Recurrent pregnancy loss (RPL) is a devastating reproductive
problem affecting approximately 5% of couples trying to conceive. Genetic factors are reviewed in
terms of random numerical chromosome errors in miscarriage specimens and
carriers of structural chromosome rearrangements that may result in
unbalanced chromosome errors in pregnancies.
In 1975, Boue et al
reported that 60% of miscarriages
were due to numeric cytogenetic abnormalities, specifically aneuploidies or
polyploidies, based on cytogenetic analyses of 1500 miscarriages. They
proposed that miscarriage
occurred on the basis of natural selection; pregnancies with numeric cytogenetic
abnormalities were generally not compatible with life, and therefore ended in
miscarriage. Edmonds et al and Wilcox et al, estimated that 30 to 50% of all pregnancies
are lost prior to 6 weeks gestation, and of these, 70% are due to numeric
cytogenetic errors..
Pregnancy demise between 6 and 10 weeks of gestation occurs
in approximately 15% of
clinical pregnancies, of which 50% are due to numeric cytogenetic errors.
After 10 weeks of gestation, pregnancy loss is infrequent, estimated at
approximately 2 to 3%, of which only 5 to 6% are due to numeric cytogenetic
errors. Only 0.6% of term deliveries will have a cytogenetic abnormality, most
often trisomy 21, 18, or 13, or a sex chromosome aneuploidy
, genetic
factors have been reviewed in terms of random numerical chromosome errors in
miscarriage specimens and carriers of structural chromosome rearrangements
that may result in unbalanced
chromosome errors in pregnancies.
What is skewed X-chromosome inactivation?? Ans:- Recently,
research has generated interest in genetic markers for recurrent loss such as skewed
X-chromosome inactivation and human leukocyte antigen-G polymorphisms. Assisted
reproductive technologies (specifically, preimplantation genetic diagnosis)
have been offered to couples with recurrent pregnancy loss; however, more data
need to be evaluated before routine use can be advocated. Management of genetic
factors in RPL should include therapy based
on the highest level of evidence, genetic counseling, and close monitoring of
subsequent pregnancies.
genetic
diagnosis
Recurrent pregnancy loss, a devastating reproductive
problem, affects approximately 5% of couples trying to conceive. Although much research has sought to determine causation,
just a handful of factors have been found to be associated with this
reproductive disorder.
Observations on the inefficiency of reproduction prompted researchers
to assess the cytogenetics of miscarriages.
In 1975, Boue et al reported
that 60% of miscarriages were due to numeric cytogenetic abnormalities,
specifically aneuploidies or polyploidies, based on cytogenetic analyses of
1500 miscarriages. They proposed that miscarriage occurred on the basis of
natural selection; pregnancies with numeric cytogenetic abnormalities were
generally not compatible with life, and therefore ended in miscarriage.
Additional epidemiological studies have confirmed the
original work of Boue et al .Based on
the pioneering works of Edmonds et al[and Wilcox et al. it is estimated that 30
to 50% of all pregnancies are lost prior to 6 weeks gestation, and of these,
70% are due to numeric cytogenetic errors. Pregnancy demise between 6 and 10
weeks of gestation occurs in approximately 15% of clinical pregnancies, of
which 50% are due to numeric cytogenetic errors. After 10 weeks of gestation,
pregnancy loss is infrequent, estimated at approximately 2 to 3%, of which only
5 to 6% are due to numeric cytogenetic errors. Only 0.6% of term deliveries
will have a cytogenetic abnormality, most often trisomy 21, 18, or 13, or a sex
chromosome aneuploidy
These statistics are based on studies in the general
reproductive population. Human reproduction appears to be an inefficient
process due to errors in meiosis or somatic mitosis, which result in a
nonviable pregnancy loss due to a cytogenetic abnormality. Whether the
frequency of miscarriages with cytogenetic abnormalities is similar or
increased in couples with recurrent pregnancy loss remains unanswered at this
time. If the risk of recurrence is increased, a role for preimplantation
genetic diagnosis may exist. Conversely, if the risk of recurrence is similar
to that of the general reproductive population, such technology would be
ineffective in improving the live birth rate in couples with reproductive loss.
Numeric and
structural cytogenetic errors seen in miscarriages from couples with a history
of recurrent pregnancy loss. In addition,
literature on pregnancy outcome of translocation carriers, ascertained on the
basis of recurrent pregnancy loss, suggest such disorder. highlighted, along with its limitations. Some of
the recent molecular genetic research in the field, such as X-chromosome
inactivation and human leukocyte antigen-G (HLA-G) polymorphisms, Given that preimplantation genetic diagnosis is presently being offered in some
centers for treatment of recurrent pregnancy loss.
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