Genetics in obstetrics and gynecology / Joe Leigh Simpson [and others].

Date:
[1982], ©1982
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Licence: Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)

Credit: Genetics in obstetrics and gynecology / Joe Leigh Simpson [and others]. Source: Wellcome Collection.

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    7 Spontaneous Abortion and Fetal Wastage Many causes for spontaneous abortions have been postulated. In the past, hor¬ monal imbalance, maternal overexertion, and exposure to exogenous factors (e.g., viruses) were considered the principle causes. However, chromosomal aberrations are now known to be associated with at least 50 percent of first trimester spontaneous abortions (Boué & Boué, 1974; Boué et al., 1975a; Laur- itsen, 1976). Nongenetic factors are doubtless responsible for some abortions (Elias & Simpson, 1980a; Glass & Golbus, 1978; Simpson, 1981b). In this chapter we shall limit our discussion to cytogenetic factors, the role of which is best appreciated by considering the losses in the different stages of embryonic de¬ velopment. PRECLINICAL STAGES Although few studies have considered the extent to which embryos are lost prior to clinical recognition of pregnancy, available data suggest that the frequency of morphologic abnormalities is very high among preimplanted and early-implanted embryos. Abnormalities affecting preimplantation and early- implantation stages (less than three weeks of embryonic life) usually escape clinical detection. The etiology of early losses is usually abnormal embryonic development. Indeed, Hertig and colleagues have shown that morphologic abnormalities exist in very young embryos recovered from the Fallopian tubes, uterine cavities, and endometria of women undergoing elective hysterectomy (Hertig et al., 1959; Hertig, 1975). Dates of ovulation were deduced on the basis of basal body temperature elevation, and coital times were recorded. All women were of proven fertility, and mean age was 33 years. Four of eight preimplanted embryos recovered were morphologically abnormal. In the investigators' opinion, the 121