Editing OBGYN - Embryology
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==Objectives== | ==Objectives== | ||
- | *That there are 4 clinically significant types of anomalies: malformation, disruption, deformation | + | *That there are 4 clinically significant types of anomalies: malformation, disruption, deformation and dysplasia. |
*The causes of congenital anomalies are divided into genetic, environmental and multifactorial. | *The causes of congenital anomalies are divided into genetic, environmental and multifactorial. | ||
*The incidence of major and minor congenital anomalies. | *The incidence of major and minor congenital anomalies. | ||
*Some of the basic principles of teratology. | *Some of the basic principles of teratology. | ||
**You will use this info to counsel patients. | **You will use this info to counsel patients. | ||
- | * | + | *About some examples of teratogenic agents |
- | * | + | *And some examples of major anomalies we frequently see in prenatal diagnosis. |
==Vignette== | ==Vignette== | ||
- | *A 23 yo gravida 1, para 0 | + | *A 23 yo gravida 1, para 0 delivers a baby with rocker bottom feet, spina bifida, and a cardiac defect. |
*Karyotype analysis shows trisomy 18 (47, XY +18). | *Karyotype analysis shows trisomy 18 (47, XY +18). | ||
*You explain to the mother that her son’s anomalies are an example of which basic type: | *You explain to the mother that her son’s anomalies are an example of which basic type: | ||
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*A malformation is defined as a morphological defect of an organ, part of an organ, or larger region of the body that '''results from an intrinsically abnormal developmental process'''. | *A malformation is defined as a morphological defect of an organ, part of an organ, or larger region of the body that '''results from an intrinsically abnormal developmental process'''. | ||
*Intrinsic implies from the beginning such as a chromosomal anomaly present at fertilization. | *Intrinsic implies from the beginning such as a chromosomal anomaly present at fertilization. | ||
- | |||
*Most malformations are considered to be ''a defect of a morphogenetic or developmental field'' which responds as a coordinated unit to embryonic interaction and results in complex or multiple malformation. | *Most malformations are considered to be ''a defect of a morphogenetic or developmental field'' which responds as a coordinated unit to embryonic interaction and results in complex or multiple malformation. | ||
===Disruption=== | ===Disruption=== | ||
*A disruption is a morphological defect of an organ, part of an organ, or body region that '''results from the extrinsic breakdown of or interference with an ''originally normal'' developmental process'''. | *A disruption is a morphological defect of an organ, part of an organ, or body region that '''results from the extrinsic breakdown of or interference with an ''originally normal'' developmental process'''. | ||
- | *Disruption, for an example, | + | *Disruption, for an example, might be caused by a teratogen that causes derailment of a normal development pattern. |
**Teratogens can include drugs or viruses. | **Teratogens can include drugs or viruses. | ||
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**Oligohydramnios can cause clubfoot or Potter's sequence (renal agenesis). | **Oligohydramnios can cause clubfoot or Potter's sequence (renal agenesis). | ||
**Large myomas can cause skull defects. | **Large myomas can cause skull defects. | ||
- | *In deformations, | + | *In deformations, the normal development is mechanically changed to an abnormal state. |
- | + | ||
- | + | ||
===Dysplasia=== | ===Dysplasia=== | ||
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*Examples of dysplasia include renal dysplasia secondary to bladder outlet obstruction. | *Examples of dysplasia include renal dysplasia secondary to bladder outlet obstruction. | ||
**When the bladder is obstructed, hydronephrosis occurs which causes dyshistiogenesis (and is thus called a dysplasia). | **When the bladder is obstructed, hydronephrosis occurs which causes dyshistiogenesis (and is thus called a dysplasia). | ||
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==Vignette== | ==Vignette== | ||
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**normal longitudinal view of spine | **normal longitudinal view of spine | ||
**open spine visible from sagital section | **open spine visible from sagital section | ||
- | **ventriculomegaly | + | **ventriculomegaly |
