Ultrasound Findings of Fetal Infections: Current Knowledge

Infectious diseases during pregnancy are still a major cause of fetal mortality and morbidity worldwide. The most common teratogenic pathogens are cytomegalovirus (CMV), varicella-zoster virus (VZV), rubeovirus, parvovirus B19, herpes simplex virus (HSV), Toxoplasma gondii, Treponema pallidum and the emergent Zika virus (ZIKV). Ultrasound findings include cerebral anomalies, orbital defects, micrognathia, cardiac defects, hepatosplenomegaly, liver calcifications, abdominal anomalies, skin and limb anomalies, edema, placental and amniotic fluid anomalies and altered Doppler analyses. The classification of ultrasound markers of congenital infections by anatomical region is reported to guide differential diagnosis and prenatal care.

Maternal Parvovirus B19 Infection Causing First-Trimester Increased Nuchal Translucency and Fetal Hydrops

This is a case report of a 31-year-old primigravida who was diagnosed with an asymptomatic acute parvovirus B19 infection in the second trimester of pregnancy and its suspected association with an increased nuchal translucency (NT) measurement. Parvovirus B19 is a single-stranded DNA virus that is cytotoxic to erythroid progenitor cells, causing inhibition of erythropoiesis. While maternal disease is usually mild, fetal infection can result in spontaneous abortion, aplastic anemia, nonimmune fetal hydrops, and fetal demise. This fetus had an increased NT of 3.2 mm at 11 weeks' gestation with a normal male karyotype and microarray analysis on chorionic villi sampling, in addition to a normal fetal echocardiogram at 15 weeks' gestation. The anatomy scan at 20 weeks' and 1-day gestation revealed fetal ascites, pleural effusion, and increased middle cerebral artery peak systolic velocity suspicious for fetal anemia. At this time, maternal serology for parvovirus was positive for IgM and IgG. Amniocentesis, cordocentesis, and intrauterine transfusion were performed. The amniocentesis revealed elevated parvovirus B19 DNA, quantitative PCR (2,589,801 copies/mL, reference range <100 copies/mL). The patient delivered a viable male fetus at 37 weeks' and 6-day gestation, without sequelae of the previously noted hydrops. Parvovirus B19 infection should be a consideration when evaluating increased NT and hydrops fetalis. It warrants close antepartum surveillance and possible intrauterine fetal transfusions. With prompt recognition, proper treatment, and surveillance, these patients can go on to achieve healthy term deliveries. Long-term outcomes of delivered infants require further study.

Human Parvoviruses

Parvovirus B19 (B19V) and human bocavirus 1 (HBoV1), members of the large Parvoviridae family, are human pathogens responsible for a variety of diseases. For B19V in particular, host features determine disease manifestations. These viruses are prevalent worldwide and are culturable in vitro, and serological and molecular assays are available but require careful interpretation of results. Additional human parvoviruses, including HBoV2 to -4, human parvovirus 4 (PARV4), and human bufavirus (BuV) are also reviewed. The full spectrum of parvovirus disease in humans has yet to be established. Candidate recombinant B19V vaccines have been developed but may not be commercially feasible. We review relevant features of the molecular and cellular biology of these viruses, and the human immune response that they elicit, which have allowed a deep understanding of pathophysiology.

Ductus Venosus: A Love Story of 14 Years

Ductus venosus is a tiny vessel with a central role in fetal circulation. Combining B-mode with color and pulsed Doppler is feasible to identify this vessel and evaluate the blood flow waveform at 11 to 13 weeks. The higher prevalence of abnormal A-wave in fetuses with abnormal karyotype and/or cardiac defects turned DV evaluation into a useful marker for chromosomal abnormalities and cardiopathies. Even when combined with nuchal translucency (NT) or biochemical markers, DV blood flow evaluation contributes to an increase in sensitivity and reduces false-positive rate. Abnormal ductal flow is also related to a worse fetal and perinatal outcome. In monochorionic twin pregnancies, in addition to NT measurement at 11 to 14 weeks, the Doppler assessment of DV blood flow increases relevantly the performance of screening for those at higher risk of developing twin-to-twin transfusion syndrome. This story of 14 years surely contributed to change the way first trimester screening is being implemented.