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How to define the "Poor Ovarian Response"?


"Why do I have only a few follicles developed in this cycle?"


"Why my stimulated follicles seems less than the last cycle?"


Some patients had poor response to the controlled ovarian stimulation, and thus they underwent the treatment almost per month to collect available oocytes. These patients were defined as the group of potential " poor ovarian response (POR)." In 2011, the European Society of Human Reproduction and Embryology (ESHRE) defined these patients based on the standard criteria, which were called "Bologna Criteria,"



At least two of the following three features must be present:
i.
Advanced maternal age ( 40 years), or any other risk factors for POR
ii.
A previous POR ( 3 oocytes with a conventional stimulation protocol)
iii
An abnormal ovarian reserve test (ORT, i.e. AFC < 5-7 or AMH < 0.5-1.1 ng/ml)

However, the clinical identification of POR are still very difference, since not all the patients with POR met the above description.


In 2014, an Australian researcher, Venetis, indicated that the Bologna Criteria can't define the POR group clearly due to its complicated statistics. Another researcher, Papathanasiou, from United Kingdom, thought that the POR group shouldn't be defined by a simple dichotomy, but by an integrated assessment.
These concepts from different areas may be affected by the racial characteristics. In Taiwan, the Chang-Kung medical research group did a retrospective analysis to evaluate the applicability of Bologna Criteria to the Taiwanese POR patients,

Study subjects: the cycle with retrieval oocyte 3

Study time span: Jan, 2001 ~ Sep, 2014

Sample size: 855 cycles (under 40 years of age: 589 cycles; over 40 years of age: 266 cycles)

According to the following table, four factors displayed significant effect to the clinical outcomes: age, primary/secondary infertility, number of mature oocytes, grading of transferred embryo


They further compared the embryologic and clinical characteristics between the group over 40 years and under 40 years, and found that the maternal age was the most crucial factor in the patientsthe fertilization rate, embryo grading (blastocyst stage), implantation rate, clinical pregnancy rate were better in the group under 40 years than those in the group over 40 years.

Due to the individual diversity in the POR group defined by Bologna Criteria, the universal definition may not be appropriate to all the potential POR patients. As it mentioned above, the maternal age may be more important than the other affecting factors. Thus the applied treatments in the patients must be modified according to their age.


References:
1.  2015 TSRM: Evaluation of the Bologna criteria for women of different age: Cohort study of women with extremely low oocyte retrieval cycles.
2.  The Bologna criteria for poor ovarian response: the good, the bad and the way forward. Human Reproduction, 2014.
3.  Implementing the ESHRE ‘poor responder’ criteria in research studies: methodological implications. Human Reproduction,29(9) 1835-8, 2014.
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