Epidemiology Branch, National Institute of Environmental Health Sciences, National Institutes of Health, Durham, NC, USA.
Center for Assisted Reproduction, Bedford, TX, USA.
Hum Reprod. 2020 Apr 28;35(4):743-750. doi: 10.1093/humrep/deaa048.
What proportion of fertilized human ova are lost before implantation?
An estimated 40 to 50% of fertilized ova fail to implant.
Preimplantation loss is not detectable with current technology. Published estimates of preimplantation loss range from 10 to 70%.
STUDY DESIGN, SIZE, DURATION: We combine data from epidemiologic, demographic, laboratory and in vitro fertilization studies to construct an empirical framework for the estimation of preimplantation loss. This framework is summarized in a user-friendly Excel file included in supplement.
PARTICIPANTS/MATERIALS, SETTING, METHODS: We draw from multiple sources to generate plausible estimates of fecundability, sterility, transient anovulation, intercourse patterns and the proportion of ova fertilized in the presence of sperm. We combine these estimates to generate a summary estimate of preimplantation loss. This estimate can be considered an average for couples in their prime reproductive years.
Under a plausible range of assumptions, we estimate that 40 to 50% of fertilized ova fail to implant.
LIMITATIONS, REASONS FOR CAUTION: A crucial factor in estimating preimplantation loss is the probability that an ovum will be fertilized when exposed to sperm. Human data are available only from in vitro fertilization (IVF), which may not accurately represent events in vivo. We therefore assume a range of in vivo fertilization rates, from 64% (human IVF data) to 90% (mouse data).
Our estimate of preimplantation loss takes into account the biological processes relevant to fertilization and loss. Using this empirical basis for estimation, we find support for the usual assumption that risk of loss is highest in the earliest days following fertilization. Furthermore, this framework can provide improved estimates as better reproductive data become available. To the extent that our estimates are accurate, more fertilized ova are apparently lost in vitro than in vivo, suggesting that further improvements in IVF success rates may be possible.
STUDY FUNDING/COMPETING INTEREST(S): This study was supported by the Intramural Program of the National Institute of Environmental Health Sciences, NIH. Professor Adashi serves as Co-Chair of the Safety Advisory Board of Ohana Biosciences, Inc. The other authors have no competing interests.
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受精的人类卵子在着床前有多大比例会丢失？
估计有 40%到 50%的受精卵未能着床。
目前的技术无法检测到着床前的损失。已发表的着床前损失估计值范围在 10%至 70%之间。
研究设计、规模、持续时间：我们结合流行病学、人口统计学、实验室和体外受精研究的数据，构建了一个用于估计着床前损失的经验框架。该框架总结在补充材料中一个易于使用的 Excel 文件中。
参与者/材料、设置、方法：我们从多个来源获取数据，以生成生育能力、不育、短暂性排卵障碍、性交模式和存在精子时卵子受精比例的合理估计值。我们将这些估计值结合起来，得出着床前损失的综合估计值。这个估计值可以被认为是处于最佳生殖年龄的夫妇的平均值。
在一系列合理的假设下，我们估计 40%到 50%的受精卵未能着床。
局限性、谨慎的原因：估计着床前损失的一个关键因素是卵子在暴露于精子时受精的概率。人类数据仅来自体外受精（IVF），这可能无法准确代表体内事件。因此，我们假设了一系列体内受精率，从 64%（人类 IVF 数据）到 90%（老鼠数据）。
我们对着床前损失的估计考虑了与受精和损失相关的生物学过程。使用这种基于经验的估计方法，我们发现支持这样一个常见假设，即在受精后最早的几天内，损失的风险最高。此外，随着更好的生殖数据的出现，这个框架可以提供更好的估计值。在我们的估计值准确的情况下，体外受精中丢失的受精卵显然比体内受精中丢失的更多，这表明体外受精成功率的进一步提高可能是可行的。
研究资金/利益冲突：这项研究得到了美国国立环境卫生科学研究所内部计划的支持。Adashi 教授担任 Ohana Biosciences, Inc. 安全顾问委员会的联合主席。其他作者没有利益冲突。
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