INTRODUCTION
Polyploidy is caused by one or more complete (haploid)
sets of extra chromosomes. Triploidy (3n) is caused
by one extra set of chromosomes, mostly 69XXY and
tetraploidy (4n) by two extras sets, e.g. 92XXXX.
Many affected pregnancies are lost spontaneously
as miscarriages and polyploidy occurs in 20% of all
chromosomally abnormal spontaneous abortions.
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ANTENATAL
The clinical expression of polyploidy depends on
the source of the additional haploid set of chromosomes.
If the extra set is paternally derived (diandry)
the fetus has a large head and small body (i.e. head
sparing growth retardation) and the placenta is large
and cystic with molar changes. If the extra set is
maternal in origin (digyny) the fetus is severely
growth retarded and the placenta is small. Syndactyly
is frequently present between the third & fourth
fingers.
The other major problem with pregnancies affected
by triploidy is hydatidiform molar changes in placental
tissue. A hydatidiform mole is a proliferation, or
overgrowth of placental tissue, such that there is
over production of the hormones of pregnancy and
often vaginal bleeding early in pregnancy, present
like a miscarriage. Molar changes in the placenta
can co-exist with an on-going pregnancy, but more
commonly there is no fetus in these pregnancies,
and they are managed by evacuation of the uterus
and followed up with hormone analysis to ensure they
have not recurred.
Suspicions of a viable pregnancy affected by polyploidy
are usually first raised by fetal growth failure,
which happens early in pregnancy and is severe. Structural
anomalies including cardiac malformations can occur,
but many cases with have no obvious structural abnormality
on ultrasound assessment. If caesarean section delivery
is being contemplated for severe growth restriction
it is wise to consider chromosome analysis, if circumstances
permit. If triploidy, or another lethal diagnosis
is made it is logical to avoid caesarean section
delivery if possible, accepting the inevitability
of the death of the baby.
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POSTNATAL
Most cases are lost spontaneously in the second
or third trimester but some liveborn and die in the
neonatal period. Liveborn infants are severely retarded
and other associated anomalies include craniofacial
abnormalities, brain anomalies, and eye defects.
Affected males have genital anomalies including hypospadias
and cryptorchidism.
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WEST MIDLANDS
DATA
To be added
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