Early Pregnancy Failure 早期妊娠失败

分类:医学文献 40 0

Pregnancy covers a wide and diverse spectrum of development starting with fertilization and ending in birth. Pregnancy failure, otherwise termed as pregnancy loss or miscarriage, can occur at different stages during this process and many different pathophysiological mechanisms may be implicated. Because this is a spectrum of development, defining the individual stages of pregnancy can be quite challenging. Nevertheless, early pregnancy commonly refers to the pregnancy stage following implantation and during the first trimester. This can be divided further into: (i): preclinical pregnancies that are only identifiable by raised serial HCG measurements, and (ii) clinical pregnancies for which ultrasound or histological evidence of a gestation can be demonstrated.


In the past, focus was given primarily to those pregnancy failures occurring after a clinically recognized gestation, as preclinical pregnancy losses would commonly go unnoticed or present merely as a late period. However, with the development of over-the-counter pregnancy testing kits for early pregnancy recognition, and the widespread use of ART, the focus of interest in pregnancy failure has gradually shifted to the earlier stages of gestation. As a result, it has become increasingly evident that even women with normal fertility appear to have a large number of pregnancy losses occurring at a very early gestational stage.


Roberts and Lowe were among the first to demonstrate the scale of early pregnancy wastage, by using the registered number of births in England and estimating the number of fertile ovulatory cycles in married couples having unprotected intercourse. They calculated that only 22% of cycles exposed to the risk of pregnancy actually resulted in a live birth (1). Because the sporadic miscarriage rate of pregnancies is far less than 78%, this finding implied that the vast majority of pregnancies were being lost at a very early stage, before they were clinically recognized. In fact, a review of the literature suggests that of all pregnancies, approximately 30% fail prior to implantation, a further 30% fail following implantation but prior to clinical evidence of pregnancy, and about 10% suffer clinical miscarriages. This means that only 30% of all conceptions in fertile women will result in a live birth (2).


References 数据参考:

1. Roberts CJ, Lowe CR. Where have all conceptions gone ? Lancet 1975; 1:498-499

2. Macklen NS, Geraedts JP, Fauser BC. Conception to ongoing pregnancy : the “black box” of early pregnancy loss. Hum Reprod Update 2002; 8:333-343.

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