats and suggest that viral infection during pregnancy may contribute to the development of PE.

Infection and stillbirth

Infection may cause stillbirth by several mechanisms, including direct infection, placental damage, and severe maternal illness. Various organisms have been associated with stillbirth, including many bacteria, viruses, and protozoa. In developed countries, between 10% and 25% of stillbirths may be caused by an infection, whereas in developing countries, which have much higher stillbirth rates, the contribution of infection is much greater. In developed countries, ascending bacterial infection, both before and after membrane rupture, with organisms such as Escherichia coli, group B streptococci, and Ureaplasma urealyticum is usually the most common infectious cause of stillbirth. However, in areas where syphilis is prevalent, up to half of all stillbirths may be caused by this infection alone. Malaria may be an important cause of stillbirth in women infected for the first time in pregnancy. The two most important viral causes of stillbirth are parvovirus and Coxsackie virus, although a number of other viral infections appear to be causal. Toxoplasma gondii, Listeria monocytogenes, and the organisms that cause leptospirosis, Q fever, and Lyme disease have all been implicated as etiologic for stillbirth. In certain developing countries, the stillbirth rate is high and the infection-related component so great that achieving a substantial reduction in stillbirth should be possible by reducing maternal infections. However, because infection-related stillbirth is uncommon in developed countries, and because those that do occur are caused by a wide variety of organisms, reducing this etiologic component of stillbirth much further will be difficult.

Parvovirus B19 infection

Human parvovirus B19 (B19) is common in society. Among adults, more than 50% have contracted the infection and immunity is believed to last lifelong. Infection occurs in a few percent of pregnancies, and albeit rare it can then cause fetal anemia, non-immune fetal hydrops and fetal death. Among cases with fetal demise, B19 is found in significant numbers, especially in the second and third trimesters of pregnancy. There is no specific treatment or prophylaxis available against B19 infection, but counseling of non-immune mothers and active monitoring of confirmed maternal infections with intervention to correct fetal anemia is likely to decrease mortality. Passive immunization also has potential to resolve fetal complications, but needs further study.