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5. None of the above are correct | 5. None of the above are correct | ||
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+ | The clubbed feet in this clinical scenario are an example of which type of fetal anomaly: | ||
+ | 1. Malformation | ||
+ | 2. Disruption | ||
+ | '''3. Deformation''' | ||
+ | 4. Dysplasia | ||
+ | 5. None of the above | ||
+ | �==Vignette== | ||
+ | *27 yo gravida 1 para 0 at 20 weeks gestation was found to have a fetus with amniotic band syndrome which has caused complete amputation of the lower fetal arms and legs. | ||
*This type of anomaly would be classified as: | *This type of anomaly would be classified as: | ||
1. Malformation | 1. Malformation | ||
- | '''2. Disruption''' | + | '''2. Disruption''' |
3. Deformation | 3. Deformation | ||
4. Dysplasia | 4. Dysplasia | ||
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*Multifactorial: many common congenital anomalies are caused by genetic and environmental factors acting together in a multifactorial inheritance pattern | *Multifactorial: many common congenital anomalies are caused by genetic and environmental factors acting together in a multifactorial inheritance pattern | ||
- | + | ||
- | + | *Estimated Incidence of Causes of Major Congenital Anomalies Causes: | |
- | + | **Chromosome abnormalities (6-7%) | |
- | + | **Mutant Genes (7-8%) | |
- | + | **Environmental factors (7-10%) | |
- | + | **Multifactorial inheritance (20-25%) | |
- | + | **Unknown etiology (50-60%) | |
- | + | ||
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===Incidence of Anomalies=== | ===Incidence of Anomalies=== | ||
*Anomalies may be single or multiple, major or minor. | *Anomalies may be single or multiple, major or minor. | ||
- | *Single minor anomalies are quite common and occur in approximately 14% of deliveries (ear tags, single umbilical | + | *Single minor anomalies are quite common and occur in approximately 14% of deliveries (ear tags, single umbilical anomaly, hemangiomas). |
*Minor anomalies are of no serious medical significance but may alert clinician to the presence of a major anomalies. | *Minor anomalies are of no serious medical significance but may alert clinician to the presence of a major anomalies. | ||
- | * | + | *90% of infants with 3 or more minor anomalies will have 1 or more major defects. |
- | * | + | *3% of infants born will have a major anomaly. |
*'''Major developmental defects are much more common in early embryos (10-15%)''' than newborn infants (3%) but '''most of them abort spontaneously.''' | *'''Major developmental defects are much more common in early embryos (10-15%)''' than newborn infants (3%) but '''most of them abort spontaneously.''' | ||
*Chromosomal anomalies are present in 50-56% of spontaneously aborted fetuses. | *Chromosomal anomalies are present in 50-56% of spontaneously aborted fetuses. | ||
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====Fragile X Syndrome==== | ====Fragile X Syndrome==== | ||
- | * | + | *Most common inherited cause of mental retardation |
*Frequency of 1/1000-1500 male births | *Frequency of 1/1000-1500 male births | ||
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*Fragile X is due to an unstable repeat of CGG at '''X'''q27. | *Fragile X is due to an unstable repeat of CGG at '''X'''q27. | ||
*All full mutations are dereived from premutation carriers. | *All full mutations are dereived from premutation carriers. | ||
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*Environmental factors account for 7-10% of congenital anomalies. | *Environmental factors account for 7-10% of congenital anomalies. | ||
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*Teratogens cause developmental disruptions following maternal exposure. | *Teratogens cause developmental disruptions following maternal exposure. | ||
*'''Teratogens are not effective until cellular differentiation has begun.''' | *'''Teratogens are not effective until cellular differentiation has begun.''' | ||
*Exact mechanisms by teratogens they induce abnormalities are usually unknown and may be affected by hereditary influences. | *Exact mechanisms by teratogens they induce abnormalities are usually unknown and may be affected by hereditary influences. | ||
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====Congenital Rubella Syndrome==== | ====Congenital Rubella Syndrome==== | ||
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*Vaccination only became available in 1969. | *Vaccination only became available in 1969. | ||
