ABSTRACT
DEFECTS OF BLASTOGENESIS (FIRST 28 DAYS OF DEVELOPMENT)
severe brain and heart anomalies
DEFECTS OF ORGANOGENESIS (29-56 DAYS OF DEVELOPMENT)
the body ●● Meckel diverticulum, persistent urachus, ata-
visms (recurrence of a trait that is typical of an ancestral form, evolutionary throwback)
DEFECTS OF PHENOGENESIS (57-266 DAYS OF DEVELOPMENT, FETAL STAGE)
DEFECTS OF POSTNATAL LIFE
●● Neoteny (persistence of juvenile features in adult form), physiological development slowed
●● Functional defects, dysplasia, altered hemostasis
TRIPLE SCREEN TEST
●● Maternal blood screening test for alphafetoprotein (AFP), unconjugated estriol, and beta-HCG
●● If positive; indicates high risk of Down syndrome, Edwards syndrome, or neural tube defects
AMNIOTIC FLUID
●● Amniocentesis performed at 14 weeks’ gestation
cholinesterase; indicates open neural tube defects
CHORIONIC VILLUS SAMPLING
PREIMPLANTATION GENETIC DIAGNOSIS (PGD)
tocyst biopsy
PERIPHERAL BLOOD
SKIN AND SOFT TISSUE
TRADITIONAL CYTOGENETICS-FISH
●● Interphase (touch prep, tissue sections, frozen tissue)
a particular portion of genome, for example, velocardiofacial syndrome del 22q11.2 (DiGeorge syndrome)
SUBTELOMERIC CHROMOSOMAL REARRANGEMENTS
●● Detection of facioscapulohumeral muscular dystrophy, Alzheimer disease
COMPARATIVE GENOMIC HYBRIDIZATION (CGH)
●● Technique that allows detection of loss/ gain of DNA across entire genome
●● No prior knowledge of specific chromosome abnormality
●● Used to screen loss/gain of particular chromosomal regions
●● When cytogenetic abnormality is confined to the placenta only and not to the fetal tissue
TYPE 1
●● When aneuploid cells are confined to the trophoblast with chromosomally normal stroma (most common)
TYPE 2
●● When aneuploid cells are confined to the chorionic stroma
TYPE 3
●● When aneuploid cells are confined to both trophoblast and the stroma
●● Most frequently seen in spontaneous abortions
large middle temporal gyrus
●● Heart: Atrioventricular canal defects (atrial septal defect and ventricular septal defect)
●● Hematological abnormalities: Polycythemia, leukemia (congenital acute myeloid leukemia, acute lymphoblastic leukemia in childhood, acute megakaryocytic leukemia, transient myeloproliferative disorder of infancy)
●● Clinodactyly: Curvature of fifth finger toward adjacent four fingers
●● Single palmer crease and absence of middle crease in fifth finger
EDWARD SYNDROME (TRISOMY 18)
●● Triangular facies, microcephaly, micrognathia, hypertelorism, horse-shoe kidney, rocker-bottom feet, overlapping second and third digits, clenched hands
PATAU SYNDROME (TRISOMY 13)
●● Midline facial defects, cebocephaly (ocular hypotelorism and single nostril), alobar holoprosencephaly, aplasia cutis, postaxial polydactyly, appendiceal diverticula (dinosaur tail), fusion of spleen and pancreas
TRISOMY 16
●● Common in embryos and fetuses that abort early during gestation
gynecomastia, arachnodactyly, atrophic testicles with hypoplastic clusters of Leydig cells). Prone to develop teratomas
●● 45X/45XY-Turner syndrome-monosomy X, present as hydrops fetalis (infantile female external genitalia, streak-gonads, co-arctation of aorta, rarely fertile). If mosaicism for Y chromosome → prone to develop gonadoblastoma
DIGYNIC
small and thin limbs ●● Placenta very small, hypoplastic with no
features of partial mole ●● Marked adrenal hypoplasia ●● Failure of division during meiosis I or II ●● Maternal serum shows decreased estriol
and HCG ●● Outcome: Spontaneous abortion/stillbirth
DIANDRIC
tial hydatidiform mole ●● Fertilization of normal oocyte by two
spermatocytes ●● Maternal serum shows increased AFP
and HCG ●● Outcome: Spontaneous abortion
●● Should be differentiated from hydropic abortion (degenerative changes)
COMPLETE HYDATIDIFORM MOLE
father only (androgenesis) ●● P57 (KIP2) immunostaining of cytotropho-
blast and villus stroma = negative because of absence of maternal genome
PARTIAL HYDATIDIFORM MOLE
and two sets of paternal genes
LISTERIOSIS
●● Listeria monocytogenes (Gram-positive bacilli)
●● Consumption of unpasteurized milk products and processed meats
●● Presence of small white abscesses on fetal skin, viscera, and placental villi
VIRAL INFECTIONS SUCH AS CYTOMEGALOVIRUS (CMV)
●● Fetal viscera and placenta show lymphoplasmacytic infiltrate and CMV inclusions
●● Common presentation is fetal death in second trimester
●● Range of etiology is vast; chromosomal defects, infections, hemoglobinopathies, cardiac arrhythmias, metabolic disorders, and congenital pulmonary airway malformation
●● Monozygous twins more prone to intrauterine fetal demise due to vascular anastomosis leading to twin-to-twin transfusion syndrome and twin reversed arterial perfusion
