Chapter 9 Flashcards
___, ___, and ___ are synonymous terms used to describe structural, behavioral, functional, and metabolic disorders present at birth
Birth defect, congenital malformation, and
congenital anomaly
Terms used to describe the study of these disorders are ___ and ___
teratology and dysmorphology
____ occur in approximately 15% of newborns. These structural abnormalities, such as microtia (small ears), pigmented spots, and short ____, are not themselves detrimental to health but, in some cases, are associated with major defects
Minor anomalies - palpebral fissures
Therefore, the critical period for causing most structural birth defects extends from ____
fertilization through the eighth week of gestation
Many ___ occur during formation of structures, for example, during the period of organogenesis that extends from the beginning of the ____
malformations - third to the end of the eighth week of gestation
Although this tenet holds true for many insults to normal development, it is important to note that ___ begins late in the ___ at the blastocyst stage and that a great variety of birth defects can be caused by disruptions in cell signaling during specification of the cranial-caudal and left-right axes
axis formation - first week
___ result in morphological alterations of already formed structures and are
caused by destructive processes. Vascular accidents leading to transverse limb defects and defects produced by amniotic bands are examples
Disruptions
A ___ is a group of anomalies occurring together that have a specific common cause. This term indicates that a diagnosis has been made and that the risk of recurrence is known
syndrome
___ result from mechanical forces
that mold a part of the fetus over a prolonged period. Clubfeet, for example, are caused by compression in the amniotic cavity. often involve the musculoskeletal system and may be reversible postnatally
Deformations
In contrast, ___ is the nonrandom appearance of two or more anomalies that occur together more frequently than by chance alone, but the cause has not been determined. An example is the VACTERL association (vertebral anomalies, anal atresia, cardiac defects, tracheoesophageal fistula, renal anomalies, and limb defects)
association
In 1961, observations by W. Lenz linked limb defects to the sedative ___ and made it clear that drugs could also cross the placenta and produce birth defects
thalidomide
Since that time, many agents have been identified as ___ (factors that cause birth defects)
teratogens
Birth defects due to ___ (German measles) during pregnancy (congenital rubella syndrome) used to be a major problem, but development and widespread use of a vaccine have nearly eliminated congenital malformations from this cause
rubella
Factors determining the capacity of an agent to produce birth defects have been defined and set forth as the ____
principles of teratology
___ and ___ can cause birth defects. Herpes-induced abnormalities are rare, and usually, infection is transmitted to the child during delivery, causing severe illness and sometimes death. Intrauterine
infection with the latter scarring of the skin, limb hypoplasia, and defects of the eyes and central nervous system
Herpes simplex virus and varicella virus
___ is a serious threat. Often, the mother has no symptoms, but the effects on
the fetus can be devastating. The infection can cause serious illness at birth and is sometimes fatal. On the other hand, some infants are asymptomatic at birth but develop abnormalities later, including hearing loss, visual impairment, and intellectual disability
Cytomegalovirus
___ causes ___ following transmission of the virus from an infected mother to her unborn child. Infections late in the first trimester (7 to 12 weeks) are the most likely to harm the fetus, although abnormalities have been observed following infections up to 18 weeks
Zika Virus causes congenital Zika syndrome (CZS)
Zika infection causes a unique pattern of birth defects in affected children including (1) ____ with overlapping cranial sutures, redundant scalp skin, and a prominent occipital bone
(2) thinning of the cerebral cortex with abnormal gyri and subcortical calcification (3) microphthalmia and coloboma
(4) joint contractures (arthrogryposis)
(5) neurological sequelae, including motor and cognitive deficits
severe microcephaly
___ can cause birth defects. Poorly cooked meat; feces of domestic animals, especially cats; and soil contaminated with feces can carry the protozoan parasite Toxoplasmosis gondii. A characteristic feature of this infection is cerebral calcifications
Toxoplasmosis
____ kills rapidly proliferating cells, so it is a potent teratogen, producing virtually any type of birth defect depending on the dose and stage of development of the concepts at the time of exposure
Ionizing radiation
One example is ___, an antinauseant and sleeping pill. In 1961, it was noted in West Germany that the frequency of amelia and meromelia (total or partial absence of the extremities), a rare abnormality that was usually inherited, had suddenly increased
thalidomide
One example is thalidomide, an antinauseant and sleeping pill. In 1961, it was noted in West Germany that the frequency of __ and __ (total or partial absence of the extremities), a rare abnormality that was usually inherited, had suddenly increased
amelia and meromelia
___, an analogue of Vitamin A, has been shown to cause a characteristic pattern of malformations known as the isotretinoin embryopathy
Isotretinoin (Accutane)
Isotretinoin (Accutane), an analogue of ____ has been shown to cause a characteristic pattern of malformations known as the isotretinoin embryopathy
Vitamin A
Isotretinoin (Accutane), an analogue of Vitamin A, has been shown to cause a characteristic pattern of malformations known as the ____
isotretinoin embryopathy
Other drugs with teratogenic potential include the ___, ____, and ____, which are used by women who have seizure disorders
anticonvulsants diphenylhydantoin (phenytoin), valproic acid, and trimethadione
Specifically, trimethadione and diphenylhydantoin produce a broad spectrum of abnormalities that constitute distinct patterns of dysmorphogenesis known as the___ and ___. Facial clefts
are particularly common in these syndromes
trimethadione and fetal hydantoin syndromes
The anticonvulsant ___ increases the risk for several defects, including atrial septal defects (ASD), cleft palate, hypospadias, polydactyly, and craniosynostosis, but the highest risk is for the neural tube defect, spina bifida
valproic acid
