The word abortion derives from the Latin aboriri–to miscarry. Abortion is defined as the spontaneous or induced termination of pregnancy before fetal viability. It is thus appropriate that miscarriage and abortion are terms used interchangeably in a medical context. But, because popular use of abortion by laypersons implies a deliberate intact pregnancy termination, many prefer miscarriage for spontaneous fetal loss. Both terms will be used throughout this chapter.
Defining viability has significant medical, legal, and social implications as this definition provides the line that separates abortion from preterm birth. It is usually defined by pregnancy duration and fetal birthweight for statistical and legal purposes. The National Center for Health Statistics, the Centers for Disease Control and Prevention (CDC), and the World Health Organization (WHO) all define abortion as any pregnancy termination—spontaneous or induced—prior to 20 weeks’ gestation or with a fetus born weighing <500 g. Confusion may be introduced by state law criteria that define abortion more widely.
Technologic developments have revolutionized current abortion terminology. Transvaginal sonography (TVS) and precise measurement of serum human chorionic gonadotropin (hCG) concentrations help to identify extremely early pregnancies and to clarify intrauterine versus ectopic location. Ubiquitous application of these practices makes it possible to distinguish between a chemical and a clinical pregnancy. Another term, pregnancy of unknown location—PUL, aids the goal of early identification and management of ectopic pregnancy (Barnhart, 2011). Management options for ectopic gestation are described in Chapter 7. Of intrauterine pregnancies, those that end in a spontaneous abortion during the first trimester, that is, within the first 126/7 weeks of gestation, are also termed early pregnancy loss or early pregnancy failure.
Approximately half of first-trimester miscarriages are anembryonic, that is, with no identifiable embryonic elements. The previous term blighted ovum for these pregnancies has fallen out of favor. The remaining pregnancies are embryonic miscarriages, which may be further grouped as either those with chromosomal anomalies (aneuploid abortions) or those with a normal chromosomal complement (euploid abortions).
Common terms used to describe pregnancy losses are listed here and will be discussed in this chapter. They include:
Spontaneous abortion—this category includes threatened, inevitable, incomplete, complete, and missed abortion. Septic abortion is used to further classify any of these that are complicated by infection.
Recurrent abortion—this term is variably defined, but it is meant to identify women with repetitive spontaneous abortions.
Induced abortion—this term is used to describe surgical or medical termination of a live fetus that has not reached viability.
More than 80 percent of spontaneous abortions occur during the first 12 weeks of gestation (American College of Obstetricians and Gynecologists, 2015). With first trimester losses, death of the embryo or fetus nearly always precedes spontaneous expulsion. Death of the conceptus is usually accompanied by hemorrhage into the decidua basalis. This is followed ...