1a Disorders of Early Development Flashcards
What can cause pregnancy loss in humans?
- Errors in embryo-fetal development
- Failure of the embryo to implant in the uterine lining
- Inability to sustain development of the implanted embryo
What is meant by a miscarriage?
Loss of pregnancy before 23 weeks gestation
What is the definition of a early clinical pregnancy loss?
Loss before 12 weeks gestation
What is meant by a late clinical pregnancy loss?
Loss of pregnancy after 24 weeks gestation
What is meant by recurrent misscarriage?
In the UK, defined as three or more pregnancy losses
US: two or more pregnancy losses
What is the major cause of early pregnancy loss?
Aneuploidy (chromosome number errors)
How does the risk of trisomic pregnancy increase with materal age?
Exponential increase
Why does aneuploidy increase with maternal age?
As the mother gets older, the cohesion proteins which hold the chromatids of homologous chromosomes together are degraded, leading to a loss of cohesion between the chromatids - results in the chromatids separating and drifting during mitotic division rather than being segregated accurately
What is the name of two cohesion proteins involved in maintaining cohesion between chromatids within chromosomes?
REC8 and SMC2
What proportion of conceptions are lost before the pregnancy is detectable by ultrasound scan?
50%
What do embryos require to be viable?
Meternally and paternally derived genomes
What happens when the spindle cannot grad a hold of the chromatids peoperly?
Leads to non-disjunction leading to aneuploidy
What causes a complete molar pregnancy?
When an empty egg is fertilised by one or two sperm, resulting in all the genetic material from the father
What is meant by a partial /incomplete molar pregnancy?
When a normal egg is fertilised by two sperm, so the embryo has three sets of chromosomes
Which genome drives placental development?
Paternal genome
Which genes are only expressed from the paternally inherited copy?
genes which promote the embryos fitness to survive at the expense of the mother
Which genes are only expressed from the maternally inherited copy?
Genes which restrict embryo fitness to conserve resources for future pregnancies
What happens genetically when there is a molar pregnancy?
There is a genetic imbalance - eg if more paternal genes are expressed, there will be less of a balance and placenta will be enlarged
Why do complete molar pregnancies result in enlarged placentas?
There is a genomic imbalance, meaning more paternally-inherited genes are expressed, leading to a lot of placental development
What are gestational trophoblastic diseases?
A collection of disorders characterized by overgrowth of trophoblastic tissue
What is the difference between a complete and partial hydatidiform mole?
in a complete hydatidiform mole, there is no fetal tissue, but there is fetal tissue in a partial one
What is an example of a benign gestational trophoblastic disease?
Hydatidiform mole
What forms when the gestational trophoblastic disease becomes malignant?
Forms a gestational trophoblastic neoplasia
What are rare examples of malignant gestational trophoblastic neoplasias?
Invasive moles, Choriocarcinoma