*The disease was dangerous because in children it was almost unnoticeable and pregnant women often did not know that they had been exposed. | *The disease was dangerous because in children it was almost unnoticeable and pregnant women often did not know that they had been exposed. | ||
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**deafness, | **deafness, | ||
**liver, spleen, and bone marrow problems. | **liver, spleen, and bone marrow problems. | ||
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====Thalidomide==== | ====Thalidomide==== | ||
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===Multifactorial inheritance=== | ===Multifactorial inheritance=== | ||
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====Neural Tube Defects==== | ====Neural Tube Defects==== | ||
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====Cleft Lip and Palate==== | ====Cleft Lip and Palate==== | ||
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http://4.bp.blogspot.com/_AL7GK_3BsMM/SHlqr5DZ38I/AAAAAAAAE2A/qOJb0NihTtY/s400/cleft525.jpg | http://4.bp.blogspot.com/_AL7GK_3BsMM/SHlqr5DZ38I/AAAAAAAAE2A/qOJb0NihTtY/s400/cleft525.jpg | ||
- | ===Teratology=== | + | ===Basic principles of Teratology=== |
*The stage of development of an embryo when teratogen is present determines its susceptibility to a teratogen. | *The stage of development of an embryo when teratogen is present determines its susceptibility to a teratogen. | ||
*The most critical period is when cell division, cell differentiation and morphogenesis at are their peak. | *The most critical period is when cell division, cell differentiation and morphogenesis at are their peak. | ||
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http://www.cerebralpalsyinfo.com/CP1.jpg | http://www.cerebralpalsyinfo.com/CP1.jpg | ||
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*Phenytoin (Dilantin) is well known human teratogen '''but only 5-10% of exposed embryos will develop fetal hydantoin syndrome.''' | *Phenytoin (Dilantin) is well known human teratogen '''but only 5-10% of exposed embryos will develop fetal hydantoin syndrome.''' | ||
*Warfarin (Coumadin) exposure during weeks 6-8 causes: | *Warfarin (Coumadin) exposure during weeks 6-8 causes: | ||
- | **15%: nasal hypoplasia, | + | **15%: nasal hypoplasia, stipples epiphyses, hypoplastic phalanges, eye anomalies, mental retardation. |
**20%: fetal loss | **20%: fetal loss | ||
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===Anencephaly=== | ===Anencephaly=== | ||
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===Omphalocele=== | ===Omphalocele=== | ||
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*''Failure of lateral body-fold migration and closure or embryonic persistence of body stalk'' | *''Failure of lateral body-fold migration and closure or embryonic persistence of body stalk'' | ||
*1 per 2,500 births | *1 per 2,500 births | ||
- | *M1:F5 | + | **M1:F5 |
- | + | ||
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*25% have chromosome abnormalities | *25% have chromosome abnormalities | ||
*14% have Beckwith-Wiedemann syndrome | *14% have Beckwith-Wiedemann syndrome | ||
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*Maternal serum screening detects 40% | *Maternal serum screening detects 40% | ||
*Prognosis dependent on assoc anomalies | *Prognosis dependent on assoc anomalies | ||
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*20% do not have liver intrustion. | *20% do not have liver intrustion. | ||
**These (that do not have liver intrusion) are more likely to be chromosomal defects. | **These (that do not have liver intrusion) are more likely to be chromosomal defects. | ||
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*Ultrasound findings can vary and hint at the cause (chromosomal defect or not). | *Ultrasound findings can vary and hint at the cause (chromosomal defect or not). | ||
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*The causes of congenital anomalies are divided into genetic, environmental and multifactorial. | *The causes of congenital anomalies are divided into genetic, environmental and multifactorial. | ||
*The incidence of major and minor congenital anomalies. | *The incidence of major and minor congenital anomalies. | ||
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*Some of the basic principles of teratology. | *Some of the basic principles of teratology. | ||
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