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Early embryo mortality in natural human reproduction: What the data say.

Jarvis, Gavin E. (2017) Early embryo mortality in natural human reproduction: What the data say. F1000 Research, 5. p. 2765. ISSN 2046-1402

Item Type: Article


How many human embryos die between fertilisation and birth under natural conditions? It is widely accepted that natural human embryo mortality is high, particularly during the first weeks after fertilisation, with total prenatal losses of 70% and higher frequently claimed. However, the first external sign of pregnancy occurs two weeks after fertilisation with a missed menstrual period, and establishing the fate of embryos before this is challenging. Calculations are additionally hampered by a lack of data on the efficiency of fertilisation under natural conditions. Four distinct sources are used to justify quantitative claims regarding embryo loss: (i) a hypothesis published by Roberts & Lowe in  is widely cited but has no practical quantitative value; (ii) life table analyses give consistent assessments of clinical pregnancy loss, but cannot illuminate losses at earlier stages of development; (iii) studies that measure human chorionic gonadotrophin (hCG) reveal losses in the second week of development and beyond, but not before; and (iv) the classic studies of Hertig and Rock offer the only direct insight into the fate of human embryos from fertilisation under natural conditions. Re-examination of Hertig's data demonstrates that his estimates for fertilisation rate and early embryo loss are highly imprecise and casts doubt on the validity of his numerical analysis. A recent re-analysis of hCG study data concluded that approximately 40-60% of embryos may be lost between fertilisation and birth, although this will vary substantially between individual women. In conclusion, natural human embryo mortality is lower than often claimed and widely accepted. Estimates for total prenatal mortality of 70% or higher are exaggerated and not supported by the available data.

Jarvis (2017) Early embryo mortality in natural human reproduction - what the data say [version 2; referees - 2 approved 1 approved with reservations] F1000.pdf - Published Version
Available under License Creative Commons Attribution.

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Depositing User: Gavin Jarvis


Item ID: 14412
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ISSN: 2046-1402
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ORCID for Gavin E. Jarvis: ORCID iD

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Date Deposited: 25 Jan 2022 12:39
Last Modified: 25 Jan 2022 12:45


Author: Gavin E. Jarvis ORCID iD

University Divisions

Faculty of Health Sciences and Wellbeing > School of Medicine


Sciences > Biomedical Sciences
Sciences > Health Sciences

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