Maternal and fetal infection

Although their incidence varies among populations, maternal-fetal infections are increasingly recognized to be among the most common causes of maternal and perinatal morbidity. The use of new techniques, including nucleic acid hybridization and direct fetal or trophoblastic cell sampling, continues to accelerate our knowledge of the epidemiology, microbiology, and immunology, as well as means to diagnose, treat, and prevent individual congenitally transmitted infections. Given the number and complexity of these infections, only selected aspects of recent advances are presented.

MR imaging of brain maturation in normal and developmentally handicapped children

White matter myelination was assessed in the frontal, temporal, and occipital lobes and in the internal capsule in 91 neurodevelopmentally handicapped infants on T2-weighted images (spin echo 3,000/120 ms) and compared with myelination scores from 53 normal control subjects. Clinical diagnosis was birth asphyxia (34), seizures with delays of various causes (33), congenital infections (15), and intracerebral hemorrhages (9). Myelination in the total group of patients was generally delayed. However, we found distinct differences in myelin deposition between groups. Myelination of handicapped children with seizures or with intrauterine infections was retarded most severely at all ages. Children with intracerebral hemorrhages were almost never significantly different from normals in any part of the brain, whereas children with birth asphyxia had myelination scores in between. We conclude that magnetic resonance staging of developmental processes, such as myelination, in the infants' brain helps to recognize delays at an early age.

The risk of neonatal infection following prolonged rupture of the fetal membranes

Over a seven month period in 1986, 164 (1.1%) of a total 15,131 neonates delivered in the Maternity Hospital, Kuala Lumpur were born to mothers with prolonged rupture of the fetal membranes. Septic work-ups were performed on 163 of these babies shortly after birth, 77 of them had no bacteriological, radiological or other clinical evidence of infection. The remaining 86 had additional history of illness. Nine of these 86 babies had proven infection: four with septicemia, one with meningitis and four others with congenital pneumonia. This study showed that neonates had risk of infection only when maternal history of prolonged rupture of the fetal membranes was associated with other clinical evidence of infection. However, even in this group of neonates at risk, 89.5% of them were not infected. Therefore, there is still a need to develop a simple, rapid, reliable and cheap laboratory method to help early identification of the infected from the non-infected neonates in order to prevent unnecessary antibiotic treatment and hospital stay.

Mechanisms and pathways of congenital infections

Fetal and neonatal infections can occur at different times during pregnancy, from conception to birth. Infections that take place near the time of conception often destroy the zygote or embryo and only rarely leave definitive evidence. The mother can transmit the infection to her fetus through several routes, but the most likely routes are through ascending infections and through the blood. The inability of most agents to infect the early embryo probably depends largely on local barriers to the infectious agent, such as the zona pellucida. Some viruses, however, because of their systems for gene regulation of expression, can infect only embryos of certain developmental stages. Certain retroviruses can infect embryos, integrate into cellular DNA, and become part of the germline. After implantation, most infectious agents reach the fetus hematogenously. Organisms circulating in the mother reach and infect the placenta. They then may breach the placenta, gain access to the fetal circulation, and disseminate through the fetal body. Agents with particular tropisms infect particular organs and cause particular symptom complexes. The damage done by the organisms depends largely on the gestational age of the fetus at the time of the infection. The ability of the agent to infect or damage the fetus at all often depends on whether the mother is experiencing a primary infection or has previously mounted an effective immune response. Agents harm the fetus through direct destruction of parenchymal cells, through destruction of blood vessels and resulting infarction, through continued replication in fetal and neonatal tissues, through altering the growth parameters of various fetal tissues, and through provoking autoimmune responses. Infections that begin in the perinatal period usually infect the fetus by direct inoculation from infected foci in the birth canal or through direct contact with large amounts of infected maternal body fluids. Direct tissue destruction of the immediate sequelae of invasive infections usually causes the fetal damage from these perinatally acquired agents. The clinical features of the disease that begin in this period provide an opportunity for effective therapeutic intervention. Understanding the routes of fetal infection and the mechanisms underlying fetal damage from infection will help in devising strategies for preventing and treating congenital infections.

A practical guide to the diagnosis of congenital infections in the newborn infant

Every attempt should be made to identify an etiologic agent in infants with suspected congenital infection. Some of the infections are treatable, such as herpes simplex, syphilis, and toxoplasmosis. For other infectious agents (i.e., CMV and rubella), close follow-up will enable early detection of hearing impairment and permit early educational intervention. In addition, appropriate isolation measures will reduce the risk of nosocomial infections due to herpes simplex, rubella, hepatitis B, and CMV. Rational use of the available diagnostic tools will enable detection of most symptomatic congenitally infected neonates at a reasonable cost.