High-risk criteria
To timely identify the infectious process, it is important to assess maternal and neonatal factors. When an intrauterine infection is suspected, the examination is started immediately, in the first hours after birth.
- Maternal factors: a complicated obstetric and gynecological history (stillbirths, habitual miscarriage, birth of children with developmental malformations), complications of the current pregnancy (polyhydramnios, threatened abortion), and labor difficulties (premature rupture of membranes, placental abruption, need for obstetric maneuvers). The woman's infection status before and during delivery plays a huge role.
- Neonatal factors: intrauterine growth restriction (IUGR), birth asphyxia requiring resuscitation, and stigmata of dysembriogenesis. Early manifestation is extremely suspicious: a sharp deterioration in the baby's condition, the appearance of fever in the first two days, or jaundice of unclear etiology.
Laboratory diagnostic methods
Tools for identifying the pathogen or the response to it are divided into two main groups:
- Direct methods. Aimed at detecting the infectious agent itself. The "gold standard" is virological study and bacteriological culture of biological fluids. PCR is also widely used to detect the pathogen's DNA or antigens.
- Indirect methods. Assess the immune response using enzyme-linked immunosorbent assay (ELISA). They detect specific IgM and IgG antibodies. In isolation, such tests have low diagnostic value (10–30%), so they must be properly evaluated dynamically.
Serology interpretation and prognosis
The threat to the fetus directly depends on how the infectious process proceeds in the mother.
- Primary (acute) infection: a previously seronegative woman develops IgM or the pathogen itself. The transmission risk is maximal (over 50%), and the disease in the child more often occurs in a severe generalized form.
- Reactivation (relapse): against the background of a positive PCR, titers of previous IgG rise or new IgM appear. The risk of infection drops to 8%, and a localized form is more common in the newborn.
- Persistent infection: antigens and IgG are present, but IgM are absent. The threat to the fetus is minimal (about 2%), with asymptomatic or mild clinical manifestations.
- Latent infection: low titers of IgG indicate past immunization. The prognosis is favorable: transplacental maternal antibodies provide the child with passive protection for the first 4–6 months of life.
Diagnosis in the newborn
Serological evaluation is performed in the first 7 days, often using the "paired sera" method (comparing maternal and infant blood parameters with an interval of 14–21 days).
- Reliable criterion: detection of IgM in the infant. These macromolecules do not cross the placenta, which proves their independent synthesis by the fetus.
- IgG dynamics: a 4-fold or greater increase in titer compared to the maternal level is considered diagnostically significant.
- Avidity index: high-avidity antibodies are usually acquired from the mother, while low-avidity antibodies confirm the infant's primary own immune response.
Additionally, a complete blood count is performed (anemia, thrombocytopenia, elevated ESR, monocytosis, toxic granulation of neutrophils are characteristic), biochemistry (evaluation of protein and CRP), and urinalysis. Instrumentally, neurosonography (NSG) is used. Brain ultrasound can detect calcifications, cysts, signs of ventriculitis, hemorrhages, and the most dangerous structural change — periventricular leukomalacia.
Diagnostic triad of congenital infections: MAT (Maternal history, Infant clinic, Tests).
Class and exam questions
Is total screening for congenital infections performed for all pregnant women?
No, universal screening for perinatally significant infections is currently absent in global medical practice.
Why is the detection of IgM in a newborn a 100% sign of infection?
Class M immunoglobulins are too large and cannot cross the placental barrier. Their presence means that the child's body has started synthesizing antibodies itself in response to the infection.
What does the detection of low-avidity IgG in an infant indicate?
Low avidity (weak antigen-antibody binding) indicates a primary, recent immune response of the newborn, confirming active infection.
Which lesion on NSG is considered the most severe in congenital infections?
Periventricular leukomalacia. This is a critical brain lesion that subsequently leads to severe neuropsychiatric disability.
What else to study on this topic
- Features of biomaterial collection for bacteriological culture and PCR
- Mechanism of periventricular leukomalacia formation
- Differential diagnosis of jaundice of unclear etiology
- Transplacental transfer of passive immunity
- Interpretation of the "paired sera" method in controversial cases
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