Threatened abortion approximately affect 20% of pregnancies
and 50% of those will end up in miscarriage.
It has also been associated with poor obstetric outcome such as preterm
labor, low lying placenta, low birth weight and PROM.
The uncertainty of prognosis makes it a challenging task for
healthcare professionals.Various biomarkers have been used, with variable results to predict
the prognosis of bleeding in early pregnancy.
This systemic review and meta-analysis was published in the
forthcoming issue of Human Reproduction update, it aims to determine the diagnostic
accuracy of various biomarkers.
A total of 19 studies were found after electronic searching
of databases to determine outcomes for women with threatened abortion at 5–23
weeks gestational age.
15 studies (including 1263 women) were found eligible using
QUADAS-2 (Quality Assessment for Diagnostic Accuracy Studies-2: A Revised Tool)
to include in the qualitative data assessment.
The biomarkers that were looked into included serum
progesterone, hCG, pregnancy associated plasma protein A, estradiol and cancer
antigen 125 (CA 125).
Interestingly, serum CA 125 appeared to be the most
promising marker (n = 648 women, 7 studies), whereas serum
progesterone and hCG are less useful once fetal viability is established.
CA-125 is a glycoprotein and its origin is uncertain during
pregnancy. It arises during the first trimester and return to a non-pregnancy
range in late pregnancy.
CA 125 showed a sensitivity of 90% (95% confidence interval
(CI) 83–94%), specificity of 88% (95% CI 79–93%), positive likelihood ratio of
7.86 (95% CI 4.23–14.60) and negative likelihood ratio of 0.10 (95% CI 0.06–0.20).
The inverse of negative likelihood ratio was 9.31 (95% CI 5–17.1) indicating
that a negative test is likely to identify those who are likely to continue
with the pregnancy.
Nevertheless, when vaginal
bleeding had been present for 3 days or more and there was high maternal serum
CA125 activity, the abortion risk was found to be 100%.
Since this was a qualitative analysis, no cut-off value for
CA125 was determined but in most studies patients who eventually aborted had
values of CA-125 more than 125 IU/ml while the control had a value not more
than 93 IU/ml.
A rising value of CA 125 combined with gestational sac diameter
that does not correspond to the pregnancy dating is highly significant in
predicting the prognosis.
Serum estradiol was the next best marker with a sensitivity
of 45% (95% CI 6–90%), a specificity of 87% (95% CI 81–92%), a positive
likelihood ratio of 3.72 (95% CI 1.01–13.71) and a negative likelihood ratio of
0.62 (95% CI 0.20–1.84).
References:
https://humupd.oxfordjournals.org/content/22/2/228.abstract
https://www.researchgate.net/publication/21703609_The_prognostic_significance_of_maternal_serum_CA125_measurement_in_threatened_abortion.
http://www.ncbi.nlm.nih.gov/pubmed/12235698
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