Congenital Defects

Involution Failure

Persistence of Embryonic or Fetal Structures Example: Thyroglossal Duct

Specific for each teratogen

The mechanism of teratogenesis is (blank).

Death

The most common effect of toxic exposure at the pre-implantation stage.

Microcephaly

A component of Rubella Syndrome. Head circumference is less than 13 in (33cm) in newborn baby.

Patent Ductus Arteriosus

A component of Rubella Syndrome. PDA. Persistence of fetal circulation after birth causing perinatal hypoxia.

Teratogens

Chemical, physical, and biologic agents capable of causing anomalies.

Developmental Sequence

A pattern of defects related to a single anomaly. Example: Potter's Complex, oligohydramnios leading to pulmonary hypoplasia.

Agenesis

Absence Example: Renal (blank).

Aplasia

Absence of organ with persistence of rudiment. Example: (Blank) of lung.

Deformation

An abnormal form or position of the fetus due to mechanical force. Usually seen during the 2nd trimester and continuing into the pregnancy. Occurs due to: large fetus, small uterus; large fetus, low amniotic fluid.

Asymmetrical Conjoined Twins

Asymmetric division leads to one normal twin and one rudimentary twin attached. Due to asymmetrical cleavage, each half is unequally divided.

Monotopia

Congenital defect in which a single anomaly leads to a cascade of pathologic defects. Example: Biliary atresia that leads to liver failure.

Polytopia

Congenital defect in which several organs are simultaneously affected.

Polygenic Inherited Disease

Congenital defects arising from a confluence of multiple genetic abnormalities.

Errors of Morphogenesis

Congenital defects arising from abnormal processes giving rise to appearance of organs/tissues etc.

Single Gene Defects

Congenital defects arising from abnormalities in one gene.

Chromosomal Abnormalities

Congenital defects arising from problems in chromosomes themselves.

Dysraphic Anomaly

Defect due to failure of opposed structures to close. Example: Spina Bifida

Atresia

Defects due to incomplete formation of a lumen. Example: Esophageal (blank).

Potter's Complex

Example of multiple defects caused by developmental sequence. Oligohydramnios leading to morphologic changes and pulmonary hypoplasia.

All-or-nothing effect

During pre-implantation or early embryonic stages, exposure to an environmental teratogen has this effect.

Division Failures

Incomplete cleavage of embryonic tissue. Example: Syndactyly

8-10 days after fertilization

Injury during this period leads to incomplete separation of the blastphomere causing symmetric conjoined twins or asymmetric conjoined twins.

Oligohydramnios

Low amniotic fluid.

Malformations

Morphological defects or abnormalities of organs, tissues, or anatomic region.

Developmental Syndrome

Multiple anomalies that are pathogenetically related. Example: Trisomy 13 (Patau's Syndrome). Baby is born with: single frontal lobe, single cerebral ventricle, one median eye, absent olfactory bulbs, and failure of formation of nasal structures.

Developmental Association or Syntropy

Multiple anomalies that are statistically associated by do not share a pathogenetic mechanism. Example: Babies born to mothers who took "Bendectin" for morning sickness were born with both stomach and talus deformities.

Ectopia

Outside of the normal anatomic site. Example: (Blank) testicle.

Hypoplasia

Reduced size due to incomplete development. Example: (Blank) heart

Dystopia

Retention of an organ at its site of embryonic development. Example: Cryptorchidism

Microcephaly, PDA, Cataracts

Rubella Syndrome

Cortical Blindness

Seen due to cataracts in newborns, often due to prenatal exposure to Rubella. Light fails to reach the brain through the retina and the brain fails to develop the ability to interpret seen images.

Developmental Stage

Susceptibility to teratogens is specific for each (blank). Example: Maternal rubella during the 1st trimester.

Symmetrical Conjoined Twins

Symmetric division leads to conjoined twins joined at any point. Due to symmetrical division of the blastphomere, each half receives an equal share.

Toxoplasmosis Other Rubella Cytomegalo Inclusive Virus Herpes

TORCH Complex. Similar signs and symptoms produced by fetal and/or neonatal exposure to one of several viral organisms. Injury is dependent upon timing but generally results in: calcifications in the brain, deformity of the eye, blindness, and deformity of the heart.

Dose Dependent

Teratogenesis is (blank). No safe levels have been established, therefore, all exposures should be avoided, especially during pregnancy.

Organogenesis

Teratogenic exposure rarely causes a morphogenic error after the occurrence of this process.

1st Trimester

The period of time during pregnancy when susceptibility to teratogens is typically greatest.

Genetic Make-Up

The principle determinant of susceptibility to teratogens. Example: Some babies of alcoholic mothers have FAS while others do not.

Teratology

The study of developmental anomalies.

4th Month

When is susceptibility to the development of a cleft palate greatest?