Christopher Chen Oocyte Biology Research Laboratory, UQ Centre for Clinical Research, The University of Queensland, Brisbane, Herston 4029, Queensland, Australia.
Semin Reprod Med. 2020 Jan;38(1):21-28. doi: 10.1055/s-0040-1721377. Epub 2020 Nov 24.
Infertility is described as unexplained when pregnancy does not occur despite ovulation, patent Fallopian tubes, and normal semen parameters. Oocyte developmental competence (or quality) is rate-limiting for pregnancy success as oocytes provide virtually all the cellular building blocks including mitochondria required during embryogenesis. However, available tests estimate oocyte numbers (anti-Müllerian hormone, follicle-stimulating hormone and antral follicle count) and ovulation (luteal phase serum progesterone) but not the third, and most pivotal, oocyte-specific parameter, quality. Severe depletion of the follicular reserve manifests as premature ovarian insufficiency and is an obvious cause of anovulation with overt symptoms and clear diagnostic criteria. In contrast, there are no biomarkers of poor oocyte quality other than through in vitro fertilization when readouts of oocyte quality such as preimplantation embryo development can be assessed. The most common cause of poor oocyte quality is natural aging, which is strongly tied to reduced oocyte mitochondrial efficiency and increased oxidative stress. In younger women, quality may also be impaired due to accelerated aging or sporadic genetic mutations which cause severe defects during oocyte and embryo development. Thus, poor oocyte quality often provides an explanation for infertility, but because it cannot be measured using conventional tests, many cases of infertility are often incorrectly labeled "unexplained." Since female age remains the best predictor of oocyte quality, age over 37 years should be considered an independent diagnostic criterion.
当尽管排卵、输卵管通畅且精液参数正常，但仍未怀孕时，就会被描述为不孕。卵母细胞的发育能力（或质量）是妊娠成功的限速因素，因为卵母细胞提供了胚胎发生过程中几乎所有的细胞构建块，包括线粒体。然而，现有的测试仅估计卵母细胞的数量（抗苗勒氏管激素、促卵泡激素和窦卵泡计数）和排卵（黄体期血清孕激素），而无法评估第三个也是最重要的卵母细胞特异性参数，即质量。卵泡储备的严重耗竭表现为卵巢早衰，这是无排卵的明显原因，有明显的症状和明确的诊断标准。相比之下，除了体外受精之外，没有其他方法可以评估卵母细胞质量，如胚胎植入前的发育情况，除了体外受精之外，没有其他方法可以评估卵母细胞质量。卵母细胞质量差的最常见原因是自然衰老，这与卵母细胞线粒体效率降低和氧化应激增加密切相关。在年轻女性中，由于加速衰老或零星的基因突变导致卵母细胞和胚胎发育过程中出现严重缺陷，质量也可能受损。因此，卵母细胞质量差通常可以解释不孕，但由于无法通过常规测试进行测量，因此许多不孕病例通常被错误地标记为“不明原因”。由于女性年龄仍然是卵母细胞质量的最佳预测因素，因此年龄超过 37 岁应被视为独立的诊断标准。
