In the early months of pregnancy spontaneous expulsion of the ovum is nearly always preceded by the death of the foetus. For this reason the consideration of the aetiology of abortion practically resolves itself into determining the cause of foetal death. In the later months, on the other hand, the foetus is frequently born alive, and other factors must be looked for to explain its expulsion.
—J. Whitridge Williams (1903)
In early pregnancy, miscarriage is a common event. Most early losses stem from genetic abnormalities or yet unidentified reasons. Thus, the opportunity for prevention is currently small. Women with later miscarriage or with recurrent miscarriage more likely have a repetitive cause that may be modified. In contrast to these spontaneous losses, pregnancy termination may be elected. For both induced abortion and miscarriage, management has evolved to include surgical or medical options, and providers should have an understanding of these techniques and their potential complications.
Abortion is defined as the spontaneous or induced termination of pregnancy before fetal viability. It thus is appropriate that miscarriage and abortion are terms used interchangeably. However, popular use of abortion by laypersons implies intended pregnancy termination, and many prefer miscarriage for spontaneous loss. In contrast, induced abortion describes surgical or medical termination of a live fetus that has not reached viability.
Terms used to define fetal viability and thus an abortus vary among authoritative organizations. The National Center for Health Statistics, the Centers for Disease Control and Prevention, and the World Health Organization all define abortion as pregnancy termination or loss before 20 weeks’ gestation or with a fetus delivered weighing <500 g. These criteria, however, are somewhat contradictory because the mean birthweight of a 20-week fetus is 320 g, whereas 500 g is the mean for 22 to 23 weeks (Moore, 1977). Further confusion may derive from criteria set by state laws that define abortion even more widely.
Technological developments have added to current abortion terminology. For example, precise measurement of serum human chorionic gonadotropin (hCG) concentrations can identify extremely early pregnancies. Also, transvaginal sonography allows greater inspection of failed pregnancies, but recommendations vary as to terms for: (1) early conceptions in which no products are seen sonographically, (2) pregnancies that display a gestational sac but no embryo, and (3) those in which a dead embryo is seen (Kolte, 2015; Silver, 2011). Further, incongruity exists for the term early pregnancy loss itself. Currently, the American College of Obstetricians and Gynecologists (2017c) defines this as a nonviable, intrauterine pregnancy (IUP) with either an empty gestational sac or a gestational sac containing an embryo or fetus without fetal heart activity within the first 126/7 weeks of gestation. Of other clinical terms, spontaneous abortion includes threatened, inevitable, incomplete, complete, and missed abortion. Septic abortion is used to further classify any of these that are complicated further by infection. Recurrent pregnancy loss is variably defined but is meant to identify women with repetitive miscarriage.
Other definitions help distinguish intrauterine from ectopic gestations. The term pregnancy of ...