ABPath Pediatric Pathology key terms

The flat cluster of cells formed in week 2 that becomes trilaminar in week 3 when gastrulation creates ectoderm, mesoderm, and endoderm; all subsequent organ systems derive from these three germ layers.

The process in the third week of development in which epiblast cells migrate through the primitive streak to form the three definitive germ layers, establishing the body axes and the notochord.

Fusion of neural folds to form the neural tube, beginning around day 22 at the cervical region and completing cranially and caudally by day 28; failure produces anencephaly or spina bifida.

Periconceptional folic acid intake that reduces the risk of neural tube defects by promoting nucleotide synthesis and methylation; recommended for all women of childbearing potential and at higher doses after an affected pregnancy.

Gestational age is time since the first day of the last menstrual period; postmenstrual age is gestational age plus postnatal age, used to plot growth and assess maturation in preterm infants.

Birth weight below the 10th percentile for gestational age, which may reflect constitutional smallness or pathologic fetal growth restriction with increased perinatal morbidity and mortality.

Pathologic failure of a fetus to reach its genetic growth potential, often from placental insufficiency, infection, or chromosomal abnormality; distinguished from constitutionally small infants by growth velocity and Doppler findings.

A postnatal examination of neuromuscular and physical maturity signs used to estimate gestational age in newborns, particularly when prenatal dating is unavailable or unreliable.

Prenatal blood testing of maternal analytes such as alpha-fetoprotein, hCG, unconjugated estriol, and inhibin A to estimate risk of aneuploidy, neural tube defects, and adverse pregnancy outcomes.

Noninvasive prenatal testing that analyzes placental-derived cell-free DNA in maternal plasma to screen for common trisomies and sex chromosome abnormalities, with high sensitivity but requiring diagnostic confirmation.

The immunologic adaptations of pregnancy, including altered T-cell subsets, regulatory T cells, and HLA-G expression at the trophoblast interface, that permit survival of the semi-allogeneic fetus.

Maternal antibody formation against fetal red cell Rh D antigen after fetomaternal hemorrhage, causing hemolytic disease of the fetus and newborn; prevented by antenatal anti-D immune globulin.

Abnormal accumulation of fluid in at least two fetal compartments, such as ascites, pleural effusion, pericardial effusion, or skin edema; causes include immune hemolysis, parvovirus, structural anomalies, and aneuploidy.

Inadequate maternal-fetal exchange due to placental vascular or villous abnormality, producing fetal growth restriction, oligohydramnios, and increased perinatal risk.

Reduced amniotic fluid volume, most often from fetal renal agenesis, urinary tract obstruction, or placental insufficiency; can cause pulmonary hypoplasia and limb compression deformities.

Premature separation of a normally implanted placenta from the uterine wall, presenting with vaginal bleeding, uterine tenderness, and fetal distress; a major cause of perinatal death.

Death of a fetus in utero at 20 weeks gestation or later, evaluated by placental examination, autopsy, karyotype or microarray, and maternal serology to identify a cause.

Systematic workup after fetal death including placental histopathology, fetal autopsy, cytogenetic or molecular testing, and maternal laboratory studies to determine cause and recurrence risk.

Skin changes of a fetus that died in utero, with reddening, desquamation, and eventual dark discoloration reflecting the interval between death and delivery.

An acquired inflammatory and ischemic necrosis of the neonatal bowel, typically in preterm infants, with pneumatosis intestinalis, feeding intolerance, and risk of perforation and short bowel syndrome.

Chronic lung disease of prematurity characterized by arrested alveolarization and dysmorphic vascular growth, resulting from injury to immature lungs by ventilation, oxygen, and inflammation.

Disordered retinal vascular proliferation in premature infants exposed to hyperoxia and dysregulated growth factors, which can progress to retinal detachment and vision loss.

The cascade of oligohydramnios causing pulmonary hypoplasia, limb deformities, and characteristic facial features, classically resulting from bilateral renal agenesis.

Failure of one or both kidneys to form because of defective ureteric bud induction of metanephric mesenchyme; bilateral agenesis is lethal from pulmonary hypoplasia.

A nonrandom co-occurrence of vertebral anomalies, anal atresia, cardiac defects, tracheoesophageal fistula, renal anomalies, and limb defects, diagnosed when at least three features are present.

A multiple malformation disorder with coloboma, heart defects, choanal atresia, growth retardation, genital anomalies, and ear anomalies, usually caused by CHD7 mutations.

Population-based testing of dried blood spots shortly after birth for treatable metabolic, endocrine, hematologic, and other disorders, requiring timely confirmation and follow-up.

Autosomal recessive deficiency of phenylalanine hydroxylase causing phenylalanine accumulation and intellectual disability if untreated; detected by newborn screening and managed with dietary restriction.

A group of inherited disorders with defective T-cell development and function, presenting in infancy with infections, failure to thrive, and lymphopenia; fatal without hematopoietic stem cell transplantation.

A disorder of motile cilia causing chronic sinopulmonary disease, situs inversus in some patients, and male infertility, inherited mostly in an autosomal recessive pattern.

A group of congenital infections including Toxoplasma, syphilis, rubella, cytomegalovirus, and herpes simplex that cause similar patterns of growth restriction, rash, and neurologic injury.

Congenital cytomegalovirus infection producing periventricular calcifications, microcephaly, sensorineural hearing loss, and large intranuclear inclusions in affected tissues.

A congenital infection that targets erythroid progenitors, causing severe fetal anemia, nonimmune hydrops, and occasionally myocarditis; confirmed by maternal serology and fetal DNA testing.

The most common pediatric renal malignancy, composed of blastema, epithelium, and stroma, associated with WT1 and WT2 abnormalities and with Beckwith-Wiedemann and WAGR syndromes.

An embryonal tumor of sympathetic neural crest origin, most often in the adrenal medulla, with N-myc amplification and catecholamine metabolite elevation; prognosis varies with age and stage.

An overgrowth disorder with macrosomia, macroglossia, omphalocele, hemihyperplasia, and embryonal tumor risk, caused by dysregulation of imprinted genes at chromosome 11p15.

G-banded karyotype detects balanced rearrangements and aneuploidy but requires dividing cells, whereas microarray detects submicroscopic copy-number changes without culture and is preferred for many developmental and prenatal indications.

A technique using labeled DNA probes to detect specific chromosomal sequences in interphase or metaphase cells, useful for rapid aneuploidy assessment and gene amplification such as N-myc.

An analytic method measuring multiple analytes simultaneously from dried blood spots to detect amino acid, organic acid, and fatty acid oxidation disorders with high throughput.

Thrombocytopenia in a fetus or newborn caused by maternal antibodies against paternal platelet antigens, requiring antigen-matched platelet transfusion and IVIG; a key pediatric transfusion medicine problem.

A test detecting antibody or complement coating red cells in vivo, central to diagnosing hemolytic disease of the newborn and autoimmune hemolysis.

Postmortem examination of a fetus or infant incorporating external examination, radiographs, organ dissection, histology, and ancillary studies to establish cause of death and recurrence risk.

Death of an infant under one year that is unexpected by history, investigated with scene examination, autopsy, and review of records to distinguish natural causes, accidental suffocation, and inflicted injury.

External quality assessment in which a laboratory's results on unknown specimens are compared with peer laboratories to verify analytic performance and satisfy accreditation requirements.

Quality control monitors individual analytic runs against acceptance criteria, whereas quality assurance encompasses the broader system of policies, audits, and process improvement ensuring overall laboratory quality.

A laboratory rule flagging a result that differs from a patient's prior value by more than a defined threshold, prompting review for specimen mix-up, analytic error, or true clinical change.