disorders of early development Flashcards
what are some causes of pregnancy loss (common in humans)
errors in embryo fetal development
failure of the embryo to implant in the uterine lining
inability to sustain development of an implanted embryo/fetus
what is a miscarriage
loss of a pregnancy prior to ~23 weeks gestation
when is early clinical pregnancy loss
<12 weeks gestation
when is late clinical pregnancy loss
> 24 weekends
what is recurrent miscarriage (RM)/Recurrent Pregnancy Loss (RPL)
3 or more losses (consecutive or nonconsecutive)
what are the major causes of early pregnancy loss
major driver likely to be aneuploidy (chromosome number error) in embryo
~53% embryos created using donor eggs in IVF are aneuploid
~50% of lost early pregnancies display chromosomal errors
exponential increase in risk of trisomic pregnancy with increasing maternal age
what can oocytes experience
oocytes are cells in the ovary which may undergo meiotic division to form an ovum
prolonged meiotic arrest
when does recombination occur in testes and ovaries
two chromatids > exchange of genetic material (in testes, after recombination occurs - 1st and 2nd meiotic division occurs straight after) whereas (in ovaries, after recombination - goes into rest until ovulation)
what do cohesin proteins do
throughout meiotic arrest, the chromatids of homologous chromosomes are held together by cohesin proteins
how does cohesion get lost with increasing age
these cohesin proteins are not replaced, leading to loss of cohesion between chromatids with increasing age of the oocyte
what happens when cohesion is lost
if cohesion has been lost, chromatids can separate and drift during meiotic division rather than being segregated accurately by the spindle
what happens when some genes are only expressed from the paternally-inherited copy
promote embryo fitness at the expense of the mother (overgrowth of placenta)
what happens when some genes only expressed from the maternally-inherited copy
restrict embryo fitness to conserve resources for future pregnancies (undergrowth of placenta)
what are GTDs - Gestational Trophoblastic Diseases
GTDs are a collection of disorders characterised by overgrowth of trophoblastic tissue
what are benign GTDs
hydatidiform moles
what are complete hydatidiform moles
fetal tissue absent
what are partial hydatidiform moles
fetal tissue present
what are malignant GTDs
gestational trophoblastic neoplasias
what are rare gestational trophoblastic neoplasias
invasive mole
choriocarcinoma
what are very rare gestational trophoblastic neoplasias
placental site trophoblastic tumour (PSTT)
epithelioid trophoblastic tumour
how do complete hydatidiform moles arise
empty egg fertilised by (no maternal DNA)
1x sperm then sperm genome duplicated
or 2x sperm and there is no duplication
how do partial hydatidiform moles arise
normal egg fertilised by (maternal DNA)
1x sperm then sperm genome duplicated
or 2x sperm and no duplication
failure to recognise and clear failed pregnancy?
HM they are benign and should be surgically removed, if left to develop further - can become cancerous
what is ectopic pregnancy - extra-uterine implantation
implantation of the embryo at a site other than the uterine endometrium
98% of these implantation events occur in the fallopian tube
other sites include ovary, cervix, other intra-abdominal sites